Air pollution, both indoor and outdoor, is a significant cause of health problems worldwide. Urban and rural outdoor environments contain infections, allergens, irritants and chemical toxins that can reduce the quality of life and cause disease. Inhaled air pollution is directed at the the nose, throat and lungs. The exposed airway allows hazardous pollutants to enter the body and all tissues are ultimately exposed.
Air pollution was first noticed as problem of city dwellers, poisoning themselves, but more recently, air pollution is acknowledged as a problem of global significance. The tolerance for environmental destruction is ancient and human history is littered with civilizations that failed because humans exploited natural resources and spoiled their own nest. Humans adapt easily to deteriorating conditions and will persist in following daily routines even when air pollution is severe, traffic is congested, water and food supplies are at risk, and social order is unstable.
Spector reported the findings of Yale and Columbia University researchers who created the Environmental Performance Index—a biennial ranking of how well 180 countries protect the health of their populations and ecosystems. The EPI reported that 3.5 billion people, half of humankind, live in areas where air pollution exceeds the safe level designated by the World Health Organization. Air pollution has gotten worse and more people are dying from air pollution. (Julian Spector . Half the World Still Breathes Polluted Air. CityLab - January 30, 2016)
Michael Brauer, a professor at the University of British Columbia’s School of Population and Public Health in Vancouver, Canada stated:” Air pollution is the fourth highest risk factor for death globally and by far the leading environmental risk factor for disease. Reducing air pollution is an incredibly efficient way to improve the health of a population.“The findings of the UBC group were discussed Feb 2016 at the annual meeting of the American Association for the Advancement of Science, in Washington.
Fine-particulate air pollution is known to contribute to cardiovascular and lung disease, increasing the risk of heart attacks and a heart-related death. Researchers at Brigham Young University and Harvard School of Public Health compared changes in air pollution from 1980 to 2000 with residents’ life expectancies, They concluded that a reduction in air pollutants in 51 U.S. cities between 1980 and 2000 added an average of five months to life expectancy. Residents in cities that made the most significant improvements in air quality, such as Pittsburgh, PA, lived almost 10 months longer. For every microgram per cubic meter decrease in fine-particulate air pollution, life expectancies rose by more than seven months.
Airborne chemicals contaminate food and water. Airborne chemicals are ingested; they collect in the nose and throat and are swallowed, often in mucus that attempts to protect exposed surfaces. Airborne chemicals entering the digestive system include well-known toxins such as pesticides, organophosphate, PCBs, dioxin, arsenic, cadmium, lead, and mercury. In addition occupational exposures to airborne pathogens can be intense and can cause cancer.
Air pollution is associated with increased hospital admissions for cardiovascular diseases with increases in acute morbidity and mortality. D'Ippoliti et al studied 6531 patients in Rome who were hospitalized for acute myocardial infarction from January 1995 to June 1997. Air pollution data were taken from 5 city monitors. Positive associations were found for total suspended particulates, NO2 and CO. The strongest and most consistent effect was found for total suspended particulates.
Increases in fine particulate matter air pollution increase the risk for myocardial infarctions, strokes, and heart failure. For example, particle deposition in the lungs activates the sympathetic nervous system and triggers the release of systemic pro-inflammatory responses. Brook and Rajagopalanb stated: "Higher circulating levels of inflammatory cytokines cause vascular endothelial dysfunction and activation of vasoconstrictive pathways while blunting vasodilator capacity. At the molecular level, the generation of oxidative stress with the consequent up-regulation of redox sensitive pathways appears to be a common mechanism of these pro-hypertensive responses. Due to the ubiquitous, continuous and often involuntary nature of exposure, airborne fine particles may be an important and under-appreciated worldwide environmental risk factor for increased arterial BP.
VovKlot et al conducted a multicenter study involving 22,006 survivors of a first myocardial infarction in European cities. Air concentrations of nitrogen dioxide, carbon monoxide, ozone, and particles (PM10) were measured: 6655 cardiac readmissions were observed. Cardiac readmissions increased in association with same-day concentrations of PM10. Effects of similar strength were observed for carbon monoxide, nitrogen dioxide and ozone, They concluded that air pollution is associated with increased risk of hospital cardiac readmissions of myocardial infarction survivors in 5 European cities.
Simkhovich et et al confirmed that epidemiologic studies show that increased levels of air pollutants are positively associated with cardiovascular morbidity and mortality. They stated: "Inhalation of air pollutants affects heart rate, heart rate variability, blood pressure, vascular tone, blood coagulability, and the progression of atherosclerosis. Major mechanisms of inhalation-mediated cardiovascular toxicity include activation of pro-inflammatory pathways and generation of reactive oxygen species. Although most studies focus on the influence of systemic effects, recent studies indicate that ultrafine particles may be translocated into the circulation and directly transported to the vasculature and heart where they can induce cardiac arrhythmias and decrease cardiac contractility and coronary flow."
Endocrine and Reproductive Systems (Damstra)
Environmental toxins can interfere with the endocrine (hormone- producing) and reproductive systems to a degree that merits public concern. Harmful effects on these crucial body systems have been observed in people, farm animals, and wildlife. A few studies have noted that sperm counts have decreased and there is an increase in congenital and developmental abnormalities of the genitalia and testicular cancer. The incidence of endometriosis appears to be increasing, and the age of its onset may be decreasing.
Breast cancer increased at the rate of approximately 1 percent per year for the past 50 years. It has been shown that several chemicals present in environmental pollution have the capacity to act as carcinogens and as hormones. When these chemicals are taken into the body through air pollution, they can mimic the effects of the body's natural hormones and disrupt a number of important biological processes. Environmental pollutants that can mimic the hormone estrogen include DDT, DDE, kepone, heptachlor, PCBs, dioxin, and break-down products of detergents.
These compounds can be carried for long distances through air pollution and then deposited into soil and water, and eventually into the food chain. These hormonally active chemicals have been shown to disrupt the reproductive development of fish and wildlife, often resulting in infertility due to feminization of males or masculinization of females. Offspring may be permanently affected by exposure to these chemicals while they are still in the mother's uterus. For example, we know that exposure to the synthetic estrogen Diethylstilbestrol (DES) produces severe reproductive effects in both the sons and daughters of DES-taking mothers. Prenatal exposure to DES is associated with vaginal cancer, peri-ovarian cysts, abnormalities of the uterus, and reproductive dysfunction in the female offspring. Males are reported to develop testicular abnormalities and undescended testes. In addition, exposure to DDT and PCBs may be associated with breast cancer.
Dioxin, one of the most toxic chemicals in the environment, is capable of blocking estrogen action, lowering levels of androgens (male hormones), and affecting the amount of thyroid hormones produced. It can also affect insulin levels and the amount of glucocorticoid secreted by the adrenals. It has also been implicated as a cause for endometriosis. Exposure of pregnant animals to very low levels of dioxin can damage the reproductive system of the offspring, resulting in a decreased sperm count and altered mating behavior. Many pollutants mimic estrogen and may be responsible for breast and uterine tumors. -- Kathy Bryant, LLB, American College of Obstetrics and Gynecology
Air Pollution and the Musculoskeletal System (McGowan)
Bone provides structural support for the body and plays an important role as a reservoir for vital minerals. These tissues are constantly absorbing and releasing chemicals that circulate through the blood. Bone is continuously remodeling itself (breaking down and reforming), and it is this characteristic that makes bone a prime target for pollutants. And later, if pollutants are stored in bone, the bone becomes a source of toxic substances. For example, lead is readily taken up by bone and incorporated into its building blocks. This incorporation can be initially protective for the rest of the body when there is an acute exposure, but eventually the lead is released slowly back into the body. Toxic substances can therefore remain a threat to health for decades, and may be particularly hazardous when they are released into the general blood circulation at critical periods of life (e.g., pregnancy, lactation, menopause, or advanced age). Bone loss is accelerated during menopause at which time bone mass may decrease by 2% to 3% per year for several years. During this period, stored toxins may be released and cause damage to the nervous system and other organs. This problem is worsened when an individual's diet is calcium- deficient because this deficiency accelerates mineral release from bone. Lead is the most serious of several hazardous pollutants that affect bone, in countries that continue to use leaded gasolines. High levels of lead and cadmium have been measured in cigarette smoke and may contribute significantly to the total lead body burden. Children are especially vulnerable to lead poisoning and must be protected from lead exposure in order to prevent the consequences of nervous system dysfunction. Lead uptake in children has also been shown to decrease skeletal growth, apparently by specifically inhibiting genetic expression in bone cells. Bone cells exposed to lead fail to produce key proteins that are necessary for bone growth.
Air Pollution and the Digestive System (Bailey)
Air pollution is a less significant source of hazardous environmental chemicals in the gastrointestinal (GI) tract than is the ingestion of contaminated food and water (which may have been contaminated by air pollution). Direct exposure of the digestive system to environmental chemicals usually occurs via the mouth through swallowing contaminated material, but it may also result from swallowing mucus that contains inhaled toxicants. Environmental chemicals entering the digestive system include those associated with contaminated food (e.g., pesticides, organophosphate, PCBs, dioxin, arsenic, cadmium, lead, and mercury), and others usually associated with occupational exposure (e.g., asbestos, acrylonitrile, butylate hydroxytoluene, and polycyclic hydrocarbons). These chemicals have been reported to cause gastritis, esophageal and gastric necrosis, and gastrointestinal cancer.
Air Pollution and Women's Health (Bryant)
The Society for the Advancement of Women's Health Research at its first national conference proposed the following:
1. Women's health is at risk because little attention has been paid to understanding and preventing the harmful effects of environmental toxins on women;
2.While more research is needed, many diseases affecting women appear to have an environmental link;
3.Due to women's unique physiology, they may respond differently than men to environmental toxin exposure; and
4.Current federal government risk assessment policy fails to fully consider women's health concerns when setting safe exposure levels. It is proposed that an aggressive research commitment is necessary to identify and understand the unique way environmental toxins in the air interact with women's bodies. For example, many chemical pollutants have the potential to produce estrogenic effects when absorbed into the body, and may be a factor in breast cancer development.
Organochlorines such as DDT, PCBs, and polycyclic aromatic hydrocarbon (PAH) petroleum byproducts have been shown in animal studies to mimic estrogen, and many have induced or promoted mammary tumors in rats. These chemicals can be inhaled as air pollutants resulting from industrial manufacturing, energy production, and traffic exhaust. Many of these toxins are stored in fat and may reside in the body for long periods of time. Storage of toxins in fat is a problem of greater importance in women because of their higher percent of body fat and the hormonal changes that occur during pregnancy, lactation, and menopause, which can result in mobilizing internal stores of pollutants many years after the initial exposure. Exposure to occupational chemicals may affect reproductive capacity adversely in the form of reduced fertility, spontaneous abortion, low birth weight, birth defects and developmental disabilities. For example, exposure to inhalational anesthetic agents has been associated with adverse pregnancy outcomes in female operating room personnel. Currently, only 30 to 40 chemical, physiologic, and biologic agents have been identified as human teratogens because of the difficulty in proving a causal association, but the Society believes this number is probably well below the final total that will be found. Every year, approximately 1,000 new chemicals are developed and added to the 70,000 unique chemicals, and 9 million mixtures, formulations, and blends of chemicals already in commercial use. Few of these chemicals have been adequately assessed for their potential toxicity, either individually or in conjunction with other chemicals. A study by the National Academy of Sciences has been proposed in Congress to determine the science base and research needed to ensure that environmental standards protect the health of men and women. Women have more chronic illness than men -- partly because they live longer, partly because of the storage of toxins in fat and bone. -- Joan McGowan, PhD, National Institute of Arthritis and Musculoskeletal and Skin Diseases
Air Pollution Hazards to Children (Etzel)
Children are more vulnerable to airborne pollution for many reasons, including the fact that their airways are narrower than adults, they have markedly increased needs for oxygen relative to their size, they breathe more rapidly and inhale more pollutants per pound of body weight, and they spend more time engaged in vigorous outdoor activities than adults. While levels of outdoor pollutants decreased substantially after passage of the Clean Air Act, levels of ozone, carbon monoxide, and particulate matter are still high enough to present hazards to children. Although healthy children appear to experience losses in pulmonary function that are comparable to those observed in adults for a given dose of ozone, children do not report symptoms to the same extent, possibly because they do not recognize the significance of respiratory symptoms. Epidemiologic studies from various locations indicate a relationship between outdoor air pollution and adverse respiratory effects in children, and the most common pollutants implicated are respirable particulates and ozone. Air pollution correlates with increased prevalence of chronic cough, chest illness, bronchitis, hospital admissions for respiratory conditions, and decrements in lung function. The effects of exposures to multiple pollutants need further investigation. Clearly, existing epidemiologic and toxicologic data indicate that exposure to ambient air pollution is associated with respiratory toxicity. The Academy offers the following recommendations to pediatricians: 1.Pediatricians should become informed about air pollution problems in the community. 2.Pediatricians caring for children at special risk, such as those with asthma and cystic fibrosis, should be aware that current levels of air pollution may cause deterioration in these children's pulmonary function and may aggravate their symptoms. 3.Pediatricians who serve as physicians for schools and for students participating in team sports need to be aware of the health implications of pollution alerts in order to provide appropriate guidelines to schools and other public agencies about the health hazards of air pollution. 4.Pediatricians can make parents aware of the predictable daily variation in ozone, especially its tendency to peak in the afternoon. When ozone levels are elevated, it may be possible to decrease children's exposure by scheduling outdoor sports earlier in the day. 5.Pediatricians can help children by expressing their concern about the child health hazards of air pollution to their governmental representatives and to policy makers in state and federal government agencies.
Air Pollution and the Elderly (Benjamin)
Senior citizens have been identified as a population at special risk with regard to environmental pollution. Senior citizens have the advantage of a longer-range perspective than most citizens and have accumulated considerable wisdom. However, their age puts them at a disadvantage in terms of health because of environmental pollution hazards' cumulative nature. Aging individuals are more susceptible to air pollution because of the declining margin of safety in various organ systems, including the respiratory and immune systems, and because, in some cases, of the cumulative effect of environmental hazards. Seniors, along with children, are most at risk in severe air pollution episodes. Skin cancer and other malignancies are much more prevalent among the elderly, likely the cumulative effect of sun exposure over time expressing itself. The elderly are also affected by environmental pollution in other ways. For example, there is concern about their emotional health related to the environment, especially if they live in areas with serious air pollution problems, which may cause stress, anxiety, and depression in addition to physical problems. It is well known that many seniors, as they approach and live in retirement, become concerned about their economic situation and protecting and enhancing the value of their property. Many seniors cannot move from the homes in which they have lived for many years because of stringent economic circumstances. As the urban environment deteriorates with increased air pollution among other environmental problems, the value of their property does as well, and their stress and anxiety certainly increase. Those seniors who are more fortunate in terms of economic circumstance also face problems. For example, those who may have relocated to the "sun belt" retirement areas, especially those in Florida, Southern California, or Arizona, already see a deterioration in the quality of life and lifestyle there. Even these areas are experiencing increased traffic, air pollution, water pollution (and in some cases, severe lack of water as aquifers are being drained), as well as many other negative environmental effects. Not only is their personal life and health affected, but their social activities, especially those outdoors, are compromised as well. Thomas Benjamin, President, Environmental Alliance for Senior Involvement.
We are indebted to the National Association of Physicians for the Environment. Funding support came from the National Institute of Environmental Health Sciences with additional support from American Medical Association, American Academy of Otolaryngology-Head and Neck Surgery, Inc., American Academy of Dermatology, National Heart, Lung and Blood Institute, National Library of Medicine, Agency for Toxic Substances and Disease Registry