10.4081/btvb.2022.21
This narrative review article summarizes the strong available evidence that casually links indoor and outdoor air pollution to cardiovascular disease. It also discusses as a possible approach to mitigate this ubiquitous risk factor the use in the household of ornamental potted plants, and their variable degree of effectiveness for the removal of different indoor pollutants such as volatile organic compounds (formaldehyde, benzene, toluene, xylene). Thus, the choice of the plants should be tailored to the types and concentrations of the pollutants present in each household. Outdoor air is less polluted than indoor air in terms of concentrations of the gaseous (NO2) and particulate components (PM10, PM2.5, PM0.1), but it does hamper to a higher extent health because a large fraction of the population is inevitably exposed at the time of breezing. Being cognizant of the difficulties currently encountered in the attempts to mitigate the major sources of ambient air pollution (vehicle traffic and domestic heating) a strategy based upon a massive increase of green spaces in urban areas has been shown not only to positively mitigate air pollution but also improve life expectancy, general health and resilience.
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2785-5309
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en
Pier Mannuccio Mannucci
https://creativecommons.org/licenses/by-nc/4.0
Bleeding, Thrombosis and Vascular Biology
Air quality guidelines
An ecological alliance against air pollution and cardiovascular disease
Text.Serial.Journal
https://www.btvb.org/btvb
1
Narrative Reviews
2022-03-22
2022-02-23
2022-03-22
2022-05-02
Bleed Thromb Vascul Biol
Pier Mannuccio Mannucci
2022/03/22
10.4081/btvb.2022.21
Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, IRCCS Ca’ Granda Ospedale Maggiore Policlinico Foundation, Milan
2785-5309
1
Air quality guidelines
en
Nieuwenhuijsen MJ, Khreis H. Car free cities: pathway to healthy urban living. Environ Int 2016;94:251-62.
An ecological alliance against air pollution and cardiovascular disease
https://www.btvb.org/btvb/article/download/21/10
1
                                                                                                        NARRATIVE REVIEW

An ecological alliance against air pollution and cardiovascular disease
Pier Mannuccio Mannucci

Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, IRCCS Ca’ Granda Ospedale Maggiore Policlinico Foundation, Milan,
Italy



ABSTRACT
    This narrative review article summarizes the strong available evidence that casually links indoor and outdoor air pollution to cardio-
vascular disease. It also discusses as a possible approach to mitigate this ubiquitous risk factor the use in the household of ornamental
potted plants, and their variable degree of effectiveness for the removal of different indoor pollutants such as volatile organic compounds
(formaldehyde, benzene, toluene, xylene). Thus, the choice of the plants should be tailored to the types and concentrations of the pollutants
present in each household. Outdoor air is less polluted than indoor air in terms of concentrations of the gaseous (NO2) and particulate
components (PM10, PM2.5, PM0.1), but it does hamper to a higher extent health because a large fraction of the population is inevitably ex-
posed at the time of breezing. Being cognizant of the difficulties currently encountered in the attempts to mitigate the major sources of
ambient air pollution (vehicle traffic and domestic heating) a strategy based upon a massive increase of green spaces in urban areas has
been shown not only to positively mitigate air pollution but also improve life expectancy, general health and resilience.




                                                                                             ly
                                                                            fortnight hospital admissions for pneumonia, asthma and




                                                                                     on
INTRODUCTION                                                                bronchitis progressively increased and peaked in sever-
    The first cogent example of the ominous effects of                      ity to reach 12.000 fatalities. This number is impressive



                                                                                e
bad air on human health dates back to the last few                          and only marginally lower than that of the 30.000 deaths
months of 1952. In the metropolitan area of London, the
combined effect of the unusual absence of rain and wind,
                                                                           us
                                                                            due to the London bombing by the Luftwaffe, thus ex-
                                                                            plaining the deep emotional reactions of Londoners who
coupled with high atmospheric pressure and very low                         were just starting to recover from the mayhem of the sec-
                                                                           al
ambient temperatures, led to very intensive domestic and                    ond world war.
public heating mainly based upon the use of solid fuels                         This historical preamble is meant to emphasize that
                                                        ci


such as coal of poor quality and rich in sulfur. The great                  air pollution was initially thought to target the lungs and
                                                      er



London smog lasted only for the first 10 days of Decem-                     respiratory airways and that the excess deaths documented
ber until the arrival from the Atlantic of wind and rain                    during and soon after the great London smog were due to
                                                     m




that washed away the smog. However, during the next                         pneumonia and other acute respiratory illness. It is only
                                          om




                                                                            in this century that it was unequivocally understood that
                                                                            the short- and long-term human exposure to particulate
                                                                            and gaseous pollutants contained in ambient air, such as
                                   -c




  Correspondence: Pier Mannuccio Mannucci, Angelo Bianchi
  Bonomi Hemophilia and Thrombosis Center, IRCCS Ca’ Granda
                                                                            PM2.5, PM10, PM0.1 and nitric dioxide (NO2), are also risk
                                                                            factors for cardiovascular morbidity and mortality.1-5
                          on




  Ospedale Maggiore Policlinico Foundation, Via Pace 9, 20122
  Milan, Italy.                                                                 In order to provide upfront in this essay cogent in-
  Tel.: +39.02.55035421                                                     formation on the magnitude of the risk of cardiovascular
                    N




  E-mail: piermannuccio.mannucci@policlinico.mi.it
                                                                            disease and ultimately suggest some strategies for miti-
  Key words: Outdoor pollutants, Indoor pollutants, Green space,            gation of the risk associated with air pollution and its
  Organic volatile compounds, Air quality guidelines.                       consequences at the individual as well as community
  Conflict of interest: The author declares no potential conflict of in-
                                                                            levels, it is a fact and deed that the World Health Organ-
  terest.                                                                   ization (WHO) and the Global Burden of Disease (GBD)
                                                                            study had concordantly estimated that air pollution is
  Funding: None.                                                            globally the fourth leading cause of morbidity and mor-
  Received for publication: 23 February 2022.                               tality, being casually responsible each year for 7 million
  Accepted for publication: 23 February 2022.                               excess deaths, approximately half due to ambient (out-
                                                                            door) pollution and the remaining half to household (in-
  This work is licensed under a Creative Commons Attribution Non-
                                                                            door) pollution.6,7 According to recent estimates based
  Commercial 4.0 License (CC BY-NC 4.0).
                                                                            upon more accurate measures of exposure and new ex-
  ©
   Copyright: the Author(s), 2022                                           posure-response functions, the forementioned dramatic
  Licensee PAGEPress, Italy                                                 number of avoidable deaths underestimates the real bur-
  Bleeding, Thrombosis and Vascular Biology 2022; 1:21
  doi:10.4081/btvb.2022.21
                                                                            den, that is above 9 millions.5,8,9
                                                                                Pertaining to the non-communicable diseases globally

                                              Bleeding, Thrombosis and Vascular Biology 2022; 1:21
20                                                       P.M. Mannucci




association with air pollution, cardiovascular diseases ac-       door pollutants such as particulate matter, benzene and
count for 5.1 million annual deaths, many more than those         formaldehyde, but also of carcinogen compounds such as
due to chronic pulmonary disease (1.2 million), cancer            benzo a-pyrene. Any type of fire is a source of pollution,
(more than 700.000), diabetes and chronic kidney disease          particularly when heating and cooking make use of fire-
(more than 500.000).10 Within the category of                     places and stoves that burn biomass such as wood and pel-
atherothrombotic cardiovascular diseases, ischemic heart          lets. Computers, printers and copy machines are sources
disease contributes with more than 2.6 million annual             of such carcinogen organic volatile compounds as xylene
deaths, ischemic stroke with nearly 2.3 millions and hy-          and toluene. Moreover, human beings living in closed en-
pertension with 170.000.10 Pertaining to the role of the dif-     vironments produce beside CO2 such bioeffluents as ace-
ferent components of air pollution, PM2.5 is regarded as          tone, methane and ammonia. Air purifiers with filters of
the main culprit, both for short-term exposure (within            high quality and efficiency are useful but very expensive
hours to days) and long-term exposure (years) to this fine        at the time being. Airing the ambients, particularly those
particulate matter, that is also a proxy of primary and sec-      more densely inhabited, is an obvious and inexpensive ap-
ondary gaseous pollutants such as nitric dioxide and              proach to limit the indoor concentrations of pollutants but
ozone.10 A large meta-analysis of 35 studies demonstrated         open windows inevitably cause the introduction into the
that a daily increase of as little as 10 micrograms per cubic     household of outdoor pollution. In dense urban areas a
milliliter of PM2.5 is associated with a 10% increase of          meaningful strategy is to choose ventilate the house in the




                                                                                            ly
cardiovascular mortality due to ischemic heart disease,           early hours of the morning and late afternoon, at a time




                                                                                   on
stroke but also congestive heart failure, atrial fibrillation     when outdoor pollutants due to motor vehicle traffic are
and ventricular arrhythmias,11 including sudden deaths            in smaller concentrations.
due to cardiac arrest.12                                              Tobacco smoke, fires and human effluents are not the



                                                                              e
    The mechanistic transition of pollution exposure to-          only sources of indoor pollution. Products commonly em-
wards these cardiovascular outcomes occurs in different
steps, initiating with generalized oxidative inflammation
                                                                         us
                                                                  ployed for house furnishing and cleaning such as volatile
                                                                  detergents, covering plastic glues, fitted carpets and
and activation of neuro reflex arcs.13-15 The subsequent ef-      wooden panels often contain and release in the ambient
                                                                 al
fector pathways act through such mechanistic intermedi-           such carcinogens as formaldehyde and benzene. More-
ates as autonomic dysfunction and endocrine disruption,
                                                      ci

                                                                  over, organic volatile compounds are also released by fur-
that in turn lead endothelial perturbation, plaque instabil-      niture, paints and toys.
                                                    er



ity, hypercoagulability and hypertension, ultimately re-              It is refreshing to realize that indoor pollution can be
sulting in the forementioned cardiovascular events.13-15
                                                   m




                                                                  mitigated by plants. In 2017 the NASA tested different or-
    With this background on the large dimension of the            namental potted plants for their properties to remove
                                          om




damage of air pollution on human health, explained by a           harmful agents such as formaldehyde, benzene, xylene
high population-attributable fraction of this risk factor and     and toluene. The study led to a 70% reduction in the of-
its inescapability with breezing, what can be done to             fices of this agency of the indoor concentrations of
                                     -c




tackle this problem at the level of the community but also        volatile organic compounds by using the most efficient
of the individual? The latter is able to play a key role          house plants, such as bamboo palm, English ivy, weeping
                             on




mainly in the mitigation of indoor air pollution, whereas         fig, gerbera, dracena and others.17 For instance, the remov-
actions from the community and its governmental repre-            ing capacity of the weeping fig (Ficus benjamina) is of
                         N




sentatives are essential in the context of the formidable         20 g/h for formaldehyde, 7 g/h for benzene, 19 g/h ace-
attempts to mitigate ambient air pollution and thereby            tone and 5 g/h ammonia.18 So, the ecological transition
manage to decrease the associated risk of cardiovascular          that stems from these findings is that it is possible to clean
morbidity and mortality.16                                        houses and offices with natural weapons and to use orna-
                                                                  mental houseplants as a sort of green liver.18,19
                                                                      On the whole, the take-home messages for those who
MITIGATION OF INDOOR POLLUTION                                    aim to reduce indoor pollution is to strictly avoid both
    It is generally believed that this problem afflicts al-       active and passive smoking, skip fireplaces, increase
most exclusively low-income countries that make an                house ventilation in the most suitable hours of the day
abundant use in the house of biomass or fossil fuels for          and choose furniture, toys, tools and paints with low am-
cooking and heating. Even though, this is indeed a gigan-         bient impact and emission of carcinogen organic volatile
tic problem there is less awareness that indoor pollution         compounds. In addition, one should clean the house with
is a cogent issue also in high income countries, consider-        natural detergents and use as green liver house plants,
ing that human beings spend at least 70-90% of their lives        chosen on the basis of their varied ability to remove
indoor doing an array of activities. Active and passive to-       those pollutants that are more prominent in each indoor
bacco smoking is a prominent and avoidable source of in-          context.18,19

                                     Bleeding, Thrombosis and Vascular Biology 2022; 1:21
                                 An ecological alliance against air pollution and cardiovascular disease                          21



                                                                        areas, particularly those in the Po plain in Italy and East-
CONTROL OF OUTDOOR, AMBIENT                                             ern Europe (Poland, but also Romania and Bulgaria) is
AIR POLLUTION                                                           particularly gloomy, considering that WHO released in
    At global, national and urban scales the main sources               2021 new and much more stringent air quality guidelines
of pollutants in the ambient air are automobile traffic, do-            to be attained in order to truly preserve human health.
mestic and office heating, industrial and shipping activi-              Table 1 shows the WHO newly recommended daily and
ties, power stations and intensive farming. The relative                annual ceilings and also shows the huge gaps between
burden of each source depends on the site of human ex-                  them, those of EPA (that is however updating and lower-
posure, but urban areas are definitely the most polluted,               ing them soon) and of the European Union that, released
not only in high income countries but also in middle- low-              as early as in 2008, are unfortunately still not updated de-
income countries. It is difficult to establish with accuracy            spite their poor adequacy to preserve the health of Euro-
which of the major sources of outdoor pollution carries                 pean citizens.22
the greatest burden in terms of related disease occurrence.                 Standards and guidelines represent a target, but their
Diesel motor engines are considered the major contribu-                 actual implementation is a formidable task. In general,
tors to the air concentrations of NO2 but also of pollutants            there is tendency to blame the road traffic of motor vehi-
such as particulate matter and ozone that form secondarily              cles using fossil fuels, and thus to worship electric engines
in the atmosphere. However, any fossil fuel is a source                 as the optimal solution. Accordingly, a few countries, in




                                                                                          ly
of pollution, and there is mounting evidence that also al-              Europe and elsewhere, have set a deadline for the complete




                                                                                  on
legedly clean engines using super unleaded gasoline are                 ban of internal combustion engines. The implementation
an important source of ultrafine particulate matter (PMQ.1,             of this goal without significant economic and employment
more and more shown to be a most dangerous pollutant                    problems is a formidable task, in Italy and other countries.



                                                                             e
for human health and the cardiovascular system.20,21                    Moreover, the scourge of the coronavirus pandemic that
    Another important point to be emphasized in the con-
                                                                      usobliged to stop motor traffic in many urban areas of the
text of the potential approaches towards mitigation of am-              world has shown as a bad teacher that automobile traffic
                                                                        is not necessarily the main culprit. In China, where the
                                                                al
bient air pollution is the threshold of each pollutant that
should not be exceeded for the preservation of human                    lockdown was strictly implemented in the winter of 2020
                                                  ci


health, using as references guidelines or standards set by              with the involvement of the army, air pollution and partic-
                                                                        ularly NO2 concentrations were dramatically reduced in
                                                er


WHO and various national or multinational organizations.
For instance, the USA Environmental Protection Agency                   the central and southern urban areas, but not in Beijing and
                                               m




(EPA) recommends ceilings not to be exceeded daily and                  other northern cities, where heating of the domestic and
annually and air quality guidelines have been set also by               public ambients could not be stopped in the cold months.23
                                        om




the European Environmental Agency (Table 1). Pertaining                 A similar pattern was observed in the Italian region of
to gaseous components such as NO2 and particulate matter                Lombardy, the first in Europe to be dramatically hit by the
such as PM2.5 and PM10, the ceilings recommended by                     SARS-CoV-2 pandemic in the early months of 2020. Thus,
                               -c




EPA are much more stringent (lower) than those of the                   domestic and office heating is an important cause of the
                                                                        burden of ambient air pollution, even though the propor-
                        on




European Agency. Nevertheless, a report on air quality re-
leased in 2016 by the European Agency found that at least               tion between this component and that due motor vehicle
                                                                        traffic varies depending on the geographic locations and
                  N




15% of the people living in urban areas of the continent
exceed even the scarcely demanding ceilings of the Eu-                  other characteristics of urban areas.
ropean guidelines, let alone those of WHO with a 90%                        Putting aside as being currently unrealistic the myth
exceeding rate! The current situation of several urban                  of deep decarbonization and the global implementation of
                                                                        renewable energy sources, an ecological approach to a
                                                                        cleaner air based upon more greenness is being imple-
                                                                        mented in highly polluted countries such as China and
Table 1. Comparison of the ceilings of mean annual
                                                                        India, that are aggressively developing nationwide pro-
concentrations (µg/mm3) of the main ambient air pollutants
according to the current directions for ambient air quality of the      grams of intensive forestation.24 Greenness reduces air
European Union (EU), USA Environment Protection Agency                  and noise pollution and has additional health benefits by
(EPA) and World Health Organization (WHO).                              promoting physical activities such as walking, cycling and
                                                                        running that ultimately help to mitigate the adverse effects
Pollutant          EU             EPA             WHO
                                                                        of pollution on cardiovascular morbidity and mortality.25-
PM10               40               -               15                  27
                                                                           Furthermore, a prospective cohort study carried out in
PM2.5              25              12                5
                                                                        the USA by the Harvard School of Public Health on 108
NO2                40              30               10                  nurses showed that those with residence in areas with
Ozone             120              100              60                  higher greenness have a significantly lower all-cause mor-

                                         Bleeding, Thrombosis and Vascular Biology 2022; 1:21
22                                                          P.M. Mannucci




tality than those with residence in the so-called grey areas          outdoor pollution emphasized in this essay. Other benefits
with little or no green space.28 The most plausible mech-             of green space are stress reduction, more physical activity,
anisms for these positive effects of green space are the              more social interactions and lower exposure to other en-
ecosystem services offered by trees, that remove signifi-             vironmental risk factors for health and wellbeing such
cant amount of particulate and gaseous pollutants. For in-            noise, heat and humidity.25,26 About half of the premature
stance, a study carried out in 55 urban areas of the USA              deaths attributed to exposure to indoor and outdoor pol-
showed that 711 tons of pollutants (ozone, PM, NO2) were              lution occur in fragile individuals (children, older and
removed annually, with a monetary value of 3.8 billion                poor people, pregnant women) and in those living in low-
dollars owing to health fostering and illness avoidance.29            income countries. We hope that this essay will help to
On behalf of the Ecological Services of Urban Forest,                 convince the readership of this new journal that more trees
Barò et al. conducted in Barcelona a study that measured              and forests are able to restore clean air much more easily
the number of pollutants removed by urban green and cal-              than the currently too difficult and demanding actions on
culated the corresponding monetary value. They found                  heating and traffic.
that 306 tons of air pollutants are annually removed and
that the corresponding monetary values are 1.15 million
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                                                 er
                                                m
                                       om
                                 -c
                         on
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