OFFICE OF PREVENTION, PESTICIDES, AND TOXIC SUBSTANCES UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D. C. 20460 TXR No: 0050429 30 Jan 2002 Memorandum SUBJECT: LINURON (PC Code: 035506) REVISED Toxicology Disciplinary Chapter for the Reregistration Eligibility Decision Document, (Replaces TXR No. 0050415)

FROM: Robert Fricke, Ph. D. Reregistration Branch 2 Health Effects Division (7509C)

THRU: Alan Nielsen, Branch Senior Scientist Reregistration Branch 2 Health Effects Division (7509C)

TO: Carol Christensen, Risk Assessor Reregistration Branch 2 Health Effects Division (7509C)

DP Barcodes: D272367 Submission: S590997 Action Requested: Review toxicology studies submitted by the registrant and prepare the toxicology chapter to support reregistration eligibility decision for linuron Attached is the updated toxicology chapter summarizing the findings of the toxicology studies. LINURON PC Code: 035506 REVISED (Replaces Previous Document TXR No. 0050415)

Toxicology Disciplinary Chapter for the Reregistration Eligibility Decision (or Registration Support) Document Date completed: January 30, 2002 Prepared by: Robert F. Fricke, Ph. D Reregistration Branch 2 Health Effects Division Mail Code 7509C Peer reviewed by: Yung Yang, Ph. D. Reregistration Branch 2 Health Effects Division Mail Code 7509C Robert F. Fricke, Toxicologist Yung Yang, Toxicologist TABLE OF CONTENTS 1 HAZARD CHARACTERIZATION ........................................... 5 2 REQUIREMENTS ........................................................ 6 3 DATA GAPS ............................................................ 7 4 HAZARD ASSESSMENT.................................................. 7 4. 1 Acute Toxicity ....................................................... 7 4. 2 Subchronic Toxicity................................................... 8 4.2.1 870.3100 90 Day Oral Toxicity  Rat .............................. 8 4.2.2 870.3150 90 Day Oral Toxicity  Dog .............................. 8 4.2.3 870.3200 21/ 28 Day Dermal Toxicity  Rabbit ....................... 8 4.2.4 870.3250 90 Day Dermal Toxicity ................................ 8 4.2.5 870.4365 90 Day Inhalation Toxicity .............................. 9 4. 3 Prenatal Developmental Toxicity ........................................ 9 4.3.1 870.3700a Prenatal Developmental Toxicity Study  Rat ................ 9 4.3.2 870.3700b Prenatal Developmental Toxicity Study  Rabbit ............ 10 4.4 Reproductive Toxicity ................................................ 11 4.4.1 870.3800 Three Generation Reproduction and Fertility Effects  Rat .... 11 4.4.2 870.3800 Two Generation Reproduction Study in the Rat ............. 13 4. 5 Chronic Toxicity .................................................... 15 4.5.1 870.4300 Combined Chronic Toxicity/ Carcinogenicity Study CD( SD) BR Rats ............................................... 15 4.5.2 870.4100b Chronic Toxicity  Dog ................................ 17 4.5.3 870.4100b Chronic Toxicity  Dog ................................ 18 4.6 Carcinogenicity ..................................................... 19 4.6.1 870.4200b Carcinogenicity Study  Crl: CD 1 (ICR) BR Mouse ......... 19 4.6.2 870.4300 Carcinogenicity Study CD( SD) BR Rats ................... 20 4. 7 Mutagenicity ....................................................... 20 4. 8 Neurotoxicity....................................................... 22 4.8.1 870.6100 Delayed Neurotoxicity Study  Hen ....................... 22 4.8.2 870.6200a Acute Neurotoxicity Screening Battery .................... 22 4.8.3 870.6200b Subchronic Neurotoxicity Screening Battery ............... 22 4.8.4 870.6300 Developmental Neurotoxicity Study ...................... 22 4. 9 Metabolism ........................................................ 22 4.9.1 870.7485 Metabolism  Rat ..................................... 22 4.9.2 870.7600 Dermal Absorption  Rat ............................... 23 4.10 Special Studies ...................................................... 23 4.10.1 Biochemical and Histopathological Effects in Rats ................... 23 4.10.2 Leydig Cell Tumorigenisis in Rat ................................. 25 4.10.3 Special Reproduction Study  Cross mating  Rat ..................... 27 5 TOXICITY ENDPOINT SELECTION ....................................... 28 5.1 See Section 9.2 for Endpoint Selection Table .............................. 28 5. 2 Dermal Absorption ................................................... 28 5.3 Classification of Carcinogenic Potential .................................. 28 5.3.1 Conclusions .................................................. 28 5.3.2 Classification of Carcinogenic Potential ............................ 28 5.3.3 Quantification of Carcinogenic Potential ........................... 28 6 FQPA CONSIDERATIONS................................................ 28 6.1 Special Sensitivity to Infants and Children ................................ 28 6. 2 Recommendation for a Developmental Neurotoxicity Study .................. 29 7 OTHER ISSUES......................................................... 29 8 REFERENCES .......................................................... 29 9 APPENDICES ......................................................... 33 9. 1 Toxicity Profile Summary Tables ....................................... 34 9.1.1 Acute Toxicity Table ........................................... 34 9.1.2 Subchronic, Chronic, and Other Toxicity Table ...................... 34 9.2 Summary of Toxicological Dose and Endpoints for Linuron for Use in Human Risk Assessment......................................................... 41 5 1 HAZARD CHARACTERIZATION The toxicological database for linuron is adequate to assess the potential hazard to humans, including special sensitivity of infants and children. The database will support the reregistration eligibility decision (RED) for the current registered uses. However, the Health Effects Division's Hazard Identification Assessment Review Committee (HIARC) determined that a developmental neurotoxicity study and a 28 day inhalation study are required to provide better hazard characterization..

Linuron has low acute toxicity by the oral (LD50 = 2600 mg/ kg), dermal (LD50 > 2000 mg/ kg), and inhalation (LC50 > 218 mg/ L) routes of exposure. Linuron is not an eye or skin irritant, and not a skin sensitizer.

Chronic toxicity studies in the dog, rat and mouse showed altered hematological findings. Beagle dogs fed linuron at dietary concentration of 625 ppm, resulted in hemolytic anemia and secondary erythropogenic activity evidenced by slightly reduced hemoglobin, hematocrit, and erythrocyte counts accompanied by hemosiderin deposition in liver Kupffer cells and erythroid hyperplasia of bone marrow. In the rat study, linuron, at a dietary dose 125 ppm (5.1 mg/ kg/ day in males and 7.8 mg/ kg/ day in females) caused an increase in the incidence of hemolysis. Microscopic observations revealed increased incidence of hemosiderin in Kupffer cells and increased hemosiderosis in bone marrow, spleen, and/ or mesenteric lymph nodes). Rats also showed decreased body weight gains in both sexes and increased incidences of microscopic changes in the epididymides (perivasculitis/ vasculitis) and renal pelvis (transitional cell hyperplasia and mineralization/ calculi) of males and in the kidneys (calculi in renal tubules) of females. Systemic toxicity observed in mice included increased methemoglobin formation and vacuolation and hemosiderosis of the spleen.

Oncogenicity studies in the rat and mouse did not show consistent tumor profiles between sexes and species. In the combined chronic toxicity/ oncogenicity study in rats, common neoplasms, included pituitary adenomas of the pars anterior in both male and female rats and mammary fibroadenomas in female rats. Testicular adenomas were observed in 6, 28 and 54%, respectively for control, 125 and 625 ppm dose groups. Decreased incidences of both these tumor types were noted in the high dose female group. In the mouse oncogenicity study, treatment of up to 104 weeks with 1500 ppm resulted in a significant increase in the incidence of hepatocellular adenomas (control, 6%; 1500 ppm, 25%, p < 0.05) in females. Linuron was not mutagenic in bacteria or in cultured mammalian cells. There was also no indication of a clastogenic effect up to toxic doses in vivo. Based on the results of these studies, linuron was classified as an unquantifiable Group C carcinogen (a possible human carcinogen for which there is limited animal evidence) requiring no quantification of human cancer risk..

There is no qualitative/ quantitative evidence of increased susceptibility of rabbit developmental study; developmental effects were seen at a dose higher than that causing maternal toxicity. In the rat developmental study, increases in post implantation losses and increases in fetal resorptions/ litter were seen as a dose that caused decreases in maternal body weight and food consumption. The HIARC determined that the developmental effects are not indicative of qualitative evidence of susceptibility, since increases in resorptions were marginal and there was no change in the number of live fetuses to corroborate the increases in post implantation losses. 6 There was no quantitative evidence of susceptibility either in the 2 generation or the 3 generation reproduction studies. In the 2 generation study, reduced body weight gains of pups were seen at the same dose that caused decreases in parental body weights. In the 3 generation study, offspring effects (deceased pup survival and pup body weight) were seen a dose ( 44 mg/ kg/ day) higher than the dose that caused decreases in body weight gain in the parental animals (9 mg/ kg/ day).

However, when the reproductive effects were examined, testicular atrophy was seen at the same dose (625 ppm, 45 mg/ kg/ day) in both studies. While the F0 males were not affected, testicular lesions and reduced fertility were seen in the F1 males. This effect in the F1 males is an indication of qualitative evidence of susceptibility.

In a metabolism study linuron (single doses at 24 mg/ kg and 400 mg/ kg) was administered by gavage to male and female rats. The biological half lives ranged from 21 hr in the low dose males to 56 hr in the high dose females. Total recovery of radioactivity was 96% in males and 97% in females, the majority of the administered 14 C linuron was eliminated in the urine (> 80%) and, to a lesser extent, in the feces (~ 15%). Tissue and organ residues were very low (< l%) at both dose levels, and there was no indication of accumulation or retention of linuron or its metabolites. The major metabolites identified in the urine were hydroxy norlinuron, desmethoxy linuron and norlinuron, and in feces, hydroxy norlinuron, and norlinuron. Neither hydroxy 3,4 dichloroanaline nor 3,4 dichloroanaline were present in any of the samples. Exposure to linuron appeared to induce mixed function oxidative enzymes.

There is ample evidence from special studies submitted by the registrant as well as open literature studies which indicate that linuron is an endocrine disruptor. These findings include, in part: (1) competitive androgen receptor antagonist; but not an estrogen receptor antagonist; (2) competitive inhibition of the transcriptional activity of dihydrotestosterone (DHT) human androgen receptor (hAR) in vitro, decreased anogenital distance and/ or an increase in the retention of areolae/ nipples in male offspring following in utero exposure to linuron; (3) inhibition of steroidogenic enzymes, and (4) decreased responsiveness of Leydig cells to luteinizing hormone in both immature (22 days) and mature (11 months) male rats treated with linuron, mature rats were less responsive that immature ones; (5) F0 and F1 males had significantly increased levels of estradiol and luteinizing hormone.

2 REQUIREMENTS The requirements (CFR §158.340, revised as of July 1, 1999) for Food and Non Food Use for linuron are summarized in Table 1. Use of the new guideline numbers does not imply that the new (1998) guideline protocols were used. 7 Test Technical Required Satisfied 870.1100 Acute Oral Toxicity ......................... 870.1200 Acute Dermal Toxicity ....................... 870.1300 Acute Inhalation Toxicity .................... 870.2400 Primary Eye Irritation ....................... 870.2500 Primary Dermal Irritation ..................... 870.2600 Dermal Sensitization ........................ Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 870.3100 Oral Subchronic (Rodent) .................... 870.3150 Oral Subchronic (Non Rodent) ................ 870.3200 21 Day Dermal ............................. 870.3250 90 Day Dermal ............................. 870.3465 28 Day inhalation 870.3465 90 Day Inhalation .......................... Yes Yes No No Yes No Yes a Yes a

No 870.3700a Developmental Toxicity (Rodent) .............. 870.3700b Developmental Toxicity( Non rodent) ........... 870.3800 Reproduction .............................. Yes Yes Yes Yes Yes Yes 870.4100a Chronic Toxicity (Rodent) ..................... 870.4100b Chronic Toxicity (Non rodent) ................. 870.4200a Oncogenicity (Rat) ........................... 870.4200b Oncogenicity (Mouse) ........................ 870.4300 Chronic/ Oncogenicity ........................ Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 870.5100 Mutagenicity— Gene Mutation  bacterial ......... 870.5300 Mutagenicity— Gene Mutation  mammalian ...... 870.5385 Mutagenicity— Mammalian bone marrow chromosomal aberration test ................... 870.5395 Mutagenicity— in vivo mammalian cytogenetics 870.5550 Mutagenicity— USD in Mammalian cells in vitro ... Yes Yes Yes No Yes Yes Yes Yes Yes 870.6100a Acute Delayed Neurotox. (Hen) ................ 870.6100b 90 Day Neurotoxicity (Hen) ................... 870.6200a Acute Neurotox. Screening Battery (Rat) ......... 870.6200b 90 Day Neuro. Screening Battery (Rat) ........... 870.6300 Developmental Neurotoxicity .................. No No No No Yes

No 870.7485 General Metabolism .......................... 870.7600 Dermal Penetration .......................... Yes No Yes Yes a These data requirements are satisfied by the corresponding chronic studies 3 DATA GAPS 28 Day inhalation study (OPPTS 870.3465) Developmental neurotoxicity study (OPPTS 870.6300)

4 HAZARD ASSESSMENT 4.1 Acute Toxicity Adequacy of data base for acute toxicity: Linuron has low acute toxicity, with toxicity 8 categories of III for oral (LD50 = 2600 mg/ kg), dermal (LD50 > 2000 mg/ kg) and toxicity category IV for inhalation ( LC50 > 218 mg/ L). Primary eye and skin irritation studies were category III and IV, respectively; no dermal sensitization was observed in guinea pigs. The acute toxicity data for linuron are summarized below in Table 2.

Table 2: Acute Toxicity of Linuron, Technical Guideline No. Study Type MRID No. Results Toxicity Category 870.1100 Acute Oral (Rat) 00027625 LD50 = 2600 mg/ kg III 870.1200 Acute Dermal (Rabbit) 00027625 LD50> 2000 mg/ kg III 870.1300 Acute Inhalation (Rat) 00053769 LC50 > 218 mg/ L IV 870.2400 Primary Eye Irritation 42849001 Slight conjunctival redness at 24 hrs; clear at 72 hrs III 870.2500 Primary Skin Irritation 42849002 Not an irritant IV 870.2600 Dermal Sensitization 00146868 Not a sensitizer N/ A 4.2 Subchronic Toxicity Adequacy of data base for subchronic toxicity: No subchronic toxicity studies were available; the respective chronic toxicity studies satisfies the data requirements. A 28 day inhalation study is required at this time to address the concern for inhalation exposure.

4.2.1 870.3100 90 Day Oral Toxicity  Rat The chronic rat study presented later in section 4.5.1 (870.4100a) satisfies the data requirements for 870.3100.

4.2.2 870.3150 90 Day Oral Toxicity  Dog The chronic dog study presented later in section 4.5.2 (870.4100b) satisfies the data requirements for 870.3150.

4.2.3 870.3200 21/ 28 Day Dermal Toxicity  Rabbit No study available 4.2.4 870.3250 90 Day Dermal Toxicity No study available 4.2.5 870.4365 90 Day Inhalation Toxicity 9 No study available. A 28 day inhalation study has been identified as a data gap by the HIARC.

4.3 Prenatal Developmental Toxicity Adequacy of data base for Prenatal Developmental Toxicity: The data base for prenatal developmental toxicity is considered complete and no additional studies are required at this time. There is no qualitative/ quantitative evidence of increased susceptibility observed in the rat and rabbit developmental toxicity studies 4.3.1 870.3700a Prenatal Developmental Toxicity Study  Rat Executive Summary: In a developmental toxicity study (MRID No: 00018167), 27 presumed pregnant Crl: CD rats per group were administered 0, 50, 125, or 625 ppm of linuron (97% a. i.; Lot No. INZ 326 118) in the diet on gestation days (GD) 6 15, inclusive. Average doses to the treated dams were 5.0, 12, and 50 mg/ kg/ day, respectively. The day evidence of mating was found was designated GD 1. Maternal body weights and food consumption were recorded on GD 6, 10, 16, and 21. On GD 21, all surviving dams were sacrificed and all fetuses were weighed and examined for external malformations/ variations. Crown rump length was measured on each fetus. Approximately one half of the fetuses in each litter were fixed in Bouin's solution for visceral examination and the remaining one half were processed for skeletal examination.

All animals survived to scheduled termination without the appearance of any treatmentrelated clinical signs of toxicity. Gross necropsy was unremarkable. No treatmentrelated clinical signs of toxicity were observed. Body weight gains and food consumption by the low and mid dose groups were similar to the controls throughout the study. Body weights of the high dose group were significantly (p # 0.05) less than the control group on GD 10, 16, and 21. Food consumption by the high dose group was significantly (p # 0.05) less than that of the controls for the intervals of GD 6 10 and 10 16.

The maternal toxicity LOAEL is 625 ppm (50 mg/ kg/ day) based on reduced body weight gain and food consumption. The maternal toxicity NOAEL is 125 ppm (12 mg/ kg/ day).

No dose or treatment related effects were observed on fetal sex ratios, numbers of corpora lutea/ dam, implantations/ dam, live or dead fetuses/ dam, fetal body weights, or crown rump length. In the control, low, mid, and high dose groups post implantation loss was 5.8, 3.5, 4.4, and 14.0%, respectively, and the number of resorptions per litter with resorption was 1.6, 1.6, 1.2, and 2.1, respectively.

No treatment related external or visceral malformations/ variations were noted. In the high dose group bipartite thoracic vetebral centra was observed in 7 fetuses from 7 litters and unapposed sternebrae were observed in 3 fetuses from 3 litters. These anomalies were not found in the control group and were considered indicative of developmental delays. 10 The developmental toxicity LOAEL is 625 ppm (50 mg/ kg/ day) based on increases in post implantation loss and in litter/ fetal resorptions. The developmental toxicity NOAEL is 125 ppm (12 mg/ kg/ day).

This study is classified as Acceptable/ Guideline and does satisfy the guidelines for a developmental toxicity study [OPPTS 870.3700 (83 3a)] in rats. Deficiencies included no information on dietary formulation preparation or analyses, the treatment period should have been GD 7 16, body weight on GD 0 were not collected, fetal anomalies were not classified as malformations or variations, and fetuses were not individually identified. These deficiencies were considered to be minor.

4.3.2 870.3700b Prenatal Developmental Toxicity Study  Rabbit Executive Summary: In a developmental toxicity study (MRID Nos: 00153867 and 40437201), 25 presumed pregnant New Zealand white rabbits per group were administered 0, 5, 25, or 100 mg/ kg/ day of linuron (96.2% a. i.) by gavage on gestation days (GD) 7 19, inclusive. Doses were chosen based on the results of a range finding study. The vehicle was 0.5% hydroxypropyl methylcellulose. On GD 29, all surviving does were sacrificed and the livers weighed. All fetuses were weighed and examined for external and visceral malformations/ variations including free hand sectioning of the brain. All fetuses were eviscerated and processed for skeletal examination.

No dose or treatment related clinical signs of toxicity, maternal deaths, or necropsy findings were observed in any group. Absolute body weights and food consumption for the low and mid dose groups and body weight gain by the low dose group were not affected by treatment.

Body weight of the high dose group was significantly (p # 0.05) less than that of the controls on GD 19. Body weight gains during GD 13 16 were slightly less for the middose group (50%, n. s.) and significantly less for the high dose group ( 0.01 g vs 0.08 g for the controls; p # 0.05) as compared with the controls. Similarly, during GD 16 20 body weight gains were slightly less for the mid dose group and significantly (p # 0.01) less for the high dose group (0.00 g for mid dose and 0.12 g for high dose vs 0.02 g for the controls) as compared with the controls. Both mid and high dose groups had significantly (p # 0.05) greater body weight gains as compared with the controls during GD 20 24. Food consumption by the high dose group was significantly (p # 0.05) less than that of the controls on GD 13 16 and 16 20.

In the high dose group, absolute and relative liver weights were increased to 129% (p # 0.01) and 135% (n. s.), respectively of controls.

The maternal toxicity LOAEL was established at 25 mg/ kg/ day based on reduced body weight gain. The maternal toxicity NOAEL was established at 5 mg/ kg/ day.

The number of fetuses( litters) available for evaluation in the control, low, mid, and high dose groups was 135( 20), 135( 20), 121( 17), and 79( 13), respectively. 11 Five high dose does aborted between days 20 25 compared with one control doe on GD 22. The mean number and percentage of resorptions and number of dead fetuses were similar between the treated and control groups. In the high dose group, slight (n. s.) decreases in the mean number of live fetuses/ litter (6.1 vs 6.8 for controls) and mean fetal body weight (41.99 g vs 45.8 g for controls) were observed.

No treatment related external or visceral fetal malformations/ variations were noted. In the control, low, mid, and high dose groups, skull alterations (irregularly shaped fontanelle, hole in parietals, parietals contain intraparietals, and unossified) were observed in 1( 1), 9( 5), 5( 3), and 19( 6) fetuses( litters), respectively. The litter incidence for the high dose group was significantly (p # 0.05) greater than that of the control group. It should be noted that 6 fetuses from 5 low dose litters also had a variety of external malformations of the head and body.

The developmental toxicity LOAEL was established at 100 mg/ kg/ day based on alterations of the bones of the skull. The developmental toxicity NOAEL was established at 25 mg/ kg/ day.

This study is classified as Acceptable/ Guideline and does satisfy the guidelines for a developmental toxicity study [OPPTS 870.3700 (83 3b)] in rabbits.

4.4 Reproductive Toxicity Adequacy of data base for Reproductive Toxicity: The data base for reproductive toxicity is considered complete and no additional studies are required at this time.

4.4.1 870.3800 Three Generation Reproduction and Fertility Effects  Rat Executive Summary: In a three generation reproduction study (MRID No.: 00146071 & 00155168), Linuron (94.5% a. i.) was administered to groups of 20 male and 20 female Crl: CD® rats in the diet at concentrations of 0, 25, 125, or 625 ppm. Two litters were produced by the F0 and F1 generations and one litter was produced by the F2 generation. Average premating doses were 0, 2, 9, and 44 mg/ kg/ day, respectively, for F0 males; 0, 2, 10, and 50 mg/ kg/ day, respectively, for F0 females; 0, 2, 9, and 50 mg/ kg/ day, respectively, for F1 males; 0, 2, 11, and 59 mg/ kg/ day, respectively, for F1 females; 0, 2, 9, and 48 mg/ kg/ day, respectively, for F2 males; and 0, 2, 11, and 67 mg/ kg/ day, respectively, for F2 females. F1 and F2 adults were chosen from the F1b and F2b litters, respectively. F0, F1, and F2 male and female parental animals were administered test or control diet for at least 90 days prior to mating, throughout mating, gestation, and lactation, and until necropsy. At weaning 10 F2b pups/ sex/ group were subjected to gross necropsy with microscopic examination of selected tissues. Following the reproductive toxicity evaluations, F1 and F2 adults were maintained on their respective diets, for up to a total of 22 months on study, for hematological evaluations (MRID 00155168).

Premature deaths of several adults in each generation were considered incidental to treatment. No treatment related clinical signs of toxicity were observed in males or females during premating in any generation. Necropsy findings were not reported for 12 adults. No effects on body weights or body weight gains were seen in the low dose groups of any generation; food consumption and food efficiency were not affected by treatment.

Body weights of the high dose parental animals were significantly (p # 0.05) less than those of the controls beginning on day 7 for the F0 adults and throughout premating for the F1 and F2 adults. Compared with their control levels, body weights for the high dose males and females were 83 90% and 88 93%, respectively, for the F0 adults, 77 81% and 74 87%, respectively, for the F1 adults, and 72 79% and 74 81%, respectively, for the F2 adults. Premating weight gains for the high dose males and females were significantly (p # 0.05) less than those of the controls in all generations. Body weights of the mid dose males were less than those of the controls during each generation, but statistical significance was reached only occasionally. Body weights of the mid dose females from all generations were 88 94% of the control levels with statistical significance (p # 0.05) attained at most time points. Lower body weights of the mid and/ or high dose dams after weaning of their litters were considered a continuation of the premating effects on body weights.

Hematology results for the F1 rats were inconclusive. No treatment related hematological effects were noted in F2 males after continuous feeding for 20 months. However, for F2 females a mild anemia was observed in the mid and high dose groups at 20 and 22 months. In mid and high dose females, RBC counts were decreased to 90 91% of the controls, hemoglobin was decreased to 89 93% of controls, and the percent of reticuloytes was increased to 147 213% of the control levels. Although statistical significance was not attained for all endpoints at both sampling intervals, the changes in red cell parameters are considered to be biologically significant.

Treatment related lesions observed in the liver of high dose F2b weanlings are considered systemic toxicity. In the control, low, mid, and high dose groups, the incidence (average severity) of hepatocellular atrophy was 1/ 10 (2.0), 0/ 10 (0), 2/ 10 (1.5), and 8/ 10 (2.1), respectively, for males and 2/ 10 (3.0), 1/ 10 (3.0), 2/ 10 (2.0), and 10/ 10 (2.5), respectively, for females. The incidence and severity of decreased cytoplasmic vesiculation was the same as that of hepatocellular atrophy for all groups except the high dose males in which 10/ 10 were affected with an average severity score of 2.0.

The LOAEL for systemic toxicity was established at 125 ppm (average premating dose 9 mg/ kg/ day, males and 10 mg/ kg/ day, females) based on reduced body weights of males and females and anemia in females. The systemic toxicity NOAEL is 25 ppm (premating dose 2 mg/ kg/ day in males and females).

Fertility, pup survival, and pup body weights were not affected in the low or mid dose groups in any generation. In the high dose groups, fertility was decreased with each successive litter and generation. The fertility indices for production of the F1a, F1b, F2a, F2b, and F3 litters were 100, 89.5, 63.2, 61.1, and 52.6%, respectively. Mean live litter size at birth and pup viability during lactation days 0 4 were significantly (p # 0.05) or slightly reduced for all litters produced by the high dose groups. Both of these 13 parameters generally declined with each successive litter and generation. Mean live litter sizes were 6.2 9.3 pups for the high dose groups compared with 11.7 13.3 pups for the control groups. Viability indices for lactation days 0 4 were 58.8 92.0% for the highdose litters compared with 92.1 100% for the control litters.

The reproductive toxicity LOAEL was established at 625 ppm (premating dose 44 mg/ kg/ day in males and 48 mg/ kg/ day in females) based on reduced fertility. The reproductive toxicity NOAEL is 125 ppm (average premating dose 9 mg/ kg/ day in males and 10 mg/ kg/ day in females).

Body weights of the high dose pups from all generations were consistently reduced throughout lactation as compared to those of the controls with statistical significance (p # 0.05) attained at most time points. Body weights of the high dose pups from both litters of the F1 and F2 generations were approximately 82 94% of the control levels one day after birth and declined to approximately 66 80% of the control levels at weaning. In contrast body weights of the high dose F3 pups were 84 89% of the controls throughout lactation. Differences in absolute and/ or relative organ weights in high dose F2b weanlings were considered to be due to lower final body weights.

The offspring toxicity LOAEL was established at 625 ppm (premating dose 44 mg/ kg/ day, males and 48 mg/ kg/ day, females) based on decreased pup survival and lower pup body weights. The offspring toxicity NOAEL is 125 ppm (average premating dose 9 mg/ kg/ day in males and 10 mg/ kg/ day in females).

This study is classified as Acceptable/ Guideline and satisfies the requirements for a reproduction study (870.3800 [83 4]) in rats.

4.4.2 870.3800 Two Generation Reproduction Study in the Rat Executive Summary: In a two generation reproduction study (MRID No: 41463401), linuron (96.2% a. i.) was administered to groups of 30 male and 30 female Crl: CDBR rats in the diet at concentrations of 0, 12.5, 100, or 625 ppm. One litter was produced by each generation. Average premating doses for the treated F0 groups were 0.74, 5.8, and 36 mg/ kg/ day, respectively, for males and 0.92, 7.3, and 45 mg/ kg/ day, respectively, for females. Average premating doses for the treated F1 groups were 0.95, 7.8, and 54 mg/ kg/ day, respectively, for males and 1.1, 9.2, and 63 mg/ kg/ day, respectively, for females. F0 and F1 parental animals were administered test or control diet for 72 or 75 days, respectively, prior to mating and throughout mating, gestation, and lactation, and until necropsy.

No treatment related clinical signs of toxicity or mortalities were observed in the adult animals of either generation.

Body weights, body weight gains, and food consumption were significantly (p # 0.05) less than those of the controls beginning on day 7 for the high dose F0 animals and throughout premating for the mid and high dose F1 animals. At the end of premating, body weights of the high dose F0 males and females were 81% and 86%, respectively, of 14 the controls with overall weight gains 59% and 55%, respectively, of the control values. For the high dose F1 males and females final premating body weights were 76% and 75%, respectively, with weight gains 77% and 77%, respectively, of the control levels. Mean daily food consumption levels for the high dose groups during the premating interval were 80 85% of the control levels. Absolute body weights of the mid dose F0 males were occasionally significantly (p # 0.05) less than the controls with premating weight gains and food consumption 88% and 94% (both, p # 0.05), respectively, of the control levels. For the mid dose F1 males and females, final premating body weights, body weight gains, and food consumption were 92 94% of the control levels. For the mid and high dose dams of both generations, lower body weights during gestation and lactation were considered a continuation of premating effects.

No treatment related lesions were noted at necropsy of the F0 males or females. In highdose F1 males, gross lesions of the testes included reduced in size (9/ 30), abnormally large (3/ 30), soft (5/ 30), small epididymides (8/ 30), and unspecified deformities of the epididymides (5/ 30). Microscopically, increased incidences (p # 0.05) of testicular and epididymal lesions were found in high dose F1 males as compared with the controls: atrophy (14/ 30), fibrosis (8/ 30), and hyperplasia (7/ 30) in the testes and arteritis (6/ 30), inflammation (5/ 30), and oligospermia (12/ 30) in the epididymides. Only one incidence each of atrophy and oligospermia were observed in control animals. Absolute testes weights of the high dose F1 males were significantly (p # 0.05; 80% of control) less than the controls. In high dose F1 females, gross findings (n. s.) included cystic ovaries (4/ 30), dilatation (3/ 30), and fluid filled uterine horns (2/ 30), none of which were observed in control animals.

In addition, lesions of the eye were noted in high dose F1 males and females and were reviewed in MRID 41864701. A significant (p # 0.05) increase was seen in the number of high dose F1 males with any type of corneal or conjunctival change (14/ 30 vs 4/ 30 controls). The lesions included corneal degeneration/ basophilia and conjunctival inflammation/ basophilia. Degeneration of the lens was observed in 3/ 30 high dose males and 3/ 29 high dose females compared with only 1/ 30 control male. However, a clear treatment related effect in females was not considered to be definitive.

The systemic toxicity LOAEL was established at 100 ppm (average premating doses 5.8 9.2 mg/ kg/ day) based on reduced body weight gains in males and females during both generations. The systemic toxicity NOAEL was established at 12.5 ppm (average premating doses 0.74 1.1 mg/ kg/ day).

No treatment related adverse effects were found on the reproductive performance of either generation. For the control, low, mid, and high dose group, pup viability for lactation days 0 4 was 99.4, 98.0, 99.8, and 91.7% (p # 0.05), respectively, for the F1 generation and 96.8, 92.7, 99.5, and 76.2% (p # 0.05), respectively, for the F2 generation. The mean number of pups per litter in the high dose F2 group was significantly (p # 0.05) less than the control throughout lactation. The number of litters with pups showing clinical signs was significantly (p # 0.05) increased in both generations. 15 The reproductive toxicity NOAEL was greater than or equal to 625 ppm (average premating doses 36 63 mg/ kg/ day) and the reproductive toxicity LOAEL was not established.

Body weights of the mid and high dose F1 male and female pups and of the high dose F2 male and female pups were significantly (p # 0.05) less than those of the controls throughout lactation LOAEL for offspring toxicity was established at 100 ppm (average premating doses 5.8 9.2 mg/ kg/ day) based on reduced F1a, b and F2a, b pup body weights. The offspring toxicity NOAEL was established at 12.5 ppm (average premating doses 0.74 1.1 mg/ kg/ day).

This study is classified as Acceptable/ Guideline and satisfies the guideline requirements for a reproductive toxicity study [OPPTS 870.3800 (83 4)] in rats.

4.5 Chronic Toxicity Adequacy of data base for chronic toxicity: The data base for chronic toxicity is considered complete and no additional studies are required at this time.

4.5.1 870.4300 Combined Chronic Toxicity/ Carcinogenicity Study CD( SD) BR Rats Executive Summary: In a chronic toxicity/ oncogenicity study (MRID 00029680 and MRID 00029679), INZ 326 (Linuron; 96.9 97.2% a. i.; Lot No. 20427, Batch No. 90, E 6110 29B) was administered in the diet to groups of 70 ChR CD1 rats/ sex/ dose at concentrations of 0, 50, 125, and 625 ppm (0, 2.1, 5.1, and 27 mg/ kg/ day for males and 0, 3.1, 7.8, and 48 mg/ kg/ day for females) for up to 2 years. Additional groups of 10 rats/ sex/ dose were administered the same diets for 12 months for interim evaluation. All clinical pathology data were reanalyzed (MRID 00 164117) due to inappropriate statistical methods used in the original study report.

Linuron had no effect on mortality at any dose, and there were no treatment related clinical signs reported. Absolute body weights of the high dose male group were decreased to 88 91% of controls during weeks 1 19, with decreased body weight gain during weeks 0 13 and 52 104 resulting in body weight gain for the entire study being 89% of controls. Absolute body weights of the high dose female group were decreased throughout the study, with the magnitude of the decrease generally increasing throughout the course of the study. The body weight gain of this group for the entire study was 57% of controls. Body weight gain by mid dose males was decreased to 64% of controls during the week 52 76 interval, with body weight loss during the week 76 104 interval being increased to 148% of controls. Body weight gain by the mid dose female group was decreased to 75% of controls during the week 52 76 interval. There were no toxicologically significant treatment related effects on food consumption; however, food efficiency values of high dose females were decreased to 74 88% of controls during weeks 1 4 and to 58% of controls for the entire study period. 16 Histopathology observations consistent with hemolysis were observed at increased incidences in high and mid dose males and females from the main study and interim sacrifice groups, including hemosiderin in Kupffer cells and increased hemosiderosis in bone marrow, spleen, and/ or mesenteric lymph nodes, and transient decreases in the erythrocyte count, hemoglobin concentration, and hematocrit of the high dose female group were noted at 6 and/ or 12 months..

Male rats of the main study group had significantly increased incidences of mineralization/ calculi in the renal pelvis, transitional cell hyperplasia in the renal pelvis, and subacute perivasculitis and/ or vasculitis in the epididyinides at the mid and highdose treatment levels. Female rats of the main study group had significantly increased incidences of calculi in renal tubules at the mid and high dose treatment levels and significantly increased incidences of hepatic sinusoidal ectasia and collecting duct ectasia in the kidney at the high dose treatment level. The high dose female group also had a non statistically significantly increased incidence of transitional cell hyperplasia in the renal pelvis compared to controls. Hepatocellular megalocytosis/ syncytium formation with fibroplasia radiating between hepatic cords, and occasional increased hepatocellular intracytoplasmic basophilia was only observed in the main study high dose female group (15/ 68 animals examined at that site) and may have been related to induction of hepatocellular protein synthesis. The significance of this finding is unknown but considered adverse.

The lowest observed adverse effect level (LOAEL) for Linuron in ChR CD' rats is 125 ppm (5.1 mg/ kg/ day for males and 7.8 mg/ kg/ day for females), based on decreased body weight gains in both sexes, microscopic observations consistent with hemolysis (hemosiderin in Kupffer cells and increased hemosiderosis in bone marrow, spleen, and/ or mesenteric lymph nodes), and increased incidences of microscopic changes in the epididymides (perivasculitis/ vasculitis) and renal pelvis (transitional cell hyperplasia and mineralization/ calculi) of males and kidneys (calculi in renal tubules) of females. The corresponding no observed adverse effect level is 50 ppm (2.1 mg/ kg/ day for males and 3.1 mg/ kg/ day for females).

There was a treatment related increase in the incidence of testicular interstitial adenomas at the 125 and 625 ppm treatment levels (5.7, 27.5, and 53.6% for control, mid, and high dose males, respectively; p< 0.01). Common neoplasms, included pituitary adenomas of the pars anterior in both male and female rats and mammary fibroadenomas in female rats. Decreased incidences of both these tumor types were noted in the highdose female group. Dosing was considered adequate based on the decreases in body weight and body weight gain of high dose females.

This chronic toxicity/ oncogenicity study in the rat is Acceptable/ Guideline and does satisfy the guideline requirement for a chronic toxicity/ oncogenicity oral study [OPPTS 870.4300 (§ 83 5)] in the rat; however, it must be noted that results from concentration and stability analyses indicate potential variation between nominal and actual diet concentrations which make the exact doses to the animals questionable 4.5.2 870.4100b Chronic Toxicity  Dog 17 Executive Summary: In a one year chronic toxicity study, linuron (96.2% a. i., Batch No. 16,569) was administered to groups of 4 male and 4 female beagle dogs in the diet at concentrations of 0, 10, 25, 125, or 625 ppm (MRID 40952601). Time weighted average doses for the treated groups were 0.29, 0.79, 4.2, and 19 mg/ kg/ day, respectively, for males and 0.30, 0.77, 3.5, and 16 mg/ kg/ day, respectively, for females.

No treatment related clinical signs of toxicity or mortalities were observed at any dose level. Body weights, body weight gains, and food consumption were not affected by treatment. No treatment related ophthalmological lesions or changes in urinalysis parameters were noted and gross necropsy was unremarkable.

RBC counts, hemoglobin, and hematocrit were slightly (n. s.) decreased throughout the study in high dose males and females as compared with those of the controls. WBC and platelet counts were significantly (p # 0.05) increased in high dose females at 3, 6, and 9 months and platelet counts were increased (p # 0.05) in high dose males at 3 months. Methemoglobin and sulfhemoglobin levels were significantly (p # 0.05) increased in the 625 ppm males and females at all time points as compared with those of the controls. In addition, for the 125 ppm groups methemoglobin levels were increased (p # 0.05) in males and females at 3 and 6 months while sulfhemoglobin levels were (p # 0.05) increased at 9 months in males and at 3, 9, and 12 months in females. Increased hematopoiesis was observed in the bone marrow from 3/ 4 high dose males and 4/ 4 highdose females, compared with none of the control males and only 1/ 4 control females.

Cholesterol levels were increased in the high dose groups at all time points as compared with control levels with statistical significance (p # 0.05) attained at 3, 6, 9, and 12 months for males and 3 months for females.

Absolute liver weights were slightly (n. s.) increased in the 625 ppm males and relative liver weights were significantly (p # 0.05) increased in the 125 and 625 ppm males. No effects on liver weights were noted in females.

Increases in the incidence and/ or severity of brown pigment (hemosiderin) deposition in the liver were observed microscopically in high dose males and females.

The LOAEL for linuron in male and female beagle dogs was established at 125 ppm (4.2 mg/ kg/ day, males and 3.5 mg/ kg/ day, females) based on abnormal hematology findings (increased met and sulfhemoglobin levels). The NOAEL was established at 25 ppm (0.79 mg/ kg/ day, males and 0.77 mg/ kg/ day, females).

This study is classified as Acceptable/ Guideline and satisfies the guideline requirements for a chronic toxicity study [OPPTS 870.4100 (83 1b)] in dogs.

4.5.3 870.4100b Chronic Toxicity  Dog Executive Summary: In a 2 year chronic toxicity study (MRID 00018374), H 326 (Lot no. not given, purity not given) was administered in the diet to three dogs/ sex at doses of 18 0, 25, 125, or 625 ppm. Average doses to animals were not measured or calculated.

No treatment related mortality occurred and no clinical signs of toxicity were reported during the study. One mid dose male was sacrificed after 47 weeks due to a neurological disorder not related to treatment. Food and water consumption were not monitored. There were no statistically significant effects on absolute or relative organ weights. Treatment with the test material did induce a slight decrease (8.5%) in the body weight of high dose female dogs, as well as a slight decrease in body weight gain. These effects were not observed in male dogs and were not considered biologically or toxicologically relevant in females.

At necropsy, no significant changes in gross pathology were observed at any treatment level. Hematocrit, hemoglobin, and erythrocyte counts were slightly but statistically significantly (p # 0.05) reduced in male dogs at 625 ppm after 104 weeks of treatment. Corroborating microscopic pathology data indicated hemosiderin deposition in liver Kupffer cells of 6/ 6 dogs and erythroid hyperplasia in the bone marrow of 3/ 6 dogs (1 male and 2 females) in this group.

Under the conditions of this study, the LOAEL for the systemic toxicity of H 326 in male and female beagles is 625 ppm based on mild hemolytic anemia and secondary erythropogenic activity evidenced by slightly reduced hemoglobin, hematocrit, and erythrocyte counts accompanied by hemosiderin deposition in liver Kupffer cells and erythroid hyperplasia of bone marrow. The NOAEL is 125 ppm.

For a variety of reasons discussed in the study deficiencies, this chronic toxicity study is classified as Unacceptable/ Guideline and does not satisfy the Subdivision F requirements for a chronic oral toxicity study in non rodents [OPPTS 870.4100 (§ 83 1)].

4.6 Carcinogenicity Adequacy of data base for Carcinogenicity: The data base for carcinogenicity is considered complete and no additional studies are required at this time.

4.6.1 870.4200b Carcinogenicity Study  Crl: CD 1 (ICR) BR Mouse Executive Summary: In an oncogenicity study (MRID 00124195), INZ 326 (97.0% a. i., Haskell Laboratory identification no. 10720) was administered to groups of 80 male and 80 female Charles River CD® 1 mice in the diet at concentrations of 0, 50, 150, or 1500 ppm. The test diets were given for 24 months. The concentrations of 50, 150, and 1500 ppm resulted in mean daily compound intakes for males of 8, 23, and 261 mg/ kg/ day; and for females of 12, 35, and 455 mg/ kg/ day, respectively, calculated from food intake and body weight measurements.

No significant treatment related effects were seen in clinical signs or survival. Body weights were consistently and significantly lower in males and females at 1500 ppm than in the control groups throughout the study. At 52 weeks, the group mean body weights and weight gains of high dose males were 8% and 15% lower than the controls, 19 respectively, and high dose females were decreased by 11% and 21%. At 104 weeks, the body weights and weight gains of high dose males were 10% and 20% less than the controls, and in high dose females were 8% and 14% less than the controls, respectively. The overall food intake for high dose males was decreased by about 14% and by 10% for high dose females compared to the controls. Food efficiency for the 2 year study was not significantly affected in treated animals.

Increases of 9 18% in group mean erythrocyte cell volume and mean cell hemoglobin were seen in males and females after 6 months of treatment at 1500 ppm. Erythrocyte counts were decreased by 9% and 14% in high dose males and females, respectively, compared to the controls at 6 months. These hematology values returned to near control levels later in the study. A significant increased incidence of hemosiderin deposits in the spleens of both sexes at 1500 ppm is suggestive of a compensated hemolytic anemia in high dose animals. Methemoglobin levels were increased in high dose females by 117% compared to the control group, and were increased in high dose males by 613% compared to the 50 ppm group (the male control value was not available). Differential white cell counts were within normal parameters for both sexes at all doses.

The absolute and relative (to body) liver weights were increased by 20% and 24%, respectively in high dose males and by 65% in high dose females compared to the controls. Microscopic evidence of liver toxicity at 1500 ppm included increased incidences of focal hepatocellular cytoplasmic alteration, focal centrilobular peliosis, and centrilobular hepatocytomegaly in both sexes, and increased incidence of hepatocellular cytoplasmic vacuolation in females.

The LOAEL for INZ 326 in mice is 1500 ppm in the diet for males (261 mg/ kg/ day) and females (455 mg/ kg/ day), based on microscopic liver changes, methemoglobinemia, and decreased body weight and weight gain in both sexes. The NOAEL was 150 ppm for males (23 mg/ kg/ day) and females (35 mg/ kg/ day).

Treatment of up to 104 weeks with 1500 ppm INZ 326 resulted in a significant increase in the incidence of hepatocellular adenomas (control, 6%; 1500 ppm, 25%, p < 0.05) in female Charles River CD® 1 mice under the conditions of this study. Dosing was considered adequate based on the liver changes, methemoglobinemia, and decreased body weights.

This oncogenicity study in the mouse is Acceptable (Guideline) and does satisfy the guideline requirement for an oncogenicity study [OPPTS 870.4200 (§ 83 2)] in mice. There were a number of deficiencies in this study, but none that would alter the conclusions reached through the available data.

Adequacy of the Dose Levels Tested: Dosing was considered adequate based on the decreases in body weights, body weight gains and other systemic effects (microscopic liver changes, methemoglobinemia) in high dose males (261 mg/ kg/ day) and females (455 mg/ kg/ day). The chronic/ oncogenicity study presented above in section 4.5 (870.4100a) satisfies the data requirements for 870.4200a. 20 4.6.2 870.4300 Carcinogenicity Study CD( SD) BR Rats The executive summary for the chronic/ oncogenicity study is presented above in section 4.5.1 (870.4300) satisfies the data requirements for 870.4300.

4.7 Mutagenicity Adequacy of data base for Mutagenicity: The submitted test battery satisfies the Pre1991 mutagenicity initial testing battery guidelines. No further testing is required at this time.

Gene Mutation 870.5100 Bacterial reverse gene mutation assay MRID 00131738 Acceptable In a reverse gene mutation assay in bacteri, S. typhimurium strains TA98, TA100, TA1535, and TA1537 were exposed to Linuron (95 97%, lot number not given) in dimethylsulfoxide at concentrations of 0.5, 0.75, 1.0, 2.5, and 5.0 : g/ plate in the absence of mammalian metabolic activation (S9 mix) and 1, 5, 10, 50, and 100 : g/ plate in the presence of S 9 mix. There was no evidence of induced mutant colonies over background with or without S9 activation.

870.5300 CHO/ HGPRT cell forward gene mutation assay MRID 00137152 Acceptable In a mammalian cell gene mutation assay in vitro, triplicate (in the absence of activation) or duplicate (in the presence of activation) cultures of Chinese hamster ovary (CHO) CHO K1 BH4 cells were exposed to Linuron (Lot No. 1N2 326 141, 94.5% a. i.) in F12 medium at concentrations of 0.05, 0.25, 0.35, 0.40, 0.45, and 0.50 mM in the absence of mammalian metabolic activation (S9 mix), and at 0.25, 0.50, 0.75, 0.90, and 1.0 mM in the presence of Charles River S9 mix. The S9 fraction was obtained from Aroclor 1254 induced 8 to 9 week old male Charles River CD rats.

Linuron was tested up to concentrations limited by cytotoxicity. Cytotoxicity was observed at 0.45 and 0.5 mM under nonactivated conditions and at 0.75 mM and above with 0.5 mg S9 protein/ mL and at 1.0mM and above with 1.0 mg S9 protein/ mL. (Percentage cell survival were not provided in the DER). There was no increase in mutant frequency in cells treated with linuron in either the presence or absence of metabolic activation. The positive (ethyl methane sulfonate (EMS) without S9 mix and dimethylbenzanthracene with S9 mix) and solvent (DMSO) controls responded appropriately. No evidence of an increased mutant frequency was observed in the presence or absence of metabolic activation.

Cytogenetics 21 870.5385 In vivo bone marrow chromosomal aberration assay MRID 00137153 Acceptable In a mammalian cell cytogenetics chromosomal aberration assay in bone marrow cells of Sprague Dawley rats, 5 rats per sex per harvest time were administered Linuron (94.5%, lot number not given) by single gavage at doses of 0, 100, 300, or 1000 mg/ kg. Bone marrow cells were harvested 6, 12, 24, or 48 hours after test compound administration and 48 hours after the positive control dose. The vehicle was corn oil (20 mL/ kg) and the positive control was a single 40 mg/ kg dose of cyclophosphamide.

One high dose rat in the 24 hour group was found dead and 8 of 10 highdose rats in the 48 hour group died prior to sacrifice on day 2. Low and mid dose animals exhibited slight depression, ataxia, and/ or prostration. Treated animals also had decreased body weights compared to controls. There was no significant increase in the frequency of aberrations in bone marrow cells of treated animals compared to controls at any sampling time. Values in treated animals ranged from 0.3 0.8% aberrant cells/ group; the positive control group had 19.6% aberrant cells, indicating that this control responded appropriately. There was no change in mitotic index of dosed groups compared to controls. There is no evidence that Linuron induced chromosomal aberrations in bone marrow cells of rats over background levels.

Other Genotoxicity 870.5550  Unscheduled DNA synthesis in mammalian cell culture MRID 00132583 Acceptable In an unscheduled DNA synthesis assay, primary rat hepatocyte cultures were exposed to Linuron (94.5% a. i. in dimethylsulfoxide; Lot No. T80311 81) in Williams' Medium E (WME) at concentrations of 0.00001, 0.0001, 0.001, 0.01, 0.1, 1.0, 10, and 50.0 mM (trial 1) or 0.01, 0.1, 1.0, 10, and 50.0 mM (trial 2) for 18 hours. There is no evidence that Linuron induced chromosomal aberrations in bone marrow cells of rats over background levels.

4.8 Neurotoxicity Adequacy of data base for Neurotoxicity: No acute or subchronic neurotoxicity studies on Linuron are available. Evaluation of subchronic, chronic and reproduction toxicity, did not reveal any treatment related effects on the central or peripheral nervous system of mice, rats, or rabbits. No changes in clinical signs, brain weights, gross necropsy results or histopathological results suggested any part of the nervous system as a target organ. However, the HIARC (Nov 20, 2001) determined that a developmental neurotoxicity study in the rat is required based on the finding that linuron is an endocrine disruptor, increased testicular lesions and decreased fertility.

4.8.1 870.6100 Delayed Neurotoxicity Study  Hen This study is not required.

4.8.2 870.6200a Acute Neurotoxicity Screening Battery This study is not required. 22 4.8.3 870.6200b Subchronic Neurotoxicity Screening Battery This study is not required.

4.8.4 870.6300 Developmental Neurotoxicity Study This study is required.

4.9 Metabolism Adequacy of data base for metabolism: The data base for metabolism is considered complete and no additional studies are required at this time.

4.9.1 870.7485 Metabolism  Rat Executive Summary: In a metabolism study (00146489, 40142401, 41960001, 42006801), linuron was administered by gavage to male and female rats at single doses of 24 or 400 mg/ kg/ day, Linuron was extensively metabolized by male and female rats at both the low and high dose levels. The biological half life was affected by sex and dose level and ranged from 21 hours in the low dose males to 56 hours in the high dose females. Total recovery of radioactivity was 96% in males and 97% in females. At 400 mg/ kg, the majority of the administered 14 C linuron was eliminated in the urine (81% in males and 72% in females) and, to a lesser extent, in the feces (15% in males and 20% in females). In general, tissue and organ residues were very low (< l%) at both dose levels, and there was no indication of accumulation or retention of linuron or its metabolites. The major metabolites identified in the urine were hydroxy norlinuron (59% in males and 64% in females), desmethoxy linuron (11% in males and females) and norlinuron (3% in males and 2% in females), and in feces, hydroxy norlinuron,( 28% in males and 32% in females) and norlinuron (28% in males and 23% in females). Neither hydroxy 3,4 dichloroanaline nor 3,4 dichloroanaline were present in any of the samples. Exposure to linuron appeared to induce mixed function oxidative enzymes.

This metabolism study in the rat is Acceptable/ Guideline and satisfies the guideline requirement for a metabolism study [OPPTS 870.7485 (§ 85 1)] in the rat.

4.9.2 870.7600 Dermal Absorption  Rat Executive Summary: In this dermal absorption study (MRID 163837), four grous of 20 rats (one female group and three male groups) were dosed with 14 C (2.35 : Ci/ mg) linuron at 0.12, 1.00, or 7.4 mg/ 2 in 2 (2.82, 23.5, or 17.4 : Ci, respectively).

Based on the results of this study, a dermal absorption factor of 16% was observed for an exposure of 8 to 10 hr (2%/ hr).

4.10 Special Studies 4.10.1 Biochemical and Histopathological Effects in Rats 23 Executive Summary: A special study (MRID No: 00164093) was conducted to determine the biochemical and histopathological effects under a variety of conditions of linuron (94.5% a. i.) administration to Crl: CD® BR rats. The rats utilized for various parts of this study were young adult males approximately 22 days old (young), retired breeder males approximately 11 months old (old), and male and female F1b and F2b rats from a multigeneration study (MRID 41463401) maintained on diets of 0, 12.5, 100, or 625 ppm (0, 0.75, 4.1, and 22 mg/ kg/ day, respectively, for males and 0, 1.1, 6.1, and 37 mg/ kg/ day, respectively, for females). Additionally, Leydig cell enzyme analyses were conducted in vitro.

The activities of five testicular steroidogenic enzymes were assayed in vitro using horse testicular microsomal preparations in the presence of 0, 0.5, 5, 50, 500, or 5000 : M linuron or linuron metabolites. Enzyme activities measured included aromatase, 17 20 desmolase (desmolase), 3 $ hydroxysteriod dehydrogenase/ isomerase (isomerase), 17 hydroxylase (hydroxylase), and 17 ketosteriod reductase (reductase). Linuron concentrations of 500 and 5000 : M resulted in significantly decreased aromatase and desmolase and increased reductase activities. At 50 : M the activities of aromatase, desmolase, isomerase, and hydroxylase were decreased by 10 20% and reductase was increased by 20% as compared with the controls. Effects of linuron metabolites on enzyme activities were highly variable and generally only seen at 5000 : M.

The testosterone metabolic clearance rate was measured in young male rats. Groups of 5 animals were administered 0 or 200 mg/ kg/ day for eight days, castrated, and then infused with testosterone at 3 or 6 : g/ hour. Blood samples were taken every 30 minutes for 180 minutes after the start of infusion. No differences between the treated and control groups were noted at the lower infusion rate. At the higher infusion rate, the mean plateau concentrations (60 180 minutes) in the control and treated rats were 769± 344 and 605± 67.4 : g/ dL, respectively, resulting in calculated metabolic clearance rates of 780 and 992 mL/ h, respectively. Due to the large variability between individual animals it was concluded that linuron does not affect testosterone clearance in young, castrated rats.

Two trials evaluated the response of Leydig cells to luteinizing hormone (LH). In trial 1, the groups consisted of five young or five old males treated with 0 or 200 mg/ kg/ day for three days, and five 0 ppm and five 625 ppm F2b males which were approximately 11 months old. In trial 2, the groups consisted of five young or five old males treated with 0 or 200 mg/ kg/ day for seven days, and five each of the 0, 12.5, 100, and 625 ppm F2b males which were approximately 19 months old. Leydig cells were isolated from the testes and incubated with up to 1000 ng LH/ tube. Results from trial 1 showed no differences in the response between the treated and control young rats. However in old rats, Leydig cells from the treated animals were less responsive than the controls both in maximum response and potency. In contrast, Leydig cells from the chronically treated F2b males were significantly more responsive to LH stimulation as compared with their controls. In trial 2, Leydig cells from treated young and old rats had decreased maximum responses and potency as compared with controls, with old rats more affected than young rats. From the chronically exposed rats, Ledig cells were moderately responsive from the control and low dose groups, minimally responsive from the mid dose group, but 24 significantly greater in response from the high dose group. Taken together, the two trials were reasonably consistent with a preliminary conclusion that there are dose and timerelated effects of linuron upon the sensitivity of rat Leydig cells to stimulation by LH.

F1b and F2b rats were sacrificed at two years of age for histopathological evaluation of selected tissues. The number of high dose males of both generations with small or discolored testes was increased as compared with the controls (stated in text of DER; incidence rates not readable). No other gross observations were noted. Microscopically, mid and high dose males had increased incidences of interstitial cell adenomas and hyperplasia. Combining data from both generations, adenomas were observed in 1/ 19, 0/ 25, 6/ 25, and 2/ 16 animals and hyperplasia was observed in 2/ 19, 0/ 25, 7/ 25, and 3/ 19 animals from the control, low, mid, and high dose groups, respectively. The lower incidences in the high dose group were probably due to fewer animals available for examination. In females the combined incidence rate for cervical endometrial hyperplasia was 0/ 28, 6/ 30, 9/ 29, and 13/ 29, respectively, and of cervical cystic hyperkeratosis was 0/ 28, 1/ 30, 1/ 29, and 7/ 29, respectively. These lesions in both males and females are consistent with findings in a 2 year chronic study.

In conclusion, the biochemical and histopathological data presented in this report suggest that linuron may affect testosterone metabolism in horse testicular microsomes for a range of concentrations which overlap the dose levels given rats chronically. However, the net effect of these enzyme changes and the relevance to the rat in vivo are uncertain. Evidence in young and old rats exposed repeatedly (3 7x) or for 11 or 19 months suggests that Leydig cell incubates are differentially altered in their sensitivity to LH. Microscopic lesions in the testes and cervix have been confirmed in other studies.

This study is classified as Acceptable/ Nonguideline as a special mechanistic study in rats.

4.10.2 Leydig Cell Tumorigenisis in Rat Executive Summary: A special mechanism study (MRID No: 41630101) was conducted in male Crl: CD( SD) BR rats. Linuron (96.2% a. i) was administered at 200 mg/ kg/ day by gavage for 14 days to groups of 10 growing (32 33 days of age) and adult (93 days of age) rats. Additional groups of 10 rats each were used as negative control, pair fed control, and positive control (flutamide, 10 mg/ kg/ day). All rats were observed daily and body weights and food consumption were recorded. At termination, blood was collected for serum hormone analyses and the organs of the reproductive tract were weighed. In addition, blood was collected from the F0 and F1 males and organ weights were recorded from the F0 males from a multigeneration study (MRID 41463401). Premating doses for the multigeneration study were 0.74 0.95, 5.8 7.8, and 36 54 mg/ kg/ day. Finally, linuron and four of its metabolites were evaluated in vitro for their ability to compete for binding to the androgen receptor.

No treatment related clinical signs of toxicity were observed in the growing rats, the positive controls, or the F0 and F1 rats. Adult rats treated with the test article for 14 days had significantly (p # 0.05) increased incidences of discharge and/ or stains in the perioral, perinasal, and or periocular regions (9/ 10), eye discharge (5/ 10), and weak 25 appearance (9/ 10) as compared with both the negative and pair fed control groups. These signs were not observed in the control groups with the exception of one pair fed animal with discharge and/ or stains.

Final body weights, body weight changes, and food consumption of the 14 day treated groups, of the pair fed control groups, and of the mid and high dose F0 and F1 groups were significantly (p # 0.05) less than that of their concurrent negative control group values. Final body weight and weight change for the 14 day adult group were also significantly (p # 0.05) less than those of their pair fed control. Body weights and body weight changes were significantly (p # 0.05) reduced only in the adult positive control group as compared with their negative controls (food consumption not measured in positive controls).

For growing rats, absolute and relative accessory sex organ unit, prostate, ventral prostate, and seminal vesicle weights were significantly (p # 0.05) reduced as compared with both negative and pair fed control groups. Absolute and relative dorsal lateral prostate and levator ani muscle weights and absolute testes weights were significantly (p # 0.05) reduced and relative testes weights were significantly increased (p # 0.05) as compared with the negative controls. Significant (p # 0.05) differences in the pair fed control group as compared with the negative control group included decreased absolute accessory sex organ unit, ventral prostate, dorsal lateral prostate, seminal vesicles, and levator ani muscle weights and relative testes and levator ani muscle weights. In the positive control rats, absolute and relative testes weights were not affected, but all other absolute and relative organ weights were significantly (p # 0.05) less than their negative controls.

For adult rats, absolute and relative accessory sex organ unit, prostate, and ventral prostate weights were significantly (p # 0.05) reduced as compared with both negative and pair fed control groups. Absolute epididymides, seminal vesicle, coagulating gland, and levator ani muscle weights significantly (p # 0.05) reduced as compared with the negative controls. Significant (p # 0.05) differences in the pair fed control group as compared with the negative control group included decreased absolute accessory sex organ unit, coagulating gland, and levator ani muscle weights. In the positive control rats, testes weights were not affected, but all other absolute and relative organ weights were significantly (p # 0.05) or slightly (n. s.) less than their negative controls.

Significant differences (p # 0.05) in organ weights for the high dose F0 males as compared with the controls included decreased absolute epididymides, dorsal lateral prostate, and levator ani muscle weights and increased relative testes, epididymides, and ventral prostate weights. Organ weights were unaffected in the two lower dose groups.

Serum testosterone, estradiol, and luteinizing hormone levels in both growing and adult rats were similar to the control levels. However, F0 and F1 males had significantly (p # 0.05) increased levels of estradiol (155 and 115%, respectively) and luteinizing hormone (175 and 168%, respectively). In the positive control groups, testosterone, estradiol, and luteinizing hormone levels were increased (p # 0.05) 304, 123, and 304%, respectively, in growing rats and 915, 100 (n. s.), and 346%, respectively, in adult rats. 26 Linuron and three other compounds [1 (3,4 dichlorophenyl) 3 methoxyurea; 3,4 dichloroanaline; 3,4 dichlorophenylurea; and 1( 3,4 dichlorophenyl) 3 methylurea] appeared to compete with testosterone for binding to the androgen receptor in vitro, although the results were highly variable. IC50 values for linuron and flutamide were approximately 18,000 ± 3,500 and 64,000± 11,000 nM, respectively. 3,4 dichlorophenylurea did not displace testosterone from the receptor, therefore an IC50 value could not be determined. The remaining metabolites had IC50 ranging from 110,000 to 260,000 nM.

In conclusion, linuron may be a weak androgen receptor antagonist based on decreased accessory sex organ weights for growing and adult rats, increased serum luteinizing hormone levels in F0 and F1 rats, and competitive androgen receptor binding in vitro. These data support the hypothesis that rats exposed to linuron could develop interstitial hyperplasia and subsequent adenomas (Leydig cell tumors) via a mechanism of sustained hypersecretion of luteinizing hormone induced by the antiandrogenic potential of linuron.

This study is classified as Acceptable/ Nonguideline as a special mechanistic study in rats.

4.10.3 Special Reproduction Study  Cross mating  Rat Executive Summary: A special study (MRID 00159846) was conducted to evaluate the effects of linuron (94.5% a. i.) on the reproduction and lactation performance of crossmated male and female Crl: CD®( SD) BR rats. The rats utilized for this study were the F2 adults from a multigeneration study and the current study was initiated within two weeks after weaning of the last F3a litter. High dose (625 ppm) and control animals were cross mated to produce F3b and F3c litters; different pairings were made for production of each litter. The data from the original F2 control group from the multigeneration study was used as control data for the current study, but the animals were not remated. The fertility index was calculated in the report as (no. litters delivered/ no. females mated) x 100. The reviewer calculated the following indices: male fertility index = (no. males impregnating females/ no. males exposed to females) x 100; female fertility index = (no. females conceiving/ no. females exposed to males) x 100; and fecundity index = (no. pregnancies/ no. copulations) x 100.

During production of both litters, the fertility index and the number of pups/ litter at birth and at weaning were reduced as compared with the control values. The fertility indices for control females crossed with treated males and for treated females crossed with control males were 11.8 and 47.4%, respectively, for the F3b litters and 41.2 and 42.1%, respectively, for the F3c litters as compared with 89.5% for the controls. The number of pups/ litter at birth was 4.0 9.2 for the cross mated groups and 13.1 for the controls. At weaning the number of pups/ litter was 4.0 4.3 for the F3b litters and the F3c litters from treated females crossed with control males compared with 8.1 pups/ litter for both the control group and the F3c litters from control females crossed with treated males.

In production of both litters, male and female fertility indices for the groups in which the males were treated were reduced (47 71% for males and 47 60% for females) compared 27 with those for groups in which the females were treated (90 86% for males and 85 85% for females). The fecundity index was reduced only for treated males crossed with control females during production of the F3b litters (25%) as compared with the other groups (56.2 63.6%).

Pup viability was decreased in litters from treated dams mated with control males as compared with litters from control dams mated with treated males. Pup viability for days 0 4 was 77.5% in litters from treated dams and 98.5% in litters from control dams while viability for days 1 4 was 88.6% and 98.7%, respectively. Litter survival was 75% from treated dams compared with 100% from control dams. Mean pup body weights from treated dams were also slightly or significantly (p # 0.05) less than those from the control dams throughout lactation.

The cross mating results suggest that linuron may cause paternally mediated effects based on decreased fertility and fecundity as well as maternally mediated effects based on decreased pup viability and litter survival.

This study is classified as Acceptable/ Nonguideline as a special cross mating study in rats.

5 TOXICITY ENDPOINT SELECTION 5.1 See Section 9.2 for Endpoint Selection Table 5.2 Dermal Absorption For Executive Summary see section 4.9.2 The dermal absorption factor = 16%

5.3 Classification of Carcinogenic Potential 5.3.1 Conclusions Linuron was placed in special review for carcinogenic effects in 1982. Linuron was later classified as a group C carcinogen on the basis of a dose related increase in interstitial cell hyperplasia and adenomas in a two year rat feeding study (00029680) and hepatocellular tumors that appeared in low dose male and high dose female mice in a two year feeding study (00124195). Subsequent review by the HED peer review committee and the Science Advisory Panel again classified linuron as a Group C carcinogen requiring no quantification of human cancer risk [Federal Register 53( 159): 31262].

5.3.2 Classification of Carcinogenic Potential Group C carcinogen 5.3.3 Quantification of Carcinogenic Potential 28 Not quantification of human cancer risk is required 6 FQPA CONSIDERATIONS 6.1 Special Sensitivity to Infants and Children There is no qualitative/ quantitative evidence of increased susceptibility seen in the rabbit developmental study; developmental effects were seen at a dose higher than that causing maternal toxicity. In the rat developmental study, increases in post implantation losses and increases in fetal resorptions/ litter were seen as a dose that caused decreases in maternal body weight and food consumption. The HIARC determined that the developmental effects are not indicative of qualitative evidence of susceptibility, since increases in resorptions were marginal and there was no change in the number of live fetuses to corroborate the increases in postimplantation losses.

There was no quantitative evidence of susceptibility either in the 2 generation or the 3 generation reproduction studies. In the 2 generation study, reduced body weight gains of pups were seen at the same dose that caused decreases in parental body weights. In the 3 generation study, offspring effects (deceased pup survival and pup body weight) were seen a dose ( 44 mg/ kg/ day) higher than the dose that caused decreases in body weight gain in the parental animals (9 mg/ kg/ day).

However, when the reproductive effects were examined, testicular atrophy was seen at the same dose (625 ppm, 45 mg/ kg/ day) in both studies. In both studies, while the F0 males were not affected, testicular lesions and reduced fertility were seen in the F1 males. This effect in the F1 males is an indication of qualitative evidence of susceptibility.

6.2 Recommendation for a Developmental Neurotoxicity Study Although there was no evidence for increased susceptibility in rats, based on the findings that linuron is an endocrine disruptor, increased testicular lesions and decreased fertility, the HIARC concluded that a development neurotoxicity study in the rat is required.

7 OTHER ISSUES None 8 REFERENCES 00018167 E. I. du Pont de Nemours & Company (1978) Teratogenicity Study of 3 (3,4 Dichlorophenyl) 1 methoxy 1 methylurea in Rats: Haskell Laboratory Report No. 33 79. (Unpublished study received Sep13, 1979 under 352 270; CDL: 240982 B)

00018374 Hodge, H. C. and W. L. Downs (1963). Chronic feeding studies of Linuron (Herbicide 326) in dogs. Department of Pharmacology, University of Rochester 29 School of Medicine and Dentistry, Rochester, NY. Laboratory Study ID not given. February 1, l963.

00027625 Consultox Laboratories, Limited (1974) Linuron: Acute Oral and Dermal Toxicity Evaluation: CL74 : 46 : 996G. (Unpublished study received Dec 19, 1977 under 33660 11; submitted by Industrial Prodotti Chimici s. p. a., Novate Milanese, Italy; CDL: 232505 A)

00029679 Everett, R. (1980) Two year feeding study ChR CD rats. Haskell Laboratory for Toxicology and Industrial Medicine, Central Research and Development Department, E. I. du Pont de Nemours and Company, Newark, DE 19711. Pathology Report No. 1 80, February 4, 1980, Unpublished.

00029680 Kaplan, A., L., et. al. (1980) Long term feeding study in rats with 3( 3,4 dichlorophenyl) l methoxy l methylurea (Lorox', linuron: INZ 326). Haskell Laboratory for Toxicology and Industrial Medicine, Central Research and Development Department, E. I. du Pont de Nemours and Company, Newark, DE 19711. Laboratory report number, 100 80, full study date not provided. Unpublished.

00053769 Kapp, R. W. (1975) Final Report: Acute Inhalation Toxicity Study in Rats: Project No. M915 103. (Unpublished study received Dec 19, 1977 under 33660 11; prepared by Hazleton Laboratories America, Inc., submitted by Industria Prodotti Chimici, s. p. a., Novate Milanese, Italy; CDL: 232505 E)

00124195 Wood, C.; et al. (1982) Long term Feeding Study with ... Lorox, Linuron, Inz 326 in Mice: Haskell Laboratory Report No. 758 82. Final rept. (Unpublished study received Jan 13, 1983 under 352 326; submitted by E. I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL: 249255 A; 249256)

00131738 Russell, J. (1983) Mutagenicity Evaluation in Salmonella typhimurium: Haskell Laboratory Report No. 106 83; MR No. 4581 067. (Unpublished study received Oct 26, 1983 under 352 326; submitted by E. I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL: 251571 A)

00132583 Chromey, N.; Horst, A.; McCooey, K. (1983) Unscheduled DNA Synthesis/ Rat Hepatocytes in vitro: Haskell Laboratory Report No. 190 83; MR No. 4581 067. (Unpublished study received Oct 26, 1983 under 352 326; submitted by E. I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL: 251571 B)

00137152 McCooey, K. (1983) CHO/ HGPRT Assay for Gene Mutation: [Linuron]: Haskell Laboratory Report No. 540 83; MR No. 4581 067. (Unpublished study received Jan 12, 1984 under 352 326; submitted by E. I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL: 252172 A)

00137153 Farrow, M., et al. (1983) In vivo Bone Marrow Chromosome Study in Rats: [H# 14,703]: HLA Project Number 201 584. Final rept. (Unpublished study received 30 Jan 12, 1984 under 352 326; prepared by Hazleton Laboratories America, Inc., submitted by E. I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL: 252172 B)

00146071 Pastoor, T. (1984) Multigeneration Reproduction Study in Rats with 3( 3,4 Dichlorophenyl) 1 methoxy 1 methylurea (Lorox, Linuron, INZ 326): Haskell Laboratory Report No. 436 84. Unpublished study prepared by E. I. du Pont de Nemours & Co., Inc. 347 p.

00146489 Carter, L. (1985) Metabolism of Phenyl[ Carbon 14 (UL)] Linuron by Male and Female Rats: Document No. AMR 250 84. Unpublished study prepared by E. I. du Pont de Nemours & C0., Inc. 110 p.

00146868 Schulz, M. (1985) Guinea Pig Maxinization Test Using Linuron Technical: Intox Sample No. 584: Project NO. GRF AT 008. Unpublished study prepared by Intox Laboratories. 19 p.

00153867 Hoberman, A. (1985) Developmental Toxicity Study of INZ 326 Administered Via Gavage to New Zealand White Rabbits: Final Report: Protocol 104 009. Unpublished study prepared by Argus Research Laboratories, Inc. 214 p.

00155168 Holt, D.; Carakostas, M. (1985) Hematologic Values in Rats Fed for 20, 22 or 26 Months with 0,25,125 or 625 ppm INZ 326: Haskell Lab. Rep. No. 760 85; Clinical Pathology Rep. No. 21 85. Unpublished study prepared by Haskell Laboratory. 68 p.

00159846 Pastoor, T. (1985) Cross mating Study in Rats with INZ 326: Report No. 413 85: MR No. 4580 001. Unpublished study prepared by E. I. du Pont de Nemours and Co. 70 p.

00163837 Anderson, J. (1984) Dermal Absorption of Carbon 14 Linuron in the Lorox L Formulation by the Rat: Document No. AMR 259 84. Unpublished study prepared by E. I. du Pont de Nemours & Co., Inc. 29 p.

00164093 Pastoor, T. (1986) Biomedical and Pathological Effects of Linuron on Selected Tissues of Male and Female Rats: Report No. 643 86: MR No. 4580 001. Unpublished study prepared by Haskell Laboratory for Toxicology and Industrial Medicine in cooperation with E. I. du Pont de Nemours and Co. 468 p.

00164117 Carakostas, M. (1986) Evaluation of clinical laboratory data from two year rat study with INZ 326. Central Research and Development Department, Haskell Laboratory for Toxicology and Industrial Medicine. Re evaluation of data from Haskell Laboratory Report number 100 80, with no new laboratory or registrant report or study number provided, August 13, 1986, Unpublished.

40142401 Cater, L. (1985) Metabolism of Phenyl Carbon 14( UL) Linuron by Male and Female Rats: ?Supplement to F : Report No. AMR 250 84. Unpublished study 31 prepared by E. I. du Pont de Nemours & Co. 62 p.

40437201 Christian, M. and Hoberman, A. (1985) Supplement to: Developmental Toxicity Study of INZ 326 Administered via Gavage to New Zealand White Rabbits: Laboratory Project ID: MR 7560 001; HLO 609 85. Unpublished study prepared by Argus Research Laboratories, Inc. 76 p.

40952601 Malley, L. (1988) Chronic Toxicity Study with IN Z326 118: One Year Feeding Study in Dogs: Report No. 181 88; Medical Research Project No. 8031 001. Unpublished study prepared by E. I. du Pont de Nemours and Co., Inc. 660 p 41463401 Mullin, L. (1990) Reproductive and Fertility Effects with INZ326 118 (Linuron) Multigeneration Reproduction Study in Rats: Medical Research Project 511 001: Haskell Laboratory Report 20 90. Unpublished study prepared by E. I. du Pont de Nemours and Co., Haskell Laboratory for Toxicology and Industrial Medicine. 1104 p.

41630101 Cook, J. (1990) Investigation of a Mechanism for Leydig Cell Tumorigenesis by Linuron in Rats: Lab Project Number: 494/ 90. Unpublished study prepared by E. I. du Pont de Nemours & Company Inc. 173 p.

41864701 Stula, E. (1990) Reproductive and Fertility Effects with IN Z326 118 MultiGeneration Reproduction Study in Rats: Revised Supplemental: Lab Project Number: 8511 001: 20 90. Unpublished study prepared by E. I. du Pont de Nemours and Co.

41960001 Hundley, S. (1991) Metabolism of [Phenyl Carbon 14( U)] Linuron by the Laboratory Rat: Lab Project Number: HLR 351 91: 1448 89. Unpublished study prepared by E. I. du Pont de Nemours and Co. 7 p.

42006801 Brown, A. (1991) Supplement No. 1 to: Metabolism of [Phenyl 14 Carbon (U)] Linuron by the Laboratory Rat: Lab Project Number: HLR 351 91: 1448 89. Unpublished study prepared by E. I. du Pont de Nemours and Co., Inc. 67 p.

42849001 Shibata, R. (1992) A Primary Eye Irritation Study of Linuron Technical in the Rabbit: Final Report: Lab Project Number: BOZO/ B 2177: B 2177. Unpublished study prepared by Bozo Research Center Inc. 24 p.

42849002 Allen, D. (1993) Linuron Technical: Primary Skin Irritation Test in the Rabbit: Lab Project Number: 498/ 21. Unpublished study prepared by Safepharm Labs, Ltd. 13 p.

Fed Reg Linuron; Preliminary determination to Conclude the Special Review Notice 53( 159): 31262 (August 17, 1988)

U. S. EPA LINURON  Report of the Hazard identification Assessment Review Committee HED Doc No: 0050286 (November 20, 2001) 32 U. S. EPA LINURON: Report of the FQPA Safety Factor Committee, TXR NO. 0050322 (December 6, 2001) 33 9 APPENDICES Tables for Use in Risk Assessment 34 9.1 Toxicity Profile Summary Tables 9.1.1 Acute Toxicity Table  See Section 4.1 9.1.2 Subchronic, Chronic, and Other Toxicity Table Guideline No./ Study Type MRID No. (year)/ Classification /Doses Results 870.3100 90 Day oral toxicity rat Requirement fulfilled by Chronic rat study870.4100a N/ A 870.3150 90 Day oral toxicity dog Requirement fulfilled by Chronic dog study870.4100b N/ A 870.3200 21/ 28 Day dermal toxicity rabbit No study available N/ A 870.3250 90 Day dermal toxicity No study available N/ A 870.3465 90 Day inhalation toxicity No study available N/ A 870.4100 [83 1( b)] 1 Year Feeding Study  Dog 40952601 (1988)

Acceptable/ Guideline 0, 10, 25, 125, 625 ppm % % : 0, 0.29, 0.79, 4.2, 19 mg/ kg/ day & & : 0, 0.30, 0.77, 3.5, 16 mg/ kg/ day NOAEL= 0.77 mg/ kg/ day LOAEL = 3.5 mg/ kg/ day, based on hematological effects in males and females (increased methemoglobin and sulfhemoglobin levels) Guideline No./ Study Type MRID No. (year)/ Classification /Doses Results 35 870.4100 [83 1( b)] 2 Year Feeding Study  Dog 00018374 (1963)

Unacceptable/ Guideline 0, 25, 125, 625 ppm 0, 0.6, 3.1, 16 mg/ kg/ day (based on standard conversion factor of 0.025 .mg/ kg/ day per ppm) NOAEL= 3.1 mg/ kg/ day LOAEL = 16 mg/ kg/ day, based on mild hemolytic anemia, slightly deceased hemoglobin, hematocrit, and RBC counts 870.4200 [83 2 (b)]

Oncogenicity Study  Mouse 0124195 (1981)

Acceptable/ Guideline 0, 50, 150, and 1500 ppm 0, 8, 23, and 261 mg/ kg/ day in males and 0, 12, 35, and 455 mg/ kg/ day in females NOAEL= 23 mg/ kg/ day LOAEL = 261 mg/ kg/ day, based on microscopic liver changes, methemoglobinemia, and deceased body weight gain throughout the study Histopathology: hepatocytomegaly, hepatocellular cytoplasmic alterations, vacuolation, and necrosis in liver, slightly increased incidence of hemosiderosis in spleens of both sexes; significant increase in hepatocellular adenomas in females 870.4300 [83 5( a)]

Combined Chronic Toxicity/ Carcinogenicity Study  Rat 0029680, 00029679 (1980) 00167411 (1986)

Acceptable/ Guideline 0, 50, 125, 625 ppm 0, 2.1, 5.1, 27 mg/ kg/ day in males and 0, 3.1, 7.8, 48 mg/ kg/ day in females NOAEL= 2.1 mg/ kg/ day LOAEL = 5.1 mg/ kg/ day, based on hematological effects, decreased body weight gains in both sexes, microscopic observations consistent with hemolysis (hemosiderin in Kupffer cells and increased hemosiderosis in bone marrow, spleen, and/ or mesenteric lymph nodes)

Histopathology: Significant (p = 0.004) increase (27%, 5.7% control) in incidence of benign interstitial cell adenomas in testes. Guideline No./ Study Type MRID No. (year)/ Classification /Doses Results 36 870.3700 [83 3( a)]

Developmental Toxicity Study  Rat 00018167 (1979)

Acceptable/ Guideline 0, 50, 125, 625 ppm & & : 0, 5.0, 12, 50 mg/ kg/ day Maternal Systemic NOAEL: 12 mg/ kg/ day LOAEL = 50 mg/ kg/ day, based on decreased maternal body weight (9%) and food consumption (7 8%).

Developmental NOAEL: 12 mg/ kg/ day LOAEL = 50 mg/ kg/ day, based on increased post implantation loss and litters with early resorptions.

870.3700 [83 3( b)]

Developmental Toxicity  Rabbit 00153867 (1985), 40437201( 1985)

Acceptable/ Guideline 0, 5, 25, 100 mg/ kg/ day Maternal Systemic NOAEL= 5 mg/ kg/ day LOAEL = 25 mg/ kg/ day, based on decreased maternal body weight gain.

Developmental NOAEL = 25 mg/ kg/ day LOAEL = 100 mg/ kg/ day, based on alterations of the bones and skull (irregularly shaped fontanelle, hole in parietals, parietals contain intraparietals, and unossified).

870.3800 [83 4]

3 Generation Reproduction  Rat 00146071 (1984) 00155168 (1985)

Acceptable/ Guideline 0, 25, 125, 625 ppm % % : 0, 2, 10 11, 48 50 mg/ kg/ day & & : 0, 2, 9, 44 50 mg/ kg/ day Systemic NOAEL= 2 mg/ kg/ day LOAEL = 9 mg/ kg/ day, based on decreased body weight gains in males and females and anemia in females.

Reproductive NOAEL = 10 mg/ kg/ day LOAEL = 44 mg/ kg/ day based on reduced fertility, decreased pup survival and lower pup body weights.

Offspring NOAEL = 9 mg/ kg/ day LOAEL = 44 mg/ kg/ day, based on decreased pup survival, and lower pup body weights. The offspring toxicity NOAEL is Guideline No./ Study Type MRID No. (year)/ Classification /Doses Results 37 870.3800 [83 4] 2 Generation Reproduction  Rat 41463401 (1990) 41864701 (1991)

Acceptable/ Guideline 0, 12.5, 100, 625 ppm % % : 0, 0.74, 5.8, 36 mg/ kg/ day & & : 0, 0.92, 7.3, 45 mg/ kg/ day, Systemic NOAEL= 0.74 mg/ kg/ day LOAEL = 5.8 mg/ kg/ day, based on decreased body weight gains in males and females in both generations Reproductive NOAEL = 36 mg/ kg/ day LOAEL = not established Offspring NOAEL= 0.74 mg/ kg/ day LOAEL = 5.8 mg/ kg/ day, based on decreased pup survival and lower pup body weights of F1a, b and F2a, b litters 870.7600 (85 2) Dermal Penetration Rat 00163837 (1984)

Acceptable/ Guideline 14 C (2.35 : Ci/ mg) 0.12, 1.00, or 7.4 mg/ 2 in2 2.82, 23.5, or 17.4 : Ci Dermal absorption factor = 16% over 8 to 10 hours. Guideline No./ Study Type MRID No. (year)/ Classification /Doses Results 38 870.7485 (85 1) Metabolism Study Rat 00146489 (1985), 40142401 (1985) 41960001 (1991 42006801 (1991) Linuron (single doses at 24 mg/ kg and 400 mg/ kg) was administered by gavage to male and female rats. The biological half lives ranged from 21 hr in the low dose males to 56 hr in the high dose females. Total recovery of radioactivity was 96% in males and 97% in females, the majority of the administered Clinuron was eliminated in the urine (> 80%) and, to a lesser extent, in the feces (~ 15%). Tissue and organ residues were very low (< l%) at both dose levels, and there was no indication of accumulation or retention of linuron or its metabolites. The major metabolites identified in the urine were hydroxy norlinuron, desmethoxy linuron and norlinuron, and in feces, hydroxy norlinuron, and norlinuron. Neither hydroxy 3,4 dichloroanaline nor 3,4 dichloroanaline were present in any of the samples. Exposure to linuron appeared to induce mixed function oxidative enzymes.

Special Study Leydig cell tumorigenesis in rats 41630101 (1990) Acceptable/ Nonguideline 0 or 200 mg/ kg/ day for 14 days to 32 to 33 and 93 day old rats No treatment related clinical signs of toxicity were observed. Body weight and body weight change were significantly less than controls and decreased accessory sex organ weights for growing and adult rats. Guideline No./ Study Type MRID No. (year)/ Classification /Doses Results 39 0, 0.74, 5.8, 36 mg/ kg/ day in males and 0, 0.92, 7.3, 45 mg/ kg/ day in females F0 and F1 animals from 2 generation reproduction study (41463401), Selected animals from the 2 generation reproduction study were used to evaluate changes in serum hormone levels, accessory sex organ weights. Increased serum luteinizing hormone and estradiol levels were observed in F0 and F1 males. High dose F0 males had decreased absolute epididymides, dorsal lateral prostate, and levator ani muscle weights and increased relative testes, epididymides, and ventral prostate weights. Organ weights were unaffected in the two lower dose groups.

These data support the hypothesis that rats exposed to linuron could develop interstitial hyperplasia and subsequent adenomas (Leydig cell tumors) via a mechanism of sustained hypersecretion of luteinizing hormone induced by the antiandrogenic potential of linuron.

Special Study Cross Mating 00159846 (1985)

Acceptable/ Nonguideline 0, 625 ppm % % : 0, 48 mg/ kg/ day & & : 0, 44 mg/ kg/ day The cross mating results suggest that linuron may cause paternally mediated effects based on decreased fertility and fecundity as well as maternally mediated effects based on decreased pup viability and litter survival.

Special Study Aged male rats 45506501 (1986)

Acceptable/ Nonguideline 0, 625 ppm 0, 22 mg/ kg/ day Linuron induced hyperplasia and adenomas of the testes in aged rats. In addition, life time feeding was not necessary to induce oncogenic responses in this tissue. Guideline No./ Study Type MRID No. (year)/ Classification /Doses Results 40 Special Study Biochemical and Histopathological effects 164093 (1986)

Acceptable/ Nonguideline 0, 12.5, 100, 625 ppm % % : 0, 0.75, 4.1, 22 mg/ kg/ day & & : 0, 1.1, 6.1, 37 mg/ kg/ day The biochemical and histopathological data presented in this report suggest that linuron may affect testosterone metabolism in horse testicular microsomes for a range of concentrations which overlap the dose levels given rats chronically. However, the net effect of these enzyme changes and the relevance to the rat in vivo are uncertain. Evidence in young and old rats exposed repeatedly (3 7x) or for 11 or 19 months suggests that Leydig cell incubates are differentially altered in their sensitivity to LH. Microscopic lesions in the testes and cervix have been confirmed in other studies. 41 9.2 Summary of Toxicological Dose and Endpoints for Linuron for Use in Human Risk Assessment 42 Exposure Scenario Dose Used in Risk Assessment, UF FQPA SF and Endpoint for Risk Assessment Study and Toxicological Effects Acute Dietary females 13 50 years of age NOAEL = 12 UF = 100 Acute RfD = 0.12 mg/ kg/ day FQPA SF = 3 aPAD = acute RfD FQPA SF = 0.04 mg/ kg/ day Prenatal Oral Developmental / Rat LOAEL = 50 mg/ kg/ day based on increased post implantation loss and fetal/ litter resorptions.

Acute Dietary general population including infants and children N/ A N/ A No appropriate effects attributed to a single exposure was identified.

Chronic Dietary all populations NOAEL= 0.77 mg/ kg/ day UF = 100 Chronic RfD = 0.0077 mg/ kg/ day FQPA SF = 10 cPAD = chr RfD FQPA SF = 0.00077 mg/ kg/ day Chronic Feeding Study  Dog LOAEL = 4.2 mg/ kg/ day in males and 3.5 mg/ kg/ day in females based on increased met and sulfhemoglobin levels.

Short Term Oral (1 7 days)

(Residential) NOAEL= 5.8 mg/ kg/ day LOC for MOE = 1000 (Residential, includes the FQPA SF) 2 Generation Reproduction Study/ Rat LOAEL = 36 mg/ kg/ day based on statistically and biologically significant decrease in premating body weights in F0 and F1 animals IntermediateTerm Oral (1 week  several months)

(Residential) NOAEL= 0.77 mg/ kg/ day LOC for MOE = 1000 (Residential, includes the FQPA SF) Chronic Feeding Study  Dog LOAEL = 4.2 mg/ kg/ day in males and 3.5 mg/ kg/ day in females based on increased met and sulfhemoglobin levels.

Short Term Dermal (1 30 days)

(Occupational/ Residential) Oral NOAEL= 5.8 mg/ kg/ day dermal absorption rate = 16% LOC for MOE = 100 (Occupational)

LOC for MOE = 1000 (Residential, includes the FQPA SF) 2 Generation Reproduction Study/ Rat LOAEL = 36 mg/ kg/ day based on statistically and biologically significant decrease in premating body weights in F0 and F1 animals Exposure Scenario Dose Used in Risk Assessment, UF FQPA SF and Endpoint for Risk Assessment Study and Toxicological Effects 43 IntermediateTerm Dermal (1  6 months)

(Occupational/ Residential) Oral NOAEL= 0.77 mg/ kg/ day dermal absorption rate = 16% LOC for MOE = 100 (Occupational)

LOC for MOE = 1000 (Residential, includes the FQPA SF) Chronic Feeding Study  Dog LOAEL = 4.2 mg/ kg/ day in males and 3.5 mg/ kg/ day in females based on increased met and sulfhemoglobin levels after 3 and 6 months of treatment Long Term Dermal (Longer than 6 months) (Occupational/ Residential) Oral NOAEL= 0.77 mg/ kg/ day dermal absorption rate = 16% LOC for MOE = 100 (Occupational)

LOC for MOE = 1000 (Residential, includes the FQPA SF) Chronic Feeding Study  Dog LOAEL = 4.2 mg/ kg/ day in males and 3.5 mg/ kg/ day in females based on increased met and sulfhemoglobin levels.

Short Term Inhalation (1 30 days)

(Occupational/ Residential) Oral NOAEL= 5.8 mg/ kg/ day (inhalation absorption rate = 100% LOC for MOE = 1000 (Residential, includes the FQPA SF) 2 Generation Reproduction Study/ Rat LOAEL = 36 mg/ kg/ day based on statistically and biologically significant decrease in premating body weights in F0 and F1 animals IntermediateTerm Inhalation (1 to 6 months)

(Occupational/ Residential) Oral NOAEL= 0.77 mg/ kg/ day (inhalation absorption rate = 100% LOC for MOE =1000 (Residential, includes the FQPA SF) Chronic Feeding Study  Dog LOAEL = 4.2 mg/ kg/ day in males and 3.5 mg/ kg/ day in females based on increased met and sulfhemoglobin levels.

Long Term Inhalation (Longer than 6 months)

(Occupational/ Residential) Oral NOAEL= 0.77 mg/ kg/ day inhalation absorption rate = 100% LOC for MOE = 100 (Occupational)

LOC for MOE = 1000 (Residential, includes the FQPA SF) Chronic Feeding Study  Dog LOAEL = 4.2 mg/ kg/ day in males and 3.5 mg/ kg/ day in females based on increased met and sulfhemoglobin levels. Exposure Scenario Dose Used in Risk Assessment, UF FQPA SF and Endpoint for Risk Assessment Study and Toxicological Effects 44 Cancer (oral, dermal, inhalation) Group C carcinogen Does not require quantification of human cancer risk Based on a dose related increase in interstitial cell hyperplasia and adenomas in a two year rat feeding study and hepatocellular tumors that appeared in low dose male and high dose female mice in a two year feeding study 1 UF = uncertainty factor, FQPA SF = FQPA safety factor, NOAEL = no observed adverse effect level, LOAEL = lowest observed adverse effect level, PAD = population adjusted dose (a = acute, c = chronic) RfD = reference dose, LOC = level of concern, MOE = margin of exposure