Air Pollution and Human Health

Air pollution can affect our health in many ways with both short-term and long-term effects.

Examples of short-term effects include irritation to the eyes, nose and throat, and upper respiratory infections such as bronchitis and pneumonia. Other symptoms can include headaches, nausea, and allergic reactions. Short-term air pollution can aggravate the medical conditions of individuals with asthma and emphysema. In the great "Smog Disaster" in London in 1952, four thousand people died in a few days due to the high concentrations of pollution.

Air pollution causes a variety of health problems for people of all ages; however, the elderly, young, sick, disabled and poor are more disproportionally affected. This is also the case when comparing poorer nations that have less pollution restrictions to wealthier and more environmentally regulated countries. Even small doses and short exposure times to pollutants can bring on an asthma attack or worsen a preexisting condition. Short term health effects of air pollution can exacerbate pulmonary issues that can lead to death.

Eye, Nose and Throat Irritation

1. Smog, particulate matter, ozone, nitrogen dioxide and sulfur dioxide can all contribute to ear, nose and/or throat irritation. Smog is a combination of smoke and fog. Smoke contains particulate matter which can severely irritate the eyes, nose and throat. Even short term exposure to significant particulate matter can cause intense coughing spells, sneezing, eye watering and burning. Similarly ozone can cause coughing, wheezing and a dry throat. Nitrogen dioxide irritates the lungs and throat while sulfur dioxide narrows the airways, causing wheezing, shortness of breath and tightening in the chest. High concentrations of sulfur dioxide in air pollution can cause burning in the nose.

Bronchitis and Pneumonia

2. Short term exposure to air pollution can cause or aggravate lower respiratory conditions such as bronchitis and pneumonia. Children are especially affected by polycyclic aromatic hydrocarbons, or PAHs, which can cause acute bronchitis. PAHs are released when fuel such as wood and coal are burned, as well as from grilling food and vehicle emissions. In addition, indoor air pollution from cooking fuels is detrimental to women and children across the world. According to the World Health Organization, exposure to indoor pollution more than doubles the risk of pneumonia.

Asthma and Emphysemia

3. People with chronic conditions like asthma and emphysema are especially vulnerable to short term exposure to air pollution. Nitrogen dioxide affects asthmatic people more intensely than others. It causes those with asthma to be more susceptible to lung infections and asthma triggers like exercise and pollen. Sulfur dioxide affects people with chronic conditions as well. Since it tightens the airways it can cause people with asthma or emphysema to have stronger symptoms than normal and an increased lack of breath. Air pollution from industrial plants, factories and automobiles all contribute significantly to an increase in asthma attacks.

Allergic Reactions

4. One of the short term effects of air pollution is an increase in the likelihood of allergic reactions. Not only do people with chronic conditions like asthma and emphysema need to pay attention to pollution indexes but now people with allergies are advised to do so as well. Pollution acts as a trigger to inflame already existing allergic reactions. Ozone is one of the main culprits. People who have strong allergies may want to stay clear of high traffic areas like freeways and highways; ozone is particularly acute in these areas.

Air Pollution and Mortality

5. Air pollution can lead to death in many cases. The World Health Organization estimates that indoor air pollution from solid fuel leads to approximately 1.6 million deaths per year. During London's "Smog Disaster" in 1952 about four thousand people died in just a few days because of a high concentration of air pollution. Carbon monoxide is also a quick and silent killer. It bonds to the blood's hemoglobin, slowly suffocating people as they breath. Carbon monoxide is especially dangerous indoors during the winter because it originates from unburnt fuel and settles close to the ground in cold seasons.

Sources of Air Pollution

6. The main source of air pollution is fuel. Burning fields, wood fires, vehicle emissions, cooking and heating oil all contribute to air pollution. Coal burning plants also release tons of particulates into the atmosphere. Industrial plants release toxins from smoke stacks and even household products containing formaldehyde can cause respiratory irritation.

Long-term health effects can include chronic respiratory disease, lung cancer, heart disease, and even damage to the brain, nerves, liver, or kidneys. Continual exposure to air pollution affects the lungs of growing children and may aggravate or complicate medical conditions in the elderly.

Exposure to air pollution contributes to the development of cardiovascular diseases (heart disease and stroke).

A person’s relative risk due to air pollution is small compared with the impact of established cardiovascular risk factors such as smoking, obesity, or high blood pressure. However, this is a serious public health problem because an enormous number of people are exposed over an entire lifetime.

Background

Until May of 2004, the American Heart Association had not issued any expert reviewed statement about the short-term and long-term effects of chronic exposure to different pollutants. This was due to flaws in research design and methodology of many pollution studies. During the last decade, however, epidemiological studies conducted worldwide have shown a consistent, increased risk for cardiovascular events, including heart and stroke deaths, in relation to short- and long-term exposure to present-day concentrations of pollution, especially particulate matter.

Elderly patients, people with underlying heart or lung disease, lower socioeconomic populations and diabetics may be at particularly increased risk. More research is needed to find out the differential toxicity of various constituents of air pollution.

Components of Air Pollution

Air pollution is composed of many environmental factors. They include carbon monoxide, nitrates, sulfur dioxide, ozone, lead, secondhand tobacco smoke and particulate matter. Particulate matter, also known as particle pollution, is composed of solid and liquid particles within the air. It can be generated from vehicle emissions, tire fragmentation and road dust, power generation and industrial combustion, smelting and other metal processing, construction and demolition activities, residential wood burning, windblown soil, pollens, molds, forest fires, volcanic emissions and sea spray. These particles vary considerably in size, composition and origin.

Particulate Matter and Sulfur Dioxide

The concentrations of both particulate matter and sulfur dioxide often change in parallel. The oxidation of sulfur dioxide in the atmosphere is linked with the formation of various particulate compounds, including acid sulfates.

A 1994 report on the adverse effects of particulate air pollution, published in the Annual Reviews of Public Health, noted a 1 percent increase in total mortality for each 10 mg/m³ increase in particulate matter. Respiratory mortality increased 3.4 percent and cardiovascular mortality increased 1.4 percent. More recent research suggests that one possible link between acute exposure to particulate matter and sudden death may be related to sudden increases in heart rate or changes in heart rate variability.

The Environmental Protection Agency (EPA) has declared that "tens of thousands of people die each year from breathing tiny particles in the environment." A recent report released by the nonprofit Health Effects Institute in Cambridge, Mass., agrees with the EPA assessment. This study was reviewed by Science magazine and clearly shows that death rates in the 90 largest U.S. cities rise by 0.5 percent with only a tiny increase – 10 micrograms (mcg) per cubic meter -- in particles less than 10 micrometers in diameter. This finding is similar to those of other studies throughout the world. The case is stronger with this study, because it eliminated several factors that could confound the interpretation of the data, such as temperature and other pollutants.

The number of deaths due to cardiac and respiratory problems may be small when looking at individual cities with small particles in the environment. The combined long-term effect of studies in several large cities predicts 60,000 deaths each year caused by particulate matter. This is a staggering loss of life that can be eliminated by stricter emissions standards as proposed by the EPA.

Secondhand Tobacco Smoke

Secondhand smoke, also known as environmental tobacco smoke, is the single largest contributor to indoor air pollution when a smoker is present. Studies of secondhand smoke indicate that air pollution in general can affect the heart and circulatory system. Previous research has established that exposure to the secondhand smoke of just one cigarette per day accelerates the progression of atherosclerosis – thus it is plausible that even low doses of air pollution could negatively affect coronary functions.

Carbon Monoxide

Carbon monoxide (CO) is a colorless, odorless and highly poisonous gas. It's a common air pollutant associated with combustion reactions in cars and other vehicles. It's also in cigarette smoke. When the level of CO in blood increases, the level of oxygen that blood can carry decreases. That's why CO in any level is harmful to your body -- and high levels may prove deadly. Long-term, low-level exposure to carbon monoxide may lead to serious respiratory diseases. Smoking tobacco and breathing environmental tobacco smoke raise CO levels in your blood, eventually leading to disease.

Carbon monoxide levels in the blood of nonsmokers vary depending on the quality of air that they generally breathe. The levels are usually 0-8 parts per million (abbreviated ppm). The CO level of smokers is much higher, but it depends on when and how much they smoke, and how they smoke (cigar, pipe, cigarette, etc.). A person who smokes one pack of cigarettes a day has a blood CO level of 20 ppm; someone who smokes two packs a day may have a blood CO level of 40 ppm. When smoking stops, the blood CO level should return to normal in a few days.

Nitrogen Dioxide

Nitrogen dioxide (NO2) is a precursor to ozone (O3) formation. Current efforts to reduce ozone levels also target reductions in NO2 levels. In contrast to ozone, NO2 is often found at higher levels indoors compared with outdoors. Mainly this occurs in settings where gas stoves and kerosene heaters are being used.

The main sources of NO and NO2 in outdoor air are emissions from vehicles and from power plants and other fossil fuel-burning industries. NO2 levels vary with traffic density. Annual average concentrations range from 0.015-0.035 ppm. Some highly congested areas like metropolitan Los Angeles ranged from 0.020-0.056 ppm in 1990. Estimates of concentrations inside vehicles in Los Angeles ranged from 0.028-0.078 ppm, where average commuting time was about 6.5 hours per week.

People with respiratory or heart problems should avoid prolonged exposure to high-traffic areas and unventilated heating elements in their homes.

People with asthma appear to be especially vulnerable to the effects of acute NO2 exposure. Healthy people, by contrast, don't seem to show detectable changes in lung function. Exposure to high levels (20 ppm) for several weeks or longer causes emphysema-like changes in the lungs of animals.

EPA Air Quality Standards

The U.S. Environmental Protection Agency (EPA) introduced its 1997 National Ambient Air Quality Standards (NAAQS) to educate the public about daily air quality levels, including information about ozone and particulate matter levels. This daily Air Quality Index was updated in 2003 to include information on fine particle pollution. This index provides information each day for more than 150 cities along with a health alert system that reflects recommended changes in activity on days when pollution is high. These daily updates can be found on the EPA Web site at www.epa.gov/airnow and in many newspapers across the country.

The American Heart Association supports these EPA guidelines for activity restriction for people with heart disease or those who have certain cardiovascular risk factors and for people with pulmonary disease and diabetes and the elderly.

Nineteen percent of all U.S. counties with air-quality monitoring systems are presently not meeting these standards. This inadequacy soars to much higher estimates in regions such as the industrial Midwest (41 percent) and California (60 percent).

Air Pollution Impact in U.S. Cities

Another study confirmed the importance of variations of pollution within a single city. Its findings suggested that a person’s exposure to toxic components of air pollution may vary as much within one city as across different cities. After studying 5,000 adults for eight years, the researchers also found that exposure to traffic-related air pollutants was more highly related to mortality than were city-wide background levels. For example, those who lived near a major road were more likely to die of a cardiovascular event.