Nitrobenzene ( F004) ( U169) 0.00013 5 25 0.195 30 0.043 Pyridine ( F005) ( D038) ( U196) 0.0003 90 120 0.78 211 0.006 Ethyl ether ( F003) ( U117)   0.3   0.002 0.30 4.30 Acetone ( F003) ( U002) 0.000002 0.7 0.05 0.001 0.75 1.73 Methanol ( F003) ( U154) 0.000002 0.2 0.02 0.0002 0.22 5.90 Butanol ( F003) ( U031)   0.8   0.005 0.81 1.61 Carbon disulfide ( F005) ( P022) 0.00007 0.08 2 0.0035 2.1 0.62 Methyl ethyl ketone ( F005) ( D035) ( U159) 0.00003 0.1 4 0.00072 4.1 0.32 Methyl isobutyl ketone ( F003) ( U161) 0.0002 0.6 42 0.007 43 0.03 Cyclohexanone ( F003) ( U057)   0.02   0.0001 0.020 64.55 2 Ethoxyethanol ( F005) ( U359) 0.000008 0.3 0.04 0.0005 0.34 3.82 Tetrachloroethylene ( F002) ( D039) ( U210) 0.0001 0.02 0.2 0.003 0.22 5.83 Isobutyl alcohol ( F005) ( U140)   0.3   0.0015 0.30 4.31 Cresols a ( F004) ( D023 to D026) ( U052)   3   0.16 3.2 0.41 Chlorobenzene ( F002) ( D021) ( U037) 0.0004 0.02 3.6 0.003 3.6 0.36 Ethyl acetate ( F003) ( U112)   0.08   0.00042 0.080 16.17 Trichlorofluoromethane ( F002) ( U121) 0.00007 0.0009 0.08 0.00009 0.081 16.05 Dichlorodifluoromethane ( F001) ( U075) 0.0002 0.003 0.6 0.0002 0.60 2.16 Table 15 Risk Loading Threshold Results Constituent Relative Risk ( as HQ or carcinogenic risk), based on disposal of 1.3 kg contaminant/ day in a landfill Resulting Risk Loading Threshold ( kg/ d, per landfill) From Direct Inhalation From Ground Water Ingestio n From Indirect Ground Water Exposure ( Inhalation) From Indirect Ground Water Exposure ( Dermal) Sum of Risk from Pathways 99 1,2 Dichlorobenzene ( F002) ( U070) 0.000002 0.0008 0.1 0.0005 0.10 12.84 Ethyl benzene ( F003) 0.000009 0.007 0.1 0.002 0.11 11.95 Toluene ( F005) ( U220) 0.00005 0.006 0.6 0.001 0.61 2.14 1,1,2 Trichlorotrifluoroethane ( F002) 0.000002 0.00002 0.0032 0.000003 0.0032 403.37 1,1,1 Trichloroethane ( F002) 0.00004 0.002 0.08 0.0002 0.082 15.81 Xylenes ( total) b ( F003) ( U239) 0.00001 0.0002 0.21 0.00007 0.21 6.18 Carcinogens ( Risk expressed as carcinogenic risk)

Methylene chloride ( F002) ( U080) 4x10 9 1.5x10 5 2.1x10 6 2.7x10 7 I= 1.7x10 5 C= 3.3x10 5 0.39 1,1,2 Trichloroethane ( F002) ( U227) 3x10 8 7x10 6 4x10 6 4x10 7 I= 1.1x10 5 C= 1.6x10 5 0.83 Carbon tetrachloride ( F001) ( D019) ( U211) 9x10 8 2.6x10 6 8x10 7 4x10 7 I= 3.8x10 6 C= 4.3x10 6 3.0 2 Nitropropane ( F005) ( U171) 9x10 6   4x10 3   I= 4x10 3 C= 4x10 3 0.003 Benzene c ( F005) ( D018) ( U019) 5x10 8 1.3x10 5 7x10 6 1.1x10 6 I= 2.1x10 5 C= 5.4x10 5 0.24 Trichloroethylene ( F002) ( D040) ( U228) 7x10 9 2.7x10 7 1.5x10 7 5x10 8 I= 4.7x10 7 C= 4.7x10 7 27.66 For ` Sum of Risk Pathways' for carcinogens, ` I' refers to risks from the individual compound, while ` C' refers to the sum of risks from all other carcinogenic compounds of less toxicity. The risk loading threshold is based on the higher, ` C' results. Source of relative risk results: U. S. Environmental Protection Agency. Estimating the Risk from the Disposal of Solvent Contaminated Shop Towels and Wipes in Municipal Landfills." March 1999. The risk loading thresholds were calculated from these results. Relative risk shows HQ or carcinogenic risks resulting from disposal of 1.3 kg/ day in a landfill, which was necessary to conduct a ` forward' calculation. Risk loading thresholds show disposal rate that results in an HQ= 1 or carcinogenic risk = 10 5. This was calculated by dividing 1.3 kg/ day by the sum of risk from all pathways ( which based on a 1.3 kg/ day disposal rate), and multiplying by HQ= 1 or carcinogenic risk = 10 5. Shading indicates the dominant exposure pathway. a. The isomers o, m, and p cresols were evaluated individually; risks from p cresol were greatest and presented here. b. The isomers o and m xylene, and total xylenes, were evaluated individually; risks from total xylenes were greatest and presented here. 100 c. Updated toxicity data for benzene on IRIS shows slightly lower carcinogenic properties from inhalation compared to those used here. Because indirect inhalation exposure is not a ` driver' in this analysis when using the older toxicity information, the toxicity reassessment should not have a significant effect on this analysis.

V. B. 3. Estimating Total Risks from All Sources Disposing Solvent Contaminated Industrial Wipes in a Landfill V. B. 3. a. What Data was Used to Estimate Risk?

The above analysis calculated the maximum quantity of F listed solvent constituents that can be disposed each day in a landfill such that resulting risks to human health would equal an HQ of 1 or a carcinogenic risk of 10 5. Using these risk loading thresholds, EPA compared the thresholds to the estimated quantity of each solvent expected to result from disposing industrial wipes. To conduct the analysis, EPA looked at the following seven categories of data.

Number of Disposable Industrial Wipes Used Annually by Small and Large Quantity Generators The number of disposable industrial wipes used nationwide was estimated in 2001 to be 1.009 billion, consisting of 49.8 million printer wipes and 959.2 million non printer wipes. These estimates were made using data supplied by a trade association ( Association of the Nonwoven Fabrics Industry) for 1997. These were updated to 2001 based on the average annual economic growth using the ` Industrial Production Index' for each of 13 industries which use wipes.

Number of Days Landfill Operates; Number of Landfills Nationally; Concentration of Facilities Sending their Wipes to a Single Landfill For this analysis, EPA also distinguished between printer wipes and non printer wipes since the printing industry appears to use much larger amounts of wipes and larger amounts of solvent on each wipe compared to most other industries. Also, because certain parts of the country have more generators per landfill than other parts of the country, EPA introduced the variable " concentration of facilities sending their wipes to a single landfill" to account for this situation.

In the U. S., there were 2,514 landfills in 1997 (` The State of Garbage in America,' BioCycle, April 1998). This is an average of about 50 landfills per state. However, some areas of the country are expected to have fewer landfills. The five states with the fewest number of landfills ( Connecticut, Rhode Island, Delaware, Vermont, and Maine) have a total of 24 landfills, or an average of about 5 landfills per state. This is about ten times less than the national average. This factor of ten is incorporated into the risk screening assessment as a high end parameter. This parameter is intended to identify regional effects where a relatively large number of generators is using a relatively small number of landfills, resulting in a higher landfill loading rate of solventcontaminated industrial wipes in certain localities.

EPA assumed the landfills operate 350 days per year.

Percentage of Disposable Industrial Wipes Containing F Listed Solvents The likelihood that a facility would use an F listed solvent was estimated to be 35 percent. 20Based on a survey of used wipe disposal practices for printers, 18 percent of facilities indicated that they used methyl ethyl ketone, 27 percent reported using acetone, 20 percent reported using xylene, and 20 percent reported using toluene. Based on this data ( all of which represent F listed solvents), EPA assumed that 25 percent of facilities use F listed solvents.

21 The basis for this has been information from the printing industry identifying that 10 percent of solvents identified in the industry were nonhazardous, 10 percent were listed, and 80 percent were characteristic. Characteristic wastes comprise TC and ignitable only wastes; EPA assumed that a portion ( 10 percent) are TC.

101 This assumes that facilities use F listed solvents 25 percent of the time and toxicity characteristic ( TC) solvents 10 of the time. The basis for the 25 percent value is data from the Screenprinting and Graphic Imaging Association International ( SGIA 1998a). 20 The 10 percent value is an assumption also based on information from the printing industry. 21 Percentage of Wipes that Could Contain a Given F listed Solvent The likelihood that the F listed solvent would contain the subject contaminant is highly uncertain because representative data are not available. Each constituent was assigned a value of 10 percent or 50 percent. This signifies that if a facility actually uses an F listed solvent ( which, as described above, is assumed to only occur at 35 percent of facilities anyway), then this is the probability that the subject contaminant would be present. These numbers were arbitrarily selected. The following approach was used in assigning a value of 10 percent or 50 percent to each constituent:

° Data characterizing solvent composition in three sectors ( printing, furniture, autobody repair) were prepared as an addendum to SAIC, " Use and Management Practices of Solvent Contaminated Industrial Shop Towels," Final Report, 1997. A total of 15 different F listed constituents were found in the solvents identified. Each of these constituents were assigned a value of 50 percent since their use in solvents is documented. These 15 constituents are acetone, butanol, o cresol, isobutanol, methanol, methyl ethyl ketone, ethyl acetate, tetrachloroethylene, cyclohexanone, ethyl benzene, toluene, 1,1,1 trichloroethane, trichlorofluoromethane, xylenes, and methylene chloride.

° Three compounds considered to be less toxic were assigned a probability of 50 percent. It was assumed that facilities would use these less toxic components preferentially over more toxic components. These three compounds are 1,1,2 trichlorotrifluoroethane, m xylene, and o xylene. ( Note that data for the xylene isomers are not presented in Table 15.)

° The remaining constituents were assigned a value of 10 percent.

Concentration of Each F Listed Solvent The percentage of contaminant likely to be present in a solvent also has high uncertainty and variability. A solvent can contain contaminant concentrations ranging from less than 1 percent 102 to 100 percent. Data characterizing solvent composition in three sectors ( printing, furniture, and autobody repair) were prepared as an addendum to SAIC, " Use and Management Practices of Solvent Contaminated Industrial Shop Towels," Final Report, 1997. A total of 15 different F listed constituents were found in the solvents identified ( these 15 constituents are identical to those identified above). For each constituent in each industry, a range was developed using the data in the SAIC ( 1997) report. For constituents with no data, an arbitrary range of 5 to 50 percent was used which corresponded, approximately, to the range for most constituents with composition data. The arbitrary percentage range is uncertain because the data are not representative of the evaluated industries. For this analysis an average ( rather than a maximum) concentration was used. The average concentration was calculated as the arithmetic mean between the two extremes of the range. A ` floor' of ten percent was established for each constituent to be consistent with the F001 to F005 definition. For each of the 30 constituents, the concentrations ranged from 10 to 51 percent; the exact concentration used was constituent dependent.

Amount of Solvent Contained on Each Wipe This analysis assumed that dry wipe weight was 25 grams. However, the amount of solvent contained on each wipe is dependent on industry type. It was assumed that wipes from printer facilities contain 25 grams of solvent whereas wipes from non printer facilities contain only 12.5 grams of solvent. Therefore, a solvent to wipe ratio of 1 for printers and 0.5 for non printers was used.

This estimate was derived from data collected from EPA site visits. These amounts were calculated by first weighing and measuring the dry wipe, giving it to the worker to add solvent to it, and measuring the weight a second time. The data were used to calculate a ratio of solvent added to dry wipe weight; a high ratio indicates that a large amount of solvent is used as compared to the size and weight of the wipe. As expected, there is wide variability in the amount of solvent placed on all types of wipe. Some of the facilities visited apply relatively small amounts of solvent to each wipe ( i. e., the solvent/ wipe ratio ranges from 0.1 to 1). Other facilities used solvent in a ratio between 2 and 3, while one facility had a ratio of 7, representing a saturated wipe. Conclusions from this investigation were that ( 1) within a facility or industry, different tasks require different quantities of solvent; and ( 2) the ratios for facilities within the printing industry were generally higher than the ratios from other facilities, such as those in the auto body industry. The selected solvent quantities represent the middle of the distribution, as determined from the site visits.

Percentage of Wipes that will be Landfilled ( Rather than Combusted)

The percentage of disposable industrial wipes that are actually managed in a landfill was assumed to be 78 percent. This is equal to the quantity of municipal solid waste landfilled ( 118 million tons in 1995) divided by the quantity of municipal solid waste discarded ( 152 million tons in 1995). The difference is the quantity combusted ( EPA 1997b).

Finally, the results of these calculations were converted to a landfill basis, for use in conjunction with the risk loading thresholds. This conversion accounts for multiple generators using a single landfill. 103 V. B. 3. b. Summary of Assumptions Used to Estimate Risk Table 16 summarizes the assumptions used for this analysis. Note that with the exception of solvent concentration and percentage of wipes containing a specific solvent, all of the other assumptions discussed above are fixed regardless of the contaminant. 104 Table 16 Variable and Assumptions Used in Estimating Total Risks from Disposing of Solvent Contaminated Industrial Wipes in a Landfill Variable Assumptions Factors Affecting Contaminant Quantity Number of Disposable Industrial Wipes Used Annually Estimated at 1.009 billion wipes using Census data and trade association data Percentage of wipes containing F listed solvents Only 35 percent of facilities are assumed to use F listed solvent. Other solvents are not evaluated ( as discussed in section V. B. 1).

Percentage of wipes that could contain a given F listed solvent Each constituent was assigned a probability of 10 or 50 percent of being present in a solvent, based on usage information from site visits, etc.

Concentration each F listed solvent Constituents were assumed to be present as a mixture, with concentration ranging from 10 to 51 percent based on site visits and Material Safety Data Sheets ( MSDSs)

Amount of solvent contained on each wipe Disposables from printers were assumed to have a solvent weight of 25 grams, whereas disposables from non printers were assumed to have a solvent weight of 12.5 grams.

Factors Affecting the Landfill Universe Percentage of wipes that will be landfilled ( as compared to combustion) Only facilities using MSWLFs, rather than municipal waste combustors ( MWCs), were considered here. Seventy eight ( 78) percent of municipal solid waste ( MSW) is landfilled, 22 percent combusted.

Number of days landfill operates 350 days, assumed Number of landfills nationally 2,514 based on 1997 BioCycle survey data Concentration of facilities sending their wipes to a single landfill A factor of 10 was used, as a high end parameter, to account for localized effects of a relatively large number of generators clustered near a relatively small number of landfills. 105 The overall calculation is summarized below:

1,009 million number of disposables used by LQGs and SQGs × 0.35 fraction with F listed constituents × 0.78 fraction landfilling ( rather than combusting) disposable industrial wipes × 0.1 or 0.5 fraction using given constituent × 0.1 to 0.51 fraction of constituent in solvent ( based on arithmetic average concentration) × [( 0.049 × fraction of disposables used by printers 25) + grams of solvent per wipe for a printer ( 0.951 × fraction of disposables used by non printers 12.5)] grams of solvent per wipe for a non printer × 10 concentration of facilities to a single landfill, above the national average ( high end parameter) / 350 days per year that landfill operates / 2,514 number of landfills nationwide 1.13 to 10.4 kg/ day loading to landfill, depending on the contaminant Based on the calculations, it is assumed that from 1.13 to 10.4 kg/ day of a constituent is disposed at a single landfill ( depending on the constituent).

What if Solvent Loading is Reduced by Centrifuging?

As part of this analysis, EPA also examined the potential risks assuming less solvent was present on the disposable wipe. This analysis assumes generators use an advanced solvent extraction technology, such as centrifuging, where greater than 90 percent of solvent is removed.

V. B. 4 Risks from Landfilling Disposables Results of the risks from landfilling disposables in landfills are presented in Table 17. This table presents the following information for each constituent:

° The risk loading threshold, derived in section V. B. 2. As previously described, reasons for different limits include differences in toxicity and physical/ chemical properties.

° The landfill loading, derived in section V. B. 3. This quantity is dependent on the contaminant and varies from a low of 1.13 kg/ day/ landfill for a number of contaminants, to a high of 10.4 kg/ day/ landfill for methylene chloride. As previously described, reasons for different loading between constituents include differences in the frequency of use and its concentration.

° Landfill loading, assuming a centrifuge is present. For this analysis, the landfill loadings were multiplied by 10 percent, as described in section V. B. 3. 106 ° One of three conclusions based on a comparison between the risk loading threshold and the landfill loading:

° If the risk loading threshold is greater than the landfill loading, then EPA concludes that the contaminant is unlikely to present a risk given the assumptions used in the risk assessment. The contaminant is identified as ` Acceptable.'

° If the risk loading threshold is less than the landfill loading ( even assuming a centrifuge is present), then EPA concludes that the contaminant is likely to present a risk given the assumptions used in the risk assessment. The contaminant is identified as ` Ineligible.'

° If the risk loading threshold is between the landfill loadings for centrifuged and not centrifuged wipes, then EPA concludes that the contaminant is unlikely to present a risk as long as centrifuging is conducted prior to disposal. The contaminant is identified as ` Centrifuge Required.'

In summary, Table 17 shows that of the 30 constituents evaluated, 16 constituents are acceptable, 8 are acceptable only if centrifuged beforehand, and the remaining 6 are ineligible because the projected loading is higher than the risk loading threshold. More specifically, the following constituents were found for the above three categories:

° Acceptable ( 16 constituents): carbon tetrachloride, cyclohexanone, 1,2 dichlorobenzene, dichlorodifluoromethane, 2 ethoxyethanol, ethyl acetate, ethyl benzene, ethyl ether, isobutyl alcohol, methanol, tetrachloroethylene, 1,1,1 trichloroethane, trichloroethylene, trichlorofluoromethane, 1,1,2 trichlorotrifluoroethane, xylenes.

° Centrifuge required ( 8 constituents): acetone, benzene, butanol, carbon disulfide, chlorobenzene, cresols, toluene, 1,1,2 trichloroethane.

° Ineligible ( 6 constituents): nitrobenzene, pyridine, methylene chloride, methyl ethyl ketone, methyl isobutyl ketone, 2 nitropropane. 107 Table 17 Evaluation of Disposable Solvent Contaminated Industrial Wipes for Landfilling CAS No. Constituent ( RCRA Waste Codes) Risk Loading Thresholda ( kg/ d, per landfill) Loading ( kg/ day, per landfill) Loading Assuming Centrifuging ( kg/ day, per landfill) Conclusion Noncarcinogens 67 64 1 Acetone ( F003) 1.73 4.72 0.47 Centrifuge required 71 36 3 Butanol ( F003) 1.61 2.05 0.21 Centrifuge required 75 15 0 Carbon disulfide ( F005) 0.62 1.13 0.11 Centrifuge required 108 90 7 Chlorobenzene ( F002) ( D021) 0.36 1.13 0.11 Centrifuge required 108 94 1 Cyclohexanone ( F003) 64.55 2.05 0.21 Acceptable 1319 77 3 Cresols ( F004) ( D023) ( D024) ( D025) ( D026) 0.41 1.13 0.11 Centrifuge required 75 71 8 Dichlorodifluoromethane ( F001) 2.16 1.13 0.11 Acceptable 95 50 1 1,2 Dichlorobenzene ( F002) 12.84 1.13 0.11 Acceptable 141 78 6 Ethyl acetate ( F003) 16.17 2.46 0.25 Acceptable 100 41 4 Ethyl benzene ( F003) 11.95 2.05 0.21 Acceptable 60 29 7 Ethyl ether ( F003) 4.30 1.13 0.11 Acceptable 110 80 5 2 Ethoxyethanol ( F005) 3.82 1.13 0.11 Acceptable 78 83 1 Isobutyl alcohol ( F005) 4.31 2.05 0.21 Acceptable 67 56 1 Methanol ( F003) 5.90 3.49 0.35 Acceptable 78 93 3 Methyl ethyl ketone ( F005) ( D035) 0.32 4.00 0.40 Ineligible 108 10 1 Methyl isobutyl ketone ( F003) 0.03 1.13 0.11 Ineligibleb 98 95 3 Nitrobenzene ( F004) 0.043 1.13 0.11 Ineligible 110 86 1 Pyridine ( F005) ( D038) 0.006 1.13 0.11 Ineligible 127 18 4 Tetrachloroethylene ( F002) ( D039) 5.83 4.82 0.48 Acceptable 108 88 3 Toluene ( F005) 2.14 5.54 0.55 Centrifuge required Table 17 Evaluation of Disposable Solvent Contaminated Industrial Wipes for Landfilling CAS No. Constituent ( RCRA Waste Codes) Risk Loading Thresholda ( kg/ d, per landfill) Loading ( kg/ day, per landfill) Loading Assuming Centrifuging ( kg/ day, per landfill) Conclusion 108 71 55 6 1,1,1 Trichloroethane ( F002) 15.81 9.86 0.99 Acceptable 76 13 1 1,1,2 Trichlorotrifluoroethane ( F002) 403.37 5.65 0.56 Acceptable 75 69 4 Trichlorofluoromethane ( F002) 16.05 3.80 0.38 Acceptable 1330 20 7 Xylenes ( total) ( F003) 6.18 2.05 0.21 Acceptable Carcinogens 71 43 2 Benzene ( F005) ( D018) 0.24 1.13 0.11 Centrifuge required 56 23 5 Carbon tetrachloride ( F001) ( D019) 3.02 1.13 0.11 Acceptable 75 09 2 Methylene chloride ( F002) 0.39 10.42 1.04 Ineligible 79 46 9 2 Nitropropane ( F005) 0.0033 1.13 0.11 Ineligible 79 01 6 Trichloroethylene ( F002) ( D040) 27.66 1.13 0.11 Acceptable 79 00 5 1,1,2 Trichloroethane ( F002) 0.83 1.13 0.11 Centrifuge Required a Loading threshold shows disposal rate that results in an HQ= 1 or carcinogenic risk = 10 5. b Methyl isobutyl ketone is listed for its characteristic of ignitability and therefore, when it is mixed with solid waste, is no longer considered hazardous waste unless it continues to display its characteristic. Therefore, although this assessment lists MIK as Ineligible, a wipe containing it can be disposed of in a landfill if it meets the other requirements.

V. B. 5. What High End Assumptions Are Related With this Analysis?

Separate sets of assumptions associated are with the two parts of this analysis: the assumptions regarding the loading of contaminants to the landfill and the assumptions regarding the subsequent transport and exposure. High end assumptions are summarized here. The next section, section V. B. 6, identifies areas where the analysis is uncertain or may potentially underestimate risk.

The high end assumptions identified in the analysis, as they relate to the loading of the contaminant to the landfill, include the following: 22 As part of their petition, Kimberly Clark submitted data showing the evaporation rates of certain solvents from disposable industrial wipes. SAIC ( 1997) also presents data regarding evaporation rates under a variety of conditions.

109 ° Other than centrifuging, no other removal processes are assumed to occur prior to landfilling. This includes evaporation. 22 Removal efficiencies of such processes are variable.

° The number of generators using a single MSW landfill is assumed to be ten times greater than the national average. Such an approach assumes a ` localized concentration' of generators.

Additionally, once the contaminant enters the landfill a number of additional high end assumptions are associated with fate and transport. These include the following:

° The contaminants in the waste are assumed to be available for release, not irreversibly bound to the matrix.

° Assumption of use of one of four scenarios which results in the greatest receptor well concentrations ( i. e., in this case, a small landfill).

° The DAF for groundwater transport was evaluated at the 95th percentile level in a Monte Carlo analysis.

V. B. 6. What Uncertainties and Limitations Are Related With this Analysis?

Uncertainty and limitations can be categorized according to ( 1) exposure and toxicological benchmarks, ( 2) the loading of the constituent to the landfill, and ( 3) the partitioning, transport, and exposure of the constituent once it enters the landfill. Many uncertainties, limitations, and comments regarding the predictive nature of the assessment were identified when the EPA ( 1999) report was distributed to three outside experts as a peer review.

V. B. 6. a. Overall Uncertainty EPA did not attempt to quantify total uncertainty of the analysis and thus does not know the direction or magnitude of each of the identified uncertainties. EPA did not conduct a field validation effort to identify the direction of the uncertainties. Thus, the cumulative impact of these uncertainties is unknown.

EPA did not conduct a sensitivity analysis that would identify the most sensitive parameters in the assessment. This adds some uncertainty into the modeling application because the databases and modeling methodology associated with these parameters could be reviewed for completeness and acceptability if the most sensitive parameters were identified. EPA recognizes that the " source term" assumptions associated with the landfill are likely to be uncertain because the data associated with developing these assumptions was generally limited. 110 V. B. 6. b. Uncertainty in Benchmarks and Exposure Assumptions Sources of uncertainty in toxicological benchmarks include one or more of the following: extrapolation from laboratory animal data to humans, variability of response within the human population, extrapolation of responses at high experimental doses under controlled conditions to low doses under highly variable environmental conditions, and adequacy of the database ( number of studies available, toxic endpoints evaluated, exposure routes evaluated, sample sizes, length of study, etc.). Toxicological benchmarks are designed to be conservative ( i. e., to overestimate risk) because of the uncertainties and challenges associated with condensing toxicity data into a single quantitative expression.

Another important area of uncertainty involves estimates of risks to children from carcinogenic compounds. EPA estimated the risk of developing cancer from the estimated lifetime average daily dose and the slope of the dose response curve. A cancer slope factor is derived from either human or animal data and is taken as the upper bound on the slope of the dose response curve in the low dose region, expressed as a lifetime additional cancer risk per unit exposure. However, individuals exposed to carcinogens in the first few years of life may be at increased risk of developing cancer. EPA did not adjust the cancer slope factors to account for age specific differences in exposure assumptions ( e. g., body weight). However, EPA recognizes that significant uncertainties and unknowns exist regarding the estimation of lifetime cancer risks in children. Methodologies for estimating environmental threats to children's health are relatively new. They are currently being debated within the scientific community and will continue to evolve.

Non cancer effects in children is also an area of uncertainty. Non cancer reference doses and reference concentrations for children are based on comparing childhood exposure, for which EPA has age specific data, with adult toxicity measures, where adequate age specific doseresponse data is lacking. This mismatch results in a large amount of uncertainty in the estimation of hazard quotients for children and would sometimes result in an overestimation of children's risk and sometimes in an underestimation. This issue is still under investigation in the scientific community, and no consensus has been reached.

Another uncertainty is the impact of inter individual variability in exposure. In this analysis, exposure variables ( for example, media intake rates, residence duration) are fixed for all receptors of a given type and age. Preliminary simulations suggest that variability may not be too large given the large variability of media concentrations nationally. However, with further regionalization and refinement of environmental fate and source characterization model inputs, inter individual variability in exposure could become a significant factor in model output in the future.

In addition, the analysis only considered exposure to groundwater through household uses of the water. Other potential exposures to groundwater could occur through the use of groundwater for crop irrigation and through use of surface waters fed by contaminated groundwater. EPA expects that these exposures would be significantly lower than the exposure through household use. 111 V. B. 6. c. Uncertainty in Chemical Fate and Transport Another important area of uncertainty is the transformation of chemicals that can occur either in the waste management unit or in environmental media. Once chemicals are placed in a waste management unit, this analysis assumed that various processes such as biodegradation and hydrolysis act to change the chemical. These changes result in transformation products. Often the transformation from one chemical to another results in a less toxic chemical; however, for a few chemicals, the resultant transformation products can be more toxic. The risk assessment did not model transformation products.

The risk screening assessment accounts for degradation within the landfill, although this is expected to differ on a case by case basis due to the following factors:

° Some landfills may be constructed to encourage or discourage degradation;

° The presence of a liner may slow the migration of a contaminant, in effect giving it more time to degrade within the landfill;

° While degradation in the groundwater flow path was not considered in the assessment, their varying rates of decomposition ( i. e., ` half lives') indicate that some contaminants could be expected to degrade more quickly than others in the environment.

As a result of these effects, contaminants with relatively short half lives are expected to be impacted by this uncertainty to a greater extent than contaminants that are not expected to degrade quickly. For contaminants that were not assumed to degrade or for which degradation was not assumed to occur due to lack of data ( e. g., ethyl ether), this uncertainty cannot be assessed.

In modeling the fate and transport of chemicals in groundwater, EPA did not assess complex hydrogeology such as karst or highly fractured aquifers. Some fraction of the groundwater settings in this analysis have fractured flow. In general, fractured flow in groundwater can channel the contaminant plume, thus allowing it to move faster and more concentrated than in nonfractured flow environment. This would result in higher concentrations in the groundwater.

In addition, the modeling methodology itself is another source of uncertainty, because models and their mathematical expressions are simplifications of reality that are used to approximate real world conditions and processes and their relationships. The sources of model uncertainty include relationship errors and modeling errors. Models do not include all parameters or equations necessary to express reality because of the inherent complexity of the natural environment and the lack of sufficient data to describe the natural environment. Consequently, models are based on numerous assumptions and simplifications and reflect an incomplete understanding of natural processes.

EPA selected the models used in this risk assessment based on science, policy, and professional judgment. These models were selected because they provide the information needed for this analysis and because EPA generally considers them to be state of the art science. Even 112 though the models used in the risk analyses are used widely and have been accepted for numerous applications, they each retain significant sources of uncertainty. Evaluated as a whole, the sources of model uncertainty in our analysis could result in either an overestimation or underestimation of risk.

V. B. 6. d. Uncertainty in Site Characteristics EPA was not able to directly measure many of the site characteristics ( for example, depth to groundwater; aquifer thickness; hydraulic conductivity; location of wells; behavioral characteristics of receptors) near each landfill to estimate risk. These model inputs were characterized through regional and national databases. As a result, the data used has several limitations. Overall, the use of regional and national input data rather than site based facility and environmental data could cause estimated concentrations to be low or high at a given location, with no known general bias.

In addition, the risk assessment tracks individual chemicals from waste disposed in landfills into the surrounding multimedia environment at a series of locations around the country. A variety of transport processes, including volatilization, leaching, runoff, erosion, advection, dispersion, and deposition, move chemicals from the landfills through the multimedia environment to locations where human receptors are likely to be exposed. A set of chemical specific data are required for the environmental simulation models that are used to calculate chemical fate and characterize the resulting exposures and risks.

Some of the chemical properties, such as solubility and effective hydrolysis rate constants, will vary with temperature and pH across different sites. The uncertainty resulting from the assumptions concerning environmental conditions results from a paucity of data describing conditions at waste management sites and from the requirement to conduct the assessment on a national basis.

V. B. 6. e. Some Uncertainties and Limitations of the Landfill Loading Term The most significant uncertainty in estimating landfill loading results from cumulative calculations. As shown in section V. B. 3, the landfill loading is calculated from a series of assumptions, each of which is highly variable ( e. g., the concentration of contaminants in the solvents). Other significant limitations include the following:

° Only compounds identified as the basis for listing F001 to F005 were considered in each analysis ( e. g., co contaminants such as metals and other compounds that could be present in solvents were not considered). Also, EPA did not consider other hazardous solvents due to the lack of data on their occurrence.

° The analysis only accounted for wipes generated by LQGs and small quantity generators ( SQGs), but negligible amounts of the constituent are present in the rest of the solid waste sent to the landfill. Therefore, it does not account for the potential introduction of the constituent by conditionally exempt small quantity generators ( CESQGs) and from household hazardous waste. 113 V. B. 6. f. Linearity of Models Most of the transport calculations are linear. For example, if landfill loading is doubled, then the groundwater concentration is also doubled. The risk loading thresholds presented in Table 15 assume such a linearity of the results. The indirect exposures, however, are not necessarily linear. This is because the indirect inhalation model is comprised of a series of modules and equations, with terms that rely on the differences in concentrations between different media. Risks for such indirect exposures were calculated assuming a uniform groundwater concentration of 1 mg/ L for each constituent ( EPA 1999). For simplicity, this risk screening assessment assumed that such results are linear ( e. g., a groundwater concentration of 2 mg/ L was assumed to result in twice the indirect exposure risk than a groundwater concentration of 1 mg/ L).

This assumption is expected to be appropriate for calculated groundwater concentrations near 1 mg/ L. However, as the receptor groundwater concentration becomes much less ( or much greater) than 1 mg/ L, there is expected to be greater uncertainty in the results. EPA did not evaluate the effect of this uncertainty on the results.

V. B. 7. What Are the Results of the Peer Review?

In September 1998, the risk analysis was sent to three experts outside of EPA. The peer review was limited to the fate of the constituents once the waste enters the landfill. The comments are detailed separately ( EPA, Summary and Assessment of Peer Review Comments Solvent Contaminated Towels, Rags, and Wipes, November 18, 1998) and summarized below. The reviewers identified ways in which the analysis is conservative, ways in which the analysis underpredicts risk, and uncertainties in the approach.

Ways in which the analysis was found to potentially over estimate risks include the following: ( 1) the model accounts for too little degradation of the solvent components in the landfill; ( 2) the assumption that none of the solvent is permanently bound to the wipe is conservative, as is the assumption that no degradation occurs after the compound leaves the landfill ( unfortunately, insufficient data is available in the literature to adequately quantify these effects); and ( 3) trichloroethylene's carcinogenic health effects may be overestimated.

Ways in which the analysis may underestimate risks include the following: ( 1) additional parameters other than climatic/ geographic conditions and landfill size could be relevant and should be considered in the sensitivity analysis ( a finding that other parameters are more sensitive than those parameters set at a high end would increase the modeled risk); ( 2) groundwater transport could result in larger risks than specified; ( 3) effects from co solubilization and co contaminants could increase risk; ( 4) the potential carcinogenic effects from one constituent, tetrachloroethylene, should have been considered; and ( 5) additional transport pathways exist and may result in higher risks than the pathways and risks evaluated. The latter includes evaluating a potentially more sensitive receptor ( worker at a landfill) and advective transport from the landfill resulting from the generation of methane. In addition, in considering degradation, the report ignores any effects from toxic daughter products, which would increase the risk to a receptor. 114 Other factors include those which have unknown effects on the risk assessment results. These include ( 1) misapplication of the landfill partitioning equations; ( 2) a need for greater and better presentation of uncertainty; ( 3) the lack of comparisons to actual or observed conditions which could support the conclusions of the report.

EPA did not modify the risk analysis to address peer reviewers' concerns but plans, instead, to address the peer review comments in conjunction with addressing public comments from the proposed rule. This approach was pursued in order to address all comments at one time before finalizing the proposal.

V. B. 8. Recommendations EPA today is proposing the following based on the findings of its risk screening analyses coupled with several policy decisions that address the uncertainties of these analyses:

° With respect to industrial wipes containing F listed solvents disposed directly in municipal landfills, EPA is proposing not to allow the following 11 F listed solvents in municipal landfills either because they pose unacceptable risks and/ or because those solvents are found in the Toxicity Characteristic ( TC) List ( See 40 CFR 261.24). These F listed solvents are pyridine ( TC), nitrobenzene ( TC), cresols ( TC), methyl ethyl ketone ( TC), tetrachoroethylene ( TC), chlorobenzene ( TC), 2 nitropropane, methylene chloride, benzene ( TC), carbon tetrachloride ( TC), and trichloroethylene ( TC). Of these 11 constituents ineligible for landfilling, 9 are toxicity characteristic ( TC) solvents. Of these 9 TC solvents, six ( 6) were not found to pose an adverse risk in the analysis. However, EPA is proposing that they be ineligible for landfilling because of their status as TC wastes.

° With respect to the remaining 19 F listed solvents, EPA is proposing to allow these solvents to be disposed of in municipal landfills provided they are " dry"; i. e., the wipes do not contain more than 5 grams per wipe solvent. This is in some cases more stringent than the results of our risk screening analysis. Because of the uncertainties and lack of detailed demographic data in the risk screening analysis, EPA has chosen to propose a more stringent condition in order to compensate for possible inaccuracies and to provide a simpler regulatory structure. However, the five gram standard for all contaminated wipes going to landfill should be achievable by many generators with little or no effort since they use very little solvent on each wipe as part of their production process. This proposed approach continues to provide regulatory relief and flexibility to generators, and has the benefit of providing a simple regulatory structure. In addition, the risk analysis shows the five gram standard to fall within the range of what is shown to be safe.

V. C. Ecological Risks Because constituents in these industrial wipes may impact ecological receptors differently 115 than human health receptors, a screening level analysis was conducted to assess potential ecological risks.

First, EPA identified appropriate ecological benchmarks. EPA developed freshwater benchmarks in preparation of the proposed 1999 Hazardous Waste Identification Rule ( 64 FR 63381, November 19, 1999). EPA also identified freshwater benchmarks in support of developing a protocol for permitting RCRA hazardous waste combustion facilities ( Screening Level Ecological Risk Assessment Protocol for Hazardous Waste Combustion Facilities, Peer Review Draft November, 1999). As a result, aquatic benchmarks were identified in this manner for 10 of the 30 constituents which form the basis for listing F001 to F005 wastes. These aquatic toxicity benchmarks are identified in Table 18. For convenience, Table 18 also identifies the underlying sources of the data identified in these two reports.

EPA conducted additional analyses to account for dilution of groundwater infiltration to a surface water body, using a conservative approach. First EPA identified a typical flow rate and dimensions of a small stream ( i. e., because higher contaminant concentrations would result from a small stream). Next, it identified the quantity of leachate generated from the modeled landfill and assumed that 100 percent of the contaminant leaving the landfill as leachate would enter the surface water.

Table 18 Aquatic Benchmarks for Constituents in Solvent Contaminated Industrial Wipes Constituent Name Concentration, mg/ L Source Acetone 1.5 ( 1); Suter and Tsao ( 1996)

Benzene 0.13 ( 2); Stephan et al. ( 1985); Suter and Tsao ( 1996) Table 18 Aquatic Benchmarks for Constituents in Solvent Contaminated Industrial Wipes Constituent Name Concentration, mg/ L Source 116 Carbon disulfide 0.00092 ( 2); Stephan et al. ( 1985); Suter and Tsao ( 1996)

Chlorobenzene 0.064 ( 2); Stephan et al. ( 1985); Suter and Tsao ( 1996)

Methylene chloride 2.2 ( 2); Stephan et al. ( 1985); Suter and Tsao ( 1996)

Nitrobenzene 0.27 ( 1); U. S. EPA ( 1987)

Tetrachloroethylene 0.098 ( 2); Stephan et al. ( 1985); Suter and Tsao ( 1996)

Toluene 0.0098 ( 2); Stephan et al. ( 1985); Suter and Tsao ( 1996)

1,1,1 Trichloroethane 0.011 ( 2); Stephan et al. ( 1985); Suter and Tsao ( 1996)

Trichloroethylene 0.047 ( 2); Stephan et al. ( 1985); Suter and Tsao ( 1996)

All other constituents No data   ( 1) U. S. Environmental Protection Agency. Screening Level Ecological Risk Assessment Protocol for Hazardous Waste Combustion Facilities, Peer Review Draft, November, 1999. Appendix E, Toxicity Reference Values, Screening Level Ecological Risk Assessment Protocol, August 1999. http:// www. epa. gov/ epaoswer/ hazwaste/ combust/ eco risk/ volume3/ appx e. pdf ( 2) U. S. Environmental Protection Agency. Data Collection for the Hazardous Waste Identification Rule. Section 14.0 Ecological Benchmarks. October 1999. http:// www. epa. gov/ epaoswer/ hazwaste/ id/ hwirwste/ pdf/ risk/ data/ s0044. pdf References cited in these two reports are as follows: Stephan, C. E., D. I. Mount, D. J. Hansen, J. H. Gentile, G. A. Chapman, and W. A. Brungs. 1985. Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses. PB85 227049. National Technical Information Service, Springfield, VA. Suter, II, G. W., and C. Tsao. 1996. Toxicological Benchmarks for Screening Potential Contaminants of Concern for Effects on Aquatic Biota: 1996 Revision. U. S. Environmental Protection Agency. Quality Criteria for Water   Update # 2. EPA 440/ 5 86 001. Office of Water Regulations and Standards. May 1987.

Assumptions regarding the typical size and flow rate of a small stream used in this analysis were taken directly from EPA's analysis for the paint production wastes proposed rule ( EPA, Risk Assessment Technical Background Document for the Paint and Coatings Hazardous Waste Listing Determination, January 2001) For modeling purposes, the stream is shaped as a rectangle 5.5 m wide, a width typical of a third order fishable stream ( van der Leeden et al., 1990). A third order stream refers to a type of stream segment classification. In this classification scheme, a first order stream segment is one with no tributaries. That is, a first order stream segment receives all of its flow from runoff from the surrounding watershed soils. A second order stream segment is produced when two first order stream segments come together. A third order stream segment occurs when two second order segments come together. The third order steam segment, therefore, has the combined flow of at least two second order stream segments. The third order stream was selected because it reasonably represents the smallest body of water that would routinely support recreational fishing of consumable fish. The stream segment modeled in this assessment is assumed to be homogeneously mixed with a depth of 0.21 m ( including water column and benthic sediment) 117 and a flow rate/ velocity of 0.5 m/ s ( van der Leeden et al., 1990). A stream with these dimensions, therefore, has a flow rate of 49,896 m3/ day.

The quantity of leachate generated from the modeled landfill is calculated from the landfill area and the infiltration rate. As discussed previously in this report, highest human health risks were found when using a landfill with an area of 8,094 m2 and an infiltration rate of 0.397 m/ year ( i. e., a small landfill in Houston Texas) ( EPA 1999). This is a total leachate generation rate of 9.2 m3/ day. The ratio of the stream flow to the landfill leachate flow is 5,400, assuming that the entire landfill leachate quantity enters the stream. This is much larger than the dilution attenuation factor of 27 used in the analysis for human health risks from drinking water wells and shows that much greater dilution results from a stream.

The benchmarks of Table 18 were compared to the simulated surface water concentration, calculated from the landfill loading rates identified for each constituent in Table 17 ( assuming no centrifuging). Results are presented in Table 19. Table 19 lists each constituent, its ecological benchmark ( from Table 18), and the simulated surface water concentration calculated assuming no pre centrifuging of solvent contaminated industrial wipes ( note that assuming centrifuging of the solvent contaminated industrial wipes prior to landfilling would result in even lower surface water concentrations). For each constituent, the simulated surface water concentrations are less than the corresponding ecological benchmark. Based on this analysis, EPA believes that none of these evaluated constituents would pose adverse ecological risks from the disposal of solventcontaminated industrial wipes in municipal solid waste landfills.

Table 19 Ecological Screening Results for Solvent Contaminated Industrial Wipes Constituent Name Concentration, mg/ L Conclusion Aquatic Benchmarka Surface Water, without pre Centrifugingb Acetone 1.5 0.02 No eco risk Table 19 Ecological Screening Results for Solvent Contaminated Industrial Wipes Constituent Name Concentration, mg/ L Conclusion Aquatic Benchmarka Surface Water, without pre Centrifugingb 118 Benzene 0.13 0.003 No eco risk Carbon disulfide 0.00092 0.0004 No eco risk Chlorobenzene 0.064 0.00003 No eco risk Methylene chloride 2.2 0.02 No eco risk Nitrobenzene 0.27 0.002 No eco risk Tetrachloroethylene 0.098 0.0001 No eco risk Toluene 0.0098 0.0004 No eco risk 1,1,1 Trichloroethane 0.011 0.0003 No eco risk Trichloroethylene 0.047 0.00002 No eco risk All other constituents No data   No data a Aquatic benchmarks are presented in Table 18. b Surface water concentrations calculated by combining EPA ( 1999) results with solvent loading and centrifuging assumptions described elsewhere for the human health risk assessment.

V. D. Assessing Risks from the Combustion of Disposables EPA's analysis of possible risks from the combustion of disposables in a municipal waste combustor addressed the following questions:

° Of the quantity of solvent entering the MWC, how much of it remains unburned in the residual ash?

° Would this residual quantity in the ash present a potential risk when disposed in a landfill? Would it meet numerical land disposal restrictions ( LDRs) and TC limits?

At the same time, the scope of the analysis was limited to potential risks from the ash only and did not address questions such as the following:

° Would there be any incremental risks from unburned constituents in stack emissions?

° Would the loadings contribute to dioxin/ furan formation or other undesirable effects? 119 The general approach to answering the above questions is as follows:

1. Estimate how much ( e. g., kg/ day) contaminant is sent to a MWC.

2. Estimate how much of each contaminant is destroyed ( or at least volatilized from the waste so it is not present in the ash). Also, estimate the size of a MWC and make assumptions regarding how many MWCs would send their ash to a single landfill.

3. Calculate how much contaminant remains in the ash. Compare these estimates to the risk loading thresholds calculated in section V. B. 1 to conclude if the quantity of residual solvent in the ash would be greater than or less than the quantity that may pose a risk. Also evaluate these levels against TC and LDR standards.

4. Identify what high end assumptions were used, as well as the uncertainties and limitations of the analysis.

5. Based on this information, make conclusions regarding the potential risks from combusting disposable industrial wipes.

As described below, the analysis uses several conservative assumptions. Therefore, the analysis can be characterized as a screening level analysis.

V. D. 1. What Quantities of Solvent Are Expected to be Sent to a MWC?

The first step of the analysis is to estimate the quantity of each constituent that is present in wipes sent to a MWC. Many of the same assumptions made in section V. B. for disposables in landfills are relevant to the MWC analysis as well. Discussed below are additional assumptions used to specifically apply to the MWC analysis.

There are 132 MWCs operating in the United States ( EPA 1997b). EPA used this number to obtain a nationwide average.

Due to the relatively small numbers of MWCs ( 132) and the relatively large number of landfills ( over 2,000), each of the MWC facilities would be expected to dispose of its ash in a different landfill. However, to apply an additional conservative factor, EPA assumed that there could be localized effects such that a large number of MWC units ( 5 times such a national average) use a single landfill.

EPA also assumed that a constituent would be destroyed to 0.01 percent of its initial loading. The basis for this assumption is presented in section V. D. 2. 120 Using these data and assumptions, EPA calculated the quantity of contaminant being sent to a individual MWC to be as follows:

1,009 million number of disposables used by LQGs and SQGs × 0.35 fraction with F listed constituents × [ 1 0.78] fraction combusting ( rather than landfilling) disposable industrial wipes × 0.1 or 0.5 fraction using given constituent × 0.1 to 0.51 fraction of constituent in solvent ( based on arithmetic average concentration) × [( 0.049 × fraction of disposables used by printers 25) + grams of solvent per wipe for a printer ( 0.951 × fraction of disposables used by non printers 12.5)] grams of solvent per wipe for a non printer × 5 localized concentration of generators above national average / 350 days per year that landfill operates / 132 number of MWCs nationwide x 0.0001 99.99% destruction 0.0003 to 0.003 kg/ day loading to landfill, depending on the containment V. D. 2. What Are the Properties of a Municipal Waste Combustion Unit?

Two properties of a MWC are important for these calculations: its size and its destruction efficiency. Size is used in estimating the quantity of ash generated. Destruction efficiency is used for identifying how much of the incoming solvent would be destroyed by the combustion process, and for estimating whether the resulting calculated concentrations of contaminants in the ash would exceed TC or LDR levels.

Estimating the Size of a MWC The data from EPA's Municipal Solid Waste Factbook ( 1997b) helped estimate the number and size of MWCs in the United States. It indicates that there are 132 MWCs with a total capacity of 111,149 tons per day, for an average capacity of 842 tons per day. To be conservative, this analysis assumes a small combustor ( the 10th percentile from the population of MWCs reported in the data) with a capacity of 72.3 tons per day ( 65,600 kg/ day). It assumes this combustor operates at 90 percent of capacity ( based on capacity utilization for MWCs as a whole). Thus, the total quantity of waste combusted by this small MWC is 59,000 kg trash per day ( 65,600 × 0.9).

The assumption of a small MWC unit is conservative because it generates a smaller quantity of ash in which any residual solvent is contained. In effect, a smaller quantity of ash will concentrate the solvent. For this analysis, a 75 percent weight reduction of the waste is assumed ( i. e., the quantity of ash generated is 25 percent of the feed, so 59,000 kg/ day x 0.25 = 15,000 kg/ day). Note that the size of the MWC unit, in this case, has no effect on the quantity of solvent present in wipes entering the unit. Even by assuming a smaller than average MWC, solventcontaminated industrial wipes would comprise a very small percentage of a unit's total feed. 23 As used here, destruction compares the composition of the exiting ash to the composition of the incoming municipal solid waste. For comparison, hazardous waste combustors require 99.99 percent destruction, when comparing the composition of the exiting air to the composition of the incoming waste. Because the constituents of concern are largely volatile, larger quantities of the unreacted constituent are expected to be present in exhaust gas rather than in ash residue.

121 Fate of Organics in a MWC A brief literature search was conducted to identify the fate of volatile constituents in MWCs. Most of the literature regarding organics focuses on dioxin, polychlorinated biphenyls ( PCBs), and similar compounds, which are of limited use in this analysis. However, three references were found to be relevant for estimating destruction of solvent constituents. These analyses indicate that the quantity of contaminant in stack air compared to the feed is at least 99.99 percent less, that there is even less contaminant in the ash, and organic contaminants that are present might be the result of formation from other non solvent materials rather than as unreacted raw MSW feed. Based on this information, EPA makes a conservative estimate that 99.99 percent of the incoming contaminant is destroyed with the remainder staying on the ash. 23 This is conservative for the following reasons:

° Destruction of trichlorofluoromethane is at least 99.998 percent in a MWC. The average destruction of trichlorofluoromethane ( CFC 11) was found to be 99.998 percent in a full scale municipal solid waste incinerator in Germany. This is based on the incineration of known amounts of solid polyurethane foam, which contain CFC 11. In this case, destruction is based on comparisons of exhaust gas composition to the feed. Similar ( slightly higher) destruction results were found at a test facility intended to simulate MWC conditions ( Rittemeyer et al., 1994). Ash concentrations were not measured. Similar investigations of other F001 through F005 solvent compounds were not located, but similar destruction equal to or greater than 99.99 percent were assumed for the remaining constituents based on the results for CFC 11.

° Any organics that are not destroyed will favorably partition to exhaust air rather than to ash. One source measured PCBs, chlorobenzenes, and chlorophenols ( as total levels of all of these components) at two full scale MWCs. At one facility, the quantities emitted in exhaust air ranged from 43 to 92 grams/ day, the quantity discharged in ash residue was 2 grams/ day, and the quantities in the feed ranged from 149 to 940 grams/ day. Similar trends were evident from the second facility ( Ozvacic et al., 1985). Similar partitioning ( at least 20: 1 gas to ash) is expected for the solvent compounds, since some are represented by these compound classes but most are even more volatile, which would decrease the quantity present in the ash compared to the exhaust air.

° Any organic compounds present in the ash or exhaust gas ( e. g., a limited subset of solvent compounds such as chlorobenzenes) may be the result of products of incomplete combustion, rather than uncombusted feed. In one test using a benchscale unit, MSW incinerator feed was spiked with a known amount of a 122 tetrachlorinated phenol isomer. Other chlorinated phenol isomers were present in the exhaust gas, but this particular isomer was present at much lower levels ( Kanters and Louw, 1994). Therefore, the presence of solvent components in ash or exhaust gas may be the result of their formation in the MWC, rather than as wholly unreacted MSW feed.

V. D. 3. What Are the Resulting Risk Estimates and LDR/ TC Results?

EPA used the results of sections V. D. 1 and V. D. 2 to estimate contaminant loadings to a MWC for the 30 F listed solvents. The findings are shown in Table 20 and are summarized as follows:

° TC limits. Nine of the 30 contaminants are TC constituents. These limits are expressed as milligram contaminant per liter of waste extract. The TC limits range from 0.5 mg/ L ( benzene) to 200 mg/ L ( methyl ethyl ketone). Based on the data in Table 20, the quantity of uncombusted solvent ranges from about 0.0003 to 0.003 kg/ day. With an ash generation rate of 15,000 kg/ day ( identified above), the concentration range of the solvent contaminants in the ash range from about 0.02 to 0.2 mg/ kg. The ash would not be expected to exhibit the TC for these constituents because even assuming that the entire quantity of solvent leaches from the ash would result in leachate concentrations well below their respective TC limits. ( As part of the calculations, 20 liters of extract are generated per kilogram of waste, based on the Toxicity Characteristic Leaching Procedure ( TCLP) protocol).

° LDR treatment standards. Of the 30 contaminants, all but three have numerical treatment standards. Most of these have limits based on total levels; LDR limits range from 2.6 to 170 mg/ kg. A few have limits based on TCLP levels; in these cases LDR limits range from 0.75 to 4.8 mg/ L. In each case the calculated concentrations in the ash ( 0.0003 to 0.003 mg/ kg) are well below these LDR levels.

° Risk loading thresholds. Risk loading thresholds, which identify the maximum quantity of solvent that can be disposed in a landfill and not present a risk, were identified in Table 15 for all 30 contaminants, based on a hazard quotient of 1 or cancer risk of 10 5 for a child receptor from multimedia exposure. The loading rate of contaminant in ash is less than the risk loading threshold for each constituent, indicating that none of the contaminants present a risk.

Table 20 Evaluation of Disposable Solvent Contaminated Industrial Wipes for MWC CAS No. Constituent ( RCRA Waste Codes) TC Limit, mg/ L LDR Limit Risk Loading Threshold ( kg/ d, per landfill) a Loading ( kg/ day, per landfill) Conclusion Table 20 Evaluation of Disposable Solvent Contaminated Industrial Wipes for MWC CAS No. Constituent ( RCRA Waste Codes) TC Limit, mg/ L LDR Limit Risk Loading Threshold ( kg/ d, per landfill) a Loading ( kg/ day, per landfill) Conclusion 123 67 64 1 Acetone ( F003) NAb 160 mg/ kg 1.73 0.0013 Acceptable 71 36 3 Butanol ( F003) NA 2.6 mg/ kg 1.61 0.0006 Acceptable 75 15 0 Carbon disulfide ( F005) NA 4.8 mg/ L TCLP 0.62 0.0003 Acceptable 108 90 7 Chlorobenzene ( F002) ( D021) 100 6 mg/ kg 0.36 0.0003 Acceptable 108 94 1 Cyclohexanone ( F003) NA CMBSTc 64.55 0.0006 Acceptable 1319 77 3 Cresols ( F004) ( D023) ( D024) ( D025) ( D026) 200 5.6 mg/ kg 0.41 0.0003 Acceptable 75 71 8 Dichlorodifluoromethane ( F001) NA NA 2.16 0.0003 Acceptable 95 50 1 1,2 Dichlorobenzene ( F002) NA 6 mg/ kg 12.84 0.0003 Acceptable 141 78 6 Ethyl acetate ( F003) NA 33 mg/ kg 16.17 0.0007 Acceptable 100 41 4 Ethyl benzene ( F003) NA 10 mg/ kg 11.95 0.0006 Acceptable 60 29 7 Ethyl ether ( F003) NA 160 mg/ kg 4.30 0.0003 Acceptable 110 80 5 2 Ethoxyethanol ( F005) NA NA 3.82 0.0003 Acceptable 78 83 1 Isobutyl alcohol ( F005) NA 170 mg/ kg 4.31 0.0006 Acceptable 67 56 1 Methanol ( F003) NA 0.75 mg/ L TCLP 5.90 0.0009 Acceptable 78 93 3 Methyl ethyl ketone ( F005) ( D035) 200 36 mg/ kg 0.32 0.0011 Acceptable 108 10 1 Methyl isobutyl ketone ( F003) NA 33 mg/ kg 0.03 0.0003 Acceptable 98 95 3 Nitrobenzene ( F004) 2 14 mg/ kg 0.043 0.0003 Acceptable 110 86 1 Pyridine ( F005) ( D038) 5 16 mg/ kg 0.006 0.0003 Acceptable 127 18 4 Tetrachloroethylene ( F002) ( D039) 0.7 6 mg/ kg 5.83 0.0013 Acceptable 108 88 3 Toluene ( F005) NA 10 mg/ kg 2.14 0.0015 Acceptable 71 55 6 1,1,1 Trichloroethane ( F002) NA 6 mg/ kg 15.81 0.0026 Acceptable Table 20 Evaluation of Disposable Solvent Contaminated Industrial Wipes for MWC CAS No. Constituent ( RCRA Waste Codes) TC Limit, mg/ L LDR Limit Risk Loading Threshold ( kg/ d, per landfill) a Loading ( kg/ day, per landfill) Conclusion 24 MWC ash is not required to meet LDR treatment standards. This evaluation was conducted for comparative purposes only.

124 76 13 1 1,1,2 Trichlorotrifluoroethane ( F002) NA 30 mg/ kg 403.37 0.0015 Acceptable 75 69 4 Trichlorofluoromethane ( F002) NA 30 mg/ kg 16.05 0.0010 Acceptable 1330 20 7 Xylenes ( total) ( F003) NA 30 mg/ kg 6.18 0.0006 Acceptable Carcinogens 71 43 2 Benzene ( F005) ( D018) 0.5 10 mg/ kg 0.24 0.0003 Acceptable 56 23 5 Carbon tetrachloride ( F001) ( D019) 0.5 6 mg/ kg 3.02 0.0003 Acceptable 75 09 2 Methylene chloride ( F002) NA 30 mg/ kg 0.39 0.0028 Acceptable 79 46 9 2 Nitropropane ( F005) NA 30 mg/ kg 0.0033 0.0003 Acceptable 79 01 6 Trichloroethylene ( F002) ( D040) 0.5 6 mg/ kg 27.66 0.0003 Acceptable 79 00 5 1,1,2 Trichloroethane ( F002) NA 6 mg/ kg 0.83 0.0003 Acceptable a Risk loading threshold shows disposal rate that results in an HQ= 1 or carcinogenic risk = 10 5. b NA = No applicable limit. c LDR limit of CMBST is technology based, requiring combustion as the treatment standard without a specific numeric limit. This requirement, in part, assumes a minimum 99.99% destruction for hazardous waste.

V. D. 4. Analysis of Results The results indicate that F listed constituents in MWC ash are expected to be destroyed in a MWC unit sufficient to meet existing LDR treatment standards and TC limits. 24 All of the 30 Flisted constituents would clearly be sufficiently destroyed such that any residual contaminant remaining in the ash would present negligible risk.

These conclusions are limited to the effects of the contaminants on the ash. Effects on stack air and subsequent risks, including risks from uncombusted solvents, as well as any products of incomplete combustion, were not evaluated. 25 As part of their petition, Kimberly Clark submitted data showing the evaporation rates of certain solvents from disposable industrial wipes. SAIC ( 1997) also presents data regarding evaporation rates under a variety of conditions.

125 V. D. 5. What High End Assumptions Are Related With this Risk Assessment?

This analysis uses many of the same high end assumptions used for the analysis for disposables in landfills presented in section V. B. The high end assumptions used in the MWC analysis, as they relate to the loading of the contaminant to the landfill, include the following:

° No removal processes are assumed to occur prior to combustion. This includes evaporation. 25 Removal efficiencies of such processes are variable.

° It is assumed that five MWCs use the same landfill. A similar ` localized concentration' effect was used for the landfill analysis ( equal to ten times the national average of landfills). While different multipliers were used for each analysis ( i. e., five for MWCs and ten for disposables in landfills), they have a slightly different meaning. Based on the data used for this analysis, there are 132 MWCs and over 2,000 landfills, or a national average of less than one MWC per landfill. By assuming as many as five MWCs use the same landfill, this is actually much greater than five times the national average.

Additionally, once the contaminant enters the landfill, a number of additional high end assumptions are associated with fate and transport. These include the following:

° The contaminants in the waste are assumed to be available for release and not irreversibly bound to the matrix.

° Use of one of four scenarios which results in the greatest receptor well concentrations ( i. e., a small landfill).

° The DAF for groundwater transport was evaluated at the 95th percentile level in a Monte Carlo analysis.

The contaminant loadings to a MWC were estimated as 0.0003 to 0.003 kg/ day, depending on the contaminant ( from Table 20). For comparison, the loadings to a landfill were estimated as 1.13 to 10.4 kg/ day, depending on the contaminant ( from Table 17).

V. D. 6. What Uncertainties and Limitations Are Related With this Risk Assessment?

This analysis assumes that a MWC would achieve 99.99 percent destruction of the organic constituents of concern. This assumption is based on the measured destruction of CFC 11 ( trichlorofluoromethane), one of the 30 F listed constituents, in a MWC. No data is available for the other constituents. The analysis also conservatively assumes that the unreacted solvent feed would partition to the ash when information from the literature indicates otherwise. Again, 126 however, the literature does not provide partitioning information for all of the F listed solvents.

EPA also did not assess whether certain compounds are actually formed during the combustion process as products of incomplete combustion. For example, dioxins and furans, as well as their precursors, are formed during the combustion process rather than present as incoming feed. However, there is no information to indicate what role, if any, these solvent constituents have on dioxin/ furan formation.

Additional uncertainties and limitations are similar or identical to those discussed for the landfill analysis in section V. B. These include the following:

° Only compounds identified as the basis for listing F001 to F005 were considered in each analysis ( e. g., co contaminants such as metals, and other compounds that could be present in solvents were not considered).

° Negligible amounts of the constituent are present in the rest of the solid waste sent to a MWC. Therefore, it does not account for the potential introduction of the constituent by CESQGs and from household hazardous waste.

V. D. 7. Was the Approach for MWCs Externally Reviewed?

The derivation of the risk loading thresholds for this analysis are identical to that used for the landfill analysis described in section V. B. The peer review evaluation results for this portion of the risk screening are applicable here. EPA also presented a draft of this analysis to the Integrated Waste Services Association ( IWSA).

IWSA stated that the analysis was extremely conservative and supported conclusions that generated ash would not pose risks for the majority of contaminants. However, they also stated that ash testing has not detected volatile organic compounds and that semivolatile organic compounds, when found, do not leach. Additionally, they supported an even greater destruction limit than 99.99 percent. The Association contends that the inclusion of these observations would support a conclusion that all solvent contaminated industrial wipes can be safely managed in a MWC.

EPA notes that this risk screening analysis did not identify any potential risks from solvents in residual ash. Even if the analysis was made less conservative, based on IWSA's concerns, the results of the analysis would not change.

V. D. 8 Recommendations For municipal waste combustion units that accept solvent contaminated industrial wipes, EPA is proposing to allow the generated municipal waste combustion ash to be disposed of in municipal waste landfills.

V. E. Assessing Risks from the Laundering of Reusable Industrial Wipes 127 SHOP AND PRINTER TOWEL GENERATORS Laundry Landfill Sludge Air Effluent wastewater ( sampled)

leaching/ ground water transport Figure 1: Fate of Solvent Components in Reusable Solvent Contaminated Wipes When Washed V. E. 1. How Can Solvents Enter the Environment from Reusable Industrial Wipes?

EPA proposed effluent guidelines for the industrial laundry industry ( 62 FR 66182, December 17, 1997). EPA subsequently finalized a decision not to promulgate effluent guidelines for this industry ( 64 FR 45071; August 18, 1999). For the proposed rule, EPA collected extensive information regarding the industrial laundry industry, types of items accepted, wastewater treatment technologies, and wastewater discharge characteristics. The data presented in this section highlights the findings of this work as it relates to risks from the laundering of wipes, as well as further investigations concerning potential risks from sludge.

Potential risks from laundering solvent contaminated industrial wipes result from the following operations ( see Figure 1):

° Storage. Oily materials are a potential source of fuel; in conjunction with sufficient air and heat a fire may result. Additionally, the presence of free liquids creates additional fuel and risk. To discourage free liquids in reusable wipes, the Uniform & Textile Service Association ( UTSA) has developed management guidelines encouraging generators to implement procedures to minimize free liquids and many states require that wipes sent to laundries not contain free liquids. Additionally, based on data collected in 1994 for the Agency's effluent guidelines rulemaking effort, most laundries at that time rejected articles with free liquids.

° Effluent. All industrial laundries discharge to a municipal treatment facility ( i. e., a publicly owned treatment works ( POTW)), which collects and further treats waste waters from industrial, commercial, and residential sources prior to discharge. Contaminants from industrial wipes, therefore, impact the environment following a complex path of pretreatment at the facility followed by centralized treatment at the POTW.

° Solid wastes. Industrial wipes, including solvent contaminated industrial wipes, 128 contribute a significant amount of contaminants to a laundry's pretreatment system. To control these pollutants prior to POTW discharge, laundries conduct treatment practices such as oil separation, dissolved air flotation, or conduct no treatment at all. The generated solids are managed as solid wastes using management methods such as landfilling or energy recovery.

° Air risks. Although the potential for air emissions is always present for volatile compounds, very little data regarding this pathway are available. The potential risks and loadings are greatest where the concentration of hydrocarbons are highest ( i. e., during wipe storage, and at oil removal points in the laundry's pretreatment system). As shown later in this section, industrial laundries should not meet the 25,000 kg per year threshold of a major source.

For this assessment, EPA only considered potential risks resulting from the disposal of industrial laundry sludge in a municipal solid waste landfill.

V. E. 2. What Quantity of Solvent Is Expected to be Present in Industrial Laundry Sludge?

Figure 1 shows a generalized diagram of how solvent components present in sludge from industrial laundries can impact human health and the environment. Multiple generators are assumed to generate industrial wipes and send these materials to an industrial laundry. Some of these wipes contain F001 to F005 solvents; the laundry cleans these ( and other) materials. When wipes are laundered, the contaminants present in the wipes are removed and transferred to air, water, or solid media. When the sludge is disposed, the contaminants in them can enter the landfill leachate and be transported to a receptor.

Risks from the landfilling of industrial laundry sludge are evaluated here using the following approach:

° The disposal of industrial laundry sludge was considered alone, without consideration of disposable industrial wipes in the same landfill ( i. e., additional sources of contaminants).

° Two different laundry sizes were used as calculation inputs to determine if sludge generated from such ` model' facilities would pose a risk when landfilled: an average and a large laundry. It was estimated that an average laundry would wash 270,000 pounds of printer wipes and 260,000 pounds of shop wipes per year while a few large laundries can wash up to 2,700,000 pounds of printer wipes and 2,600,000 pounds of shop wipes per year. Each size laundry was assumed to accept the same types of materials such that their washwater and sludge composition characteristics were the same.

Data characterizing laundry sludges from the washing of printer or shop wipes are not available for this analysis. As a result, the hazardous chemical sludge content was estimated from wastewater characterization. As with other analyses conducted in this report, EPA considered only the compounds that form the definition of the F001 through F005 solvent listing ( i. e., other non 129 listed solvents and co contaminants are not considered).

V. E. 2. a. Office of Water Data EPA's Office of Water ( OW) conducted sampling at numerous industrial laundries as part of effluent guidelines development for the 1997 proposed rule. The supporting record includes one sample of washwater generated from the washing of printer wipes from each of three different industrial laundries. This is washwater directly from the washer with no pretreatment or dilution. The highest detected concentration from the three samples was used in subsequent calculations. EPA does not consider this a high end parameter. EPA has noted the extreme variability of solvent use and therefore is not confident that its three data points for characterizing laundry washwater are representative. To account for this uncertainty, EPA selected the maximum concentration. Because sludge samples were not collected, an air/ water/ solid partitioning model ( WATER8) was used to estimate sludge loadings.

Only 11 of the 30 F list constituents were detected in one or more of these samples. The remaining constituents were either not detected or not analyzed, depending on the constituent. The 11 chemicals detected are presented in Table 21.

Table 21 Constituents Detected in OW Sampling The chemicals analyzed in the washwater samples were... The maximum concentration found in any one sample was ( mg/ L)... The average concentration of the three samples was ( mg/ L)... The results of the 1996 Printer Towel survey indicated...

Acetone 96.6 49.7 Used by 27% of printers Chlorobenzene 0.30 0.467 a   Ethylbenzene 29.24 13.2   Methylene chloride 1.54 0.614   Methyl ethyl ketone 2.24 3.09 a Used by 18% of printers Methyl isobutyl ketone 0.72 2.07 a   Tetrachloroethylene 6.16 3.92   Toluene 33.24 20.5 Used by 20% of printers 1,1,1 Trichloroethane 8.26 4.5   Trichloroethylene 0.328 0.476 a   Xylenes 102.7 35.9 Used by 20% of printers Remaining F list constituents Either not detected in any of the three samples, or were not analyzed.

a The average concentration is sometimes higher than the maximum concentration. This is because the detection 130 limit of non detect concentrations was used in calculating the average concentrations. The detection limits are sometimes greater than the detected values.

In calculations, EPA used the maximum concentrations as input to a partitioning model, WATER8. Using this model, only a portion of the solvent in the wastewater was assumed to partition to the sludge. Calculations were conducted with process assumptions that included the following:

° Volatility reduces due to surfactant. The result is that less chemical partitions to the air and more chemical partitions to water and sludge. The presence of a surfactant was suggested during the effluent guidelines public comment period as an assumption yielding a more realistic scenario.

° Wastewater treatment included commonly used oil/ water separation and settling. The analysis assumes that a less common technology, dissolved air flotation, is not present. This is a central tendency assumption because it is the most typical treatment used, and results in less solvent partitioning to the sludge than the DAF unit.

° Each pound of wipes washed is assumed to generate an average of 4.61 gallons of wastewater, with operations occurring an average of 350 days per year, based on analysis of the effluent guidelines data. These are central tendency.

As a result of using these assumptions, partitioning was found to range from 8 to 37 percent depending on the constituent. Detailed calculations of this partitioning are presented in ERG ( 2000).

The quantity of contaminant in the sludge is proportional ( and linear) to the quantity of wipes laundered. EPA assumed that the sludge is landfilled, such that the solvent contaminants could be released to the environment in the same manner as described in section V. B., for disposable industrial wipes. EPA also assumed that each laundry uses a different landfill for disposal. Therefore, EPA calculated the quantity of wipes that would be associated with sludge contaminant levels equal to the risk loading thresholds derived in section V. B. 1.

The overall approach is summarized below for an average sized laundry. For a large laundry, only the first two values change ( i. e., pounds printer wipes and pounds shop wipes washed per year):

270,000 pounds printer wipes washed per year by average laundry + ( 260,000 pounds shop wipes washed per year by average laundry × 0.5) accounts for lower quantity of solvent on shop wipes × 0.3 to 103 concentration of contaminant in washwater, mg/ L × 0.08 to 0.37 sludge partitioning without DAF ( constituent specific, derived using WATER8 model) × 4.61 gallons of water generated per pound of wipes washed 131 / 350 days per year that landfill operates 0.001 to 0.76 kg/ day loading to landfill, depending on the contaminant The results of these calculations are presented in section V. E. 3.

V. E. 2. b. Approach for Constituents Not Detected or Analyzed in OW Data The remaining 19 contaminants were either not analyzed by OW or were not detected at the sampled facilities. A different approach was necessary to estimate risk from sludge disposal for these solvents.

The 1996 printer survey ( referenced earlier) indicated that acetone, methyl ethyl ketone, toluene, and xylenes are the F listed solvents most often used by printers. Each of these constituents is present in significant concentrations using the OW data, as shown in Table 21. It is likely that the remaining solvents would be used less often, and would be present at lower concentrations in laundry washwater.

The remaining 19 solvents were assumed to have a washwater concentration equal to 2.2 mg/ L. This is the washwater concentration of methyl ethyl ketone ( MEK), a frequently used solvent by printers. Therefore, solvents used less frequently that MEK are assumed to have washwater concentrations no higher than MEK.

V. E. 3. Results EPA evaluated potential risks resulting from disposal of the laundry sludge alone, calculating the quantity of contaminant that would be present in the sludge from the treatment of reusable industrial wipes by ` average' sized industrial laundries. Results are presented in Table 22. As seen, only one solvent appears to pose a problem: 2 Nitropropane. 132 Table 22 Evaluation of Laundry Wastewater Treatment Sludges for Landfilling: Average Size Laundry Constituent Risk Loading Threshold ( kg/ d) Solvent quantity in sludge ( kg/ d) Conclusion Pyridine ( TC) 0.006 0.004 Acceptable Nitrobenzene ( TC) 0.04 0.005 Acceptable p Cresol ( TC) 0.41 0.004 Acceptable Acetone ( OW) 1.73 0.26 Acceptable Butanol 1.61 0.004 Acceptable Methyl isobutyl ketone ( OW) 0.03 0.002 Acceptable Isobutyl alcohol 4.31 0.004 Acceptable 2 Ethoxyethanol 3.82 0.006 Acceptable Ethyl ether 4.30 0.005 Acceptable Methanol 5.90 0.004 Acceptable Methyl ethyl ketone ( OW, TC) 0.32 0.006 Acceptable Ethyl acetate 16.17 0.004 Acceptable Carbon disulfide 0.62 0.008 Acceptable Tetrachloroethylene ( OW, TC) 5.83 0.03 Acceptable Chlorobenzene ( OW, TC) 0.36 0.0015 Acceptable Cyclohexanone 64.55 0.012 Acceptable Ethyl benzene ( OW) 11.95 0.21 Acceptable Toluene ( OW) 2.14 0.25 Acceptable Dichlorodifluoromethane 2.16 0.007 Acceptable 1,1,1 Trichloroethane ( OW) 15.81 0.03 Acceptable Trichlorofluoromethane 16.05 0.007 Acceptable 1,2 Dichlorobenzene 12.84 0.004 Acceptable Xylenes ( total) ( OW) 6.18 0.76 Acceptable 1,1,2 Trichlorotrifluoroethane 403 0.013 Acceptable 2 Nitropropane ©  air) 0.0033 0.004 Ineligible Methylene chloride ( C, OW) 0.39 0.005 Acceptable Benzene ( C, TC) 0.24 0.006 Acceptable 1,1,2 Trichloroethane ( C) 0.83 0.006 Acceptable Carbon tetrachloride ( C, TC) 3.02 0.007 Acceptable Trichloroethylene ( C, OW, TC) 27.66 0.001 Acceptable EPA also evaluated potential risks resulting from disposal of the laundry sludge when generated from a large laundry. These laundries have the same characteristics as described previously, with the exception that 2.7 million pounds of printer wipes and 2.6 million pounds of shop wipes are accepted annually by one laundry. Results are presented in Table 23. For this case, six solvents appear to pose a problem: acetone, nitrobenzene, 2 nitropropane, pyridine, toluene, and xylenes. 133 Table 23 Evaluation of Laundry Wastewater Treatment Sludges for Landfilling: Large Laundry Constituent Risk Loading Threshold ( kg/ d) Solvent quantity in sludge ( kg/ d) Conclusion Pyridine ( TC) 0.006 0.036 Ineligible Nitrobenzene ( TC) 0.04 0.049 Ineligible p Cresol ( TC) 0.41 0.036 Acceptable Acetone ( OW) 1.73 2.56 Ineligible Butanol 1.61 0.036 Acceptable Methyl isobutyl ketone ( OW) 0.03 0.020 Acceptable Isobutyl alcohol 4.31 0.036 Acceptable 2 Ethoxyethanol 3.82 0.058 Acceptable Ethyl ether 4.30 0.049 Acceptable Methanol 5.90 0.036 Acceptable Methyl ethyl ketone ( OW, TC) 0.32 0.063 Acceptable Ethyl acetate 16.17 0.040 Acceptable Carbon disulfide 0.62 0.080 Acceptable Tetrachloroethylene ( OW, TC) 5.83 0.30 Acceptable Chlorobenzene ( OW, TC) 0.36 0.015 Acceptable Cyclohexanone 64.55 0.13 Acceptable Ethyl benzene ( OW) 11.95 2.14 Acceptable Toluene ( OW) 2.14 2.48 Ineligible Dichlorodifluoromethane 2.16 0.071 Acceptable 1,1,1 Trichloroethane ( OW) 15.81 0.26 Acceptable Trichlorofluoromethane 16.05 0.071 Acceptable 1,2 Dichlorobenzene 12.84 0.036 Acceptable Xylenes ( total) ( OW) 6.18 7.57 Ineligible 1,1,2 Trichlorotrifluoroethane 403 0.13 Acceptable 2 Nitropropane ©  air) 0.0033 0.045 Ineligible Methylene chloride ( C, OW) 0.39 0.051 Acceptable Benzene ( C, TC) 0.24 0.062 Acceptable 1,1,2 Trichloroethane ( C) 0.83 0.058 Acceptable Carbon tetrachloride ( C, TC) 3.02 0.071 Acceptable Trichloroethylene ( C, OW, TC) 27.66 0.010 Acceptable V. E. 4. What High End Assumptions Are Related With this Analysis?

This analysis uses many of the same high end assumptions as used for the analysis for disposables in landfills presented in section V. B. The high end assumptions used in the laundry sludge analysis, as they relate to the loading of the contaminant to the landfill, include the following:

° In one case, EPA evaluated risks from sludge generated from a large laundry. While such facilities exist, they represent a small segment of the population. This is a highend parameter. However, results were presented for both a central tendency ( average sized) laundry and a large laundry. 134 Additionally, once the contaminant enters the landfill, a number of additional high end assumptions are associated with fate and transport. These include the following:

° The contaminants in the waste are assumed to be available for release, and not irreversibly bound to the matrix.

° Use of one of four scenarios which results in the greatest receptor well concentrations ( i. e., a small landfill).

° The DAF for groundwater transport was evaluated at the 95th percentile level in a Monte Carlo analysis.

V. E. 5 What Uncertainties and Limitations Are Related With this Analysis?

A primary area of uncertainty is sludge characterization. All evaluations were based on the projected levels of contaminant in the sludge, using OW data. There are further limitations associated with this approach.

° The analysis does not account for the range and variability of operations and sludge disposal practices at individual laundries. Such variability includes the following:

° Differences in pretreatment practices of incoming wipes or variability in use of the three OW wastewater samples.

° Variations in wastewater treatment system configurations and solvent removal efficiency. A more efficient system with a dissolved air flotation ( DAF) unit increases solvent loadings 2 to 3 times depending on the contaminant ( ERG, 2000). However, because DAF units are uncommon, results for such an analysis are not presented.

° EPA assumes that the only source of these constituents in the sludge results from the wipes and that there are no seasonal variations in wipe generation rates or in their composition.

° In this analysis EPA assumed that a single landfill is used in managing waste from a single facility. This is a nationwide average, but ignores regional variations where some states have higher concentrations of laundries. For example, nationwide there are about 2,500 landfills (` The State of Garbage in America,' BioCycle, April 1998) and about 1,000 laundries ( not all of the laundries necessarily manage shop and printer wipes) ( EPA, 2000). These data indicate that there are more landfills than laundries. However, the same sources indicate that in five states ( Connecticut, Delaware, Maine, Rhode Island, and Vermont), counted together, there are equal numbers of laundries and landfills ( 24).

° There is limited sampling data available, and only 11 constituents of interest were 26 The HAPs are benzene, carbon disulfide, carbon tetrachloride, chlorobenzene, cresols, ethyl benzene, methanol, methyl ethyl ketone, methylene chloride, methyl isobutyl ketone, nitrobenzene, 2 nitropropane, tetrachloroethylene, 1,1,2 trichloroethane, toluene, trichloroethylene, and xylenes.

135 detected. The remaining constituents were not available or not detected in the OW data set, however, the same series of assumption made for the constituents with OW data apply.

A second area of uncertainty is with the risk assessment itself. These uncertainties were identified in section V. B.

V. E. 6. Effects from Air Emissions EPA did not evaluate receptor risks from the management of solvent contaminated industrial wipes at industrial laundries. However, EPA did identify if industrial laundries are likely to be considered ` major sources' under the Clean Air Act ( CAA). One of the criteria for a major source is whether a single facility releases more than 25,000 kg ( 55,000 pounds) of CAA hazardous air pollutants ( HAPs) per year.

Since solvents are comprised of volatile compounds, the potential for air emissions will always exist. For the proposed effluent guidelines rule for industrial laundries, EPA estimated that, as a worst case scenario, HAPs would be emitted at a rate of 14,000 kg per year, per facility. As part of this present analysis regarding solvent contaminated industrial wipes, EPA has estimated quantities of solvent constituent releases into the air by modeling laundry facilities using the WATER8 computer model, as described in section V. E. 2.

Of the 30 constituents evaluated, 17 are HAPs. 26 The total quantity of the 17 HAPs released by a laundry with the assumptions described in this section is 500 kg per year, for a typical size laundry. For a large laundry, an estimated 5,000 kg of HAPs are estimated to be released annually. Based on this methodology, industrial laundry facilities would not be defined as a major source of pollution under the CAA since the total emissions of HAPs does not exceed the 25,000 kg ( 55,000 lbs.) per year threshold.

V. E. 7. Recommendations For industrial laundries accepting ` average' amounts of solvent contaminated shop and printer wipes, EPA is proposing to allow the generated industrial laundry sludge to be disposed of in municipal waste landfills. This recommendation would therefore allow 2 nitropropane contaminated sludges generated by industrial laundry wastewater treatment systems to be eligible for disposal, even though the results of Table 22 suggest it may present a risk. EPA is proposing this recommendation because it has been unable to identify in data searches even one generator who uses this chemical for cleaning or degreasing operations in conjunction with reusable ( or disposable) wipes.

With respect to the very few industrial laundries managing large amounts of solventcontaminated industrial wipes, EPA again is proposing to allow industrial laundry sludge to be 136 disposed of in municipal landfills. EPA is proposing this recommendation because it does not believe all generators are using F listed solvents, particularly those not found in the Office of Water's washwater samples. This analysis assumes that all washwaters contain the same constituents and concentrations as found in OW's samples, which is not possible. In addition, EPA has found from site visits that the very large industrial laundries tend to utilize solvent extraction technologies prior to entering the laundering process   thus the amount of contaminants in the sludge should be substantially reduced.

V. F. Damage Cases Associated with Solvent Contaminated Industrial Wipes EPA investigated whether there have been damage cases involving solvent contaminated industrial wipes ( e. g., where these wipes spontaneously combusted or fires occurred involving these materials). In support of this effort, EPA searched available databases and several other sources to determine if there are damage cases or any formal documentation available on the combustibility of solvent contaminated industrial wipes.

Based on engineering analyses and results from visits to generators, the most serious potential for environmental damage from solvent contaminated industrial wipes is the ignition of these material, although other forms of environmental damage are possible, such as uncontrolled land disposal resulting in groundwater contamination. While the migration of solvents in the groundwater has been well documented ( see, for example, EPA's 1980 background document for listing F001 through F005 wastes as hazardous), EPA expected it would be difficult, if not impossible, to try to investigate if contamination has resulted specifically from the landfill disposal of solvent contaminated media.

V. F. 1. What Are the Findings?

Although many fires caused by solvent contaminated industrial wipes are controlled and extinguished on site without assistance from emergency response personnel, other information collected found that sometimes the fires escalate and result in the entire facility being destroyed.

The U. S. Fire Administration ( USFA), within the Federal Emergency Management Agency ( FEMA), gathers and analyses information on the magnitude of the nation's fire problem, as well as detailed characteristics and trends. As part of this, participating local fire departments fill out Incident and Casualty reports as fires occur. These data are maintained on the National Fire Incident Reporting System ( NFIRS). Currently, 40 states and the District of Columbia voluntarily participate and report NFIRS data. Nearly 14,000 out of 30,000 fire departments report NFIRS data.

In an effort to understand the extent of reported fires at industrial laundries a query was made of NFIRS for the 1993 97 time period. Below is a summary of the number of the reported incidents, total number of states where incidents were reported, and estimated dollar loss. 27Discussion between Captain Rob Dunham, Deputy Fire Marshal, City of Oceanside, California and Jim O'Leary on August 27, 1999; discussion between Michael Perry, Division of Fire, City of Franklin, Ohio and Jim O'Leary on September 7, 1999.

137 Year Total Incidents No. States w/ Incidents Est. Dollar Loss( m) 1993 186 28 $ 2.1 1994 154 33 $ 1.2 1995 158 30 $ 1.7 1996 131 29 $ 1.1 1997 106 26 $ 3.3 The average number of reported fires was 147. However, maybe more important has been the steady decline from a high in 1993 of 186 reported fires to 106 in 1997. Assuming only one fire occurred per facility, this represents six percent of the universe of industrial laundries. Similarly, the average estimated dollar loss of most reported fires ranges from a low of $ 7,792 in 1994 to $ 31,132 in 1997. A closer look at the data reveals that most reported fires are at the lower dollar loss range, but that a few fires with million dollar ( and higher) estimated losses skew the results higher. Also, in discussions and correspondence with a few fire marshals where high dollar losses occurred, wipes were involved in the cause   primarily through the self combustion of these materials. 27 As discussed in the preamble to this rule, officials from the industrial laundry trade associations are very concerned about spontaneous combustion. EPA has asked for comments regarding whether generators should be allowed to use exotic solvents in conjunction with industrial wipes to send their wipes off site with free liquids to avoid the potential of self ignited fires.

EPA also searched other available databases and the Internet, and requested information from several State agency officials and representatives from trade associations. Evidence of damage as a result of spontaneous combustion ( or self ignition) of wipes was found. Several experts contacted noted the danger of ignition of solvent contaminated industrial wipes. However, given the small scale of most fires associated with these materials, documentation of specific instances of fire damage due primarily to spontaneous combustion of solvent contaminated industrial wipes was not available. Additional information on fires caused by these materials may exist in local fire departments not contacted by EPA.

According to interviews with representatives from the insurance industry and states, solvent contaminated industrial wipes do present a fire risk. However, most of the fires resulting from solvent contaminated industrial wipes are small in scale, are easily extinguished with a fire extinguisher, and cause minimal damage. Most of the fires can be easily avoided through better management. One insurance industry representative suggested that fires may be more frequent in industrial laundries since they accept wipes from many different companies and may not be able to control the mixing of combustibles. 138 V. F. 2. Sources for Information on Environmental Damage from Solvent Contaminated Industrial Wipes EPA reviewed data from numerous sources to identify evidence of environmental damage from solvent contaminated industrial wipes. These sources included publicly available databases, conversations with officials in States and EPA Regions, fire related trade associations, the Internet, local fire departments, and background materials in OW's docket supporting the pretreatment standards rule for industrial laundries. Each of these sources is discussed below.

Databases Numerous databases catalogue accident and damage information. The Right to Know Network ( http:// www. rtk. net) contains several on line databases which can be searched. The following RTK Net databases were investigated for information regarding damage cases involving solvent contaminated industrial wipes using related search terms ( e. g., industrial laundry, solvent, rags, wipes, F001 F005). The following lists the specific databases that were searched, what was looked for, and what relevant information was found, if any.

ARIP ( Accidental Release Information Program) ARIP contains information on the causes of accidents, and particularly targets accidents that resulted in off site consequence or environmental damage.

CERCLIS ( CERCLA " Superfund" Information System) The database contains information on hazardous waste sites, site inspections, preliminary assessments, and remedial status.

DOCKET This database contains EPA Civil Court cases and Administrative Actions filed by the Department of Justice on behalf of EPA.

ERNS ( Emergency Response Notification System)   ERNS compiles reports of nonroutine releases of certain substances when those releases exceed a reportable quantity ( RQ). This database can be searched by geographical area, discharger, and material.

FINDS ( Facility Index System)   This database provides basic information on facilities regulated under a variety of EPA program areas.

PCS ( Permit Control System for water permits)   This database tracks NPDES surface water permits issued under the Clean Water Act.

RCRIS ( RCRA Information System)   This database contains information regarding violations, enforcement actions, and inspections at RCRA facilities.

NFIRS ( National Fire Incident Reporting System)   This database compiles information about fires through reports filed to the U. S. Fire Administration from local fire departments. 139 BLS ( Bureau of Labor Statistics)   The Bureau of Labor Statistics Internet site contains a database ( http:// www. osha. gov/ oshstats/ bls) containing information on laundry, cleaning, and garment services.

OSHA ( Occupational Safety and Health information)   OSHA's Office of Statistics was contacted to search their databases.

States Few state officials provided any information or comments on damage cases caused by solvent contaminated industrial wipes. Information regarding damage cases from both generators and industrial laundries was generally not available as many states and EPA RCRA enforcement officials do not extensively regulate or collect information on many of these facilities. 140 VI. References ERG. 2000. Mass Balance Estimation for Solvents on Soiled Printer Towels   Analysis Based on Office of Water Printer Towel Sampling Data. February 1, 2000.

Jacqueline Kanters and Robert Louw. " Chlorine Input and Output in Combustion of Municipal Solid Waste in a Lab Scale Mini Reactor System." Chemosphere 29( 9 11), pp 1919 1925 ( 1994).

V. Ozvacic, G. Wong, H. Tosine, R. E. Clement, J. Osburne. " Emissions of Chlorinated Organics from Two Municipal Incinerators in Ontario." Journal of the Air Pollution Control Association 35( 8), pp 849 855 ( 1985).

C. Rittemeyer, P. Kaese, J. Vehlow, W. Vilöhr. " Decomposition of Organohalogen Compounds in Municipal Solid Waste Incineration Plants. Part II: Co Combustion of CFC Containing Polyurethane Foams." Chemosphere 28( 8), pp 1455 1465 ( 1994).

SAIC. " Use and Management Practices of Solvent Contaminated Industrial Shop Towels," Final Report. December 1997.

SGIA. 1998a. Memorandum from Marcia Kinter ( Screenprinting and Graphic Imaging Association International) to Jim O'Leary ( EPA). February 20, 1998 SGIA. 1998b. Memorandum from Marcia Kinter ( Screenprinting and Graphic Imaging Association International) to Jim O'Leary ( EPA). May 4, 1998.

` The State of Garbage in America,' BioCycle. April 1998.

U. S. Environmental Protection Agency. Final Best Demonstrated Available Technology ( BDAT) Background Document for Universal Standards, Volume A. July 1994 U. S. Environmental Protection Agency. Exposure Factors Handbook. August 1997a. Final Report. EPA/ 600/ P 95/ 002Fa.

U. S. Environmental Protection Agency. Technical Development Document for Proposed Pretreatment Standards for Existing and New Sources for the Industrial Laundries Point Source Category. EPA 821 R 97 007. November 1997b.

U. S. Environmental Protection Agency. Municipal Solid Waste Factbook  Internet Version. November 1997c. < http:// www. epa. gov/ epaoswer/ non hw/ muncpl/ factbook/>

U. S. Environmental Protection Agency. Summary and Assessment of Peer Review Comments Solvent Contaminated Towels, Rags, and Wipes. November 18, 1998.

U. S. Environmental Protection Agency. Estimating the Risk from the Disposal of Solvent Contaminated Shop Towels and Wipes in Municipal Landfills." March 1999. 141 U. S. Environmental Protection Agency. Technical Development Document for the Final Action Regarding Pretreatment Standards for the Industrial Laundries Point Source Category. EPA 821 R 00 006. March 2000.

van der Leeden, F., F. L. Troise, and D. K. Todd. 1990. The Water Encyclopedia. 2nd edition. Chelsea, Michigan: Lewis Publishers.