Air Pollution: The Silent Pandemic Shortening Worldwide Life Expectancy
By Karen Oles, PharmD, MS
We are all pretty focused on the COVID-19 pandemic but there is another silent pandemic that should be on our radar: air pollution, and the detrimental effect it is having on human health, even on the mortality rate from COVID-19.
Exposure to air pollution is increasingly related to a host of diseases and an increased risk of mortality around the world. As described in the The State of Global Air 2019 report, air pollution is the fifth leading risk factor for mortality in the world, outranked only by dietary risk, hypertension, tobacco use, and elevated fasting blood glucose. Air pollution is a risk factor for more deaths than malnutrition, alcohol use, abnormal LDL, renal disease, or elevated body mass index. In 2017, 4.9 million deaths worldwide (or 8.7% of all deaths) were attributed to air pollution. Currently, exposure to air pollution is estimated to reduce the average worldwide human life expectancy by three whole years.
Air pollution also contributes to global warming through the production of greenhouse gases. In turn, the warming temperature increases the level of airborne pollen and, in some cases, pollutants, such as ozone. While the burning of fossil fuels drives global warming, climate change in turn enhances the risk and extent of wildfires, adding further particle and ozone pollution to the atmosphere.
The burden of disease falls disproportionately on the least developed nations. And for developed nations, pollution and its associated diseases fall most severely on the socially disadvantaged. The combination of pollutants and allergens are particularly problematic to those with underlying respiratory disease or allergies. Particulate matter may also serve as a vector for pathogens.
Air Pollution and COVID-19
Chronic exposure to air pollution causes lung and heart damage and can make people more susceptible to COVID-19 and other pathogens. To quantify the effect of air pollution on the current COVID-19 pandemic, a study in the US found that a small increase (1mcg/m3) in small particle pollution was associated with a 15% increase in mortality from COVID-19.
The COVID-19 pandemic has decimated economic activity and, as a consequence, slashed global pollution. Inadvertently, this has created the largest environmental experiment ever conducted.
In China, a country with some of the worst air quality in the world, it is estimated that the number of deaths from COVID-19 was actually less than the number of lives saved by the improvement in air quality.
A similar but smaller experiment occurred when a steel mill in Utah was shut down for 13 months. Rates of pneumonia, pleurisy, bronchitis, and asthma as well as total mortality decreased, indicating a substantial and immediate health benefit from the reduction of air pollution in the region.
Particles and Chemicals in Our Air
Small liquid or solid particles that are readily absorbed by the lung are divided into “fine particles” of less than or equal to 2.5 micrometers in diameter (otherwise known as PM2.5) and “coarse particles” of 2.5-10 micrometers (otherwise known as PM10). For comparison, the diameter of a human hair is 50-70mcg.
Fine particles pose the greater risk to our health. They are able to enter the bloodstream when inhaled. The higher surface to volume ratio of fine particles allows them to carry more pollutants into body.
Ultra fine particles are less than 0.1 micrometer in diameter: These particles can deposit deep in the lungs, in alveolar space. Less is known about these particles but they may be the most risky to human health.
There is no safe level of particle pollution.
Concentrations of particles are measured as micrograms per cubic meter of air (mcg/m3). The World Health Organization (WHO) guideline for annual average particle pollution for PM2.5 is set at 10mcg/m3, which the organization admits does not completely eliminate the deleterious effects of air pollution on human health.
Worldwide, 92% of people live in areas that exceed this upper limit of 10mcg/m3. In the U.S., the average annual average PM2.5 concentration is 8mcg/m3. The level of PM2.5 in the U.S. declined from 1990 to 2017, but has risen in recent years. In less developed countries, the concentration of PM2.5 is around four to five times higher than levels in the U.S.
Common substances found in particles include acids, organic compounds, metals, soil and allergens. The different substances found in particles are based on their size, as described below:
Particles between PM2.5 and PM10: Mold, pollen, and dust
Very small particles (PM2.5): Metals, combustion particles, and organic compounds
Ultra fine particles: Diesel combustion, other types of combustion and nanotechnology.
Particulate matter is created from transportation, industry, agriculture, construction, and wood burning. High sulfur diesel pollution is the main contributor to black carbon, a key component of PM2.5. Wildfires account for 15-20% of PM2.5 and prescribed burns and agricultural burns 15%.
The major chemicals causing air pollution include carbon monoxide, sulfur dioxide, nitrogen dioxide, and ground ozone, all of which are common lung irritants. Ground ozone (as opposed to stratosphere ozone which reduces UV radiation) is formed from photochemical reactions, primarily from volatile organic compounds (VOCs) and nitrogen oxides. Ground ozone (measured in parts per billion) has acute effects on lung function, resulting in more frequent and severe exacerbations of asthma. Ozone levels are often higher in the developed world due to industrialization .
Noise pollution, an important risk factor for cardiovascular disease, is often elevated in high traffic and industrial areas. Noise can act as a confounder for the effects of air pollution on health outcomes. Whether air and noise pollution have synergistic or additive effects is controversial. Noise pollution, like air pollution, is also a risk factor for diabetes, impaired cognition, and potentially other health concerns.
Indoor Air Pollution
The level of indoor pollutants can be as much as 10 times greater than outdoor pollutants due to poor home ventilation and the accumulation of air pollutants that originate in the home. Indoor air pollution is worst in homes that use solid fuels (such as coal, dung, wood, or biomass) to cook and heat their homes which more often occurs in underdeveloped countries. Children are most likely to be affected.
In the US, indoor PM2.5 levels are 50-70% of outdoor levels. It is estimated that, in the US, the general population spends 89% of their time indoors and, as a result, most exposure to outdoor air pollution occurs indoors. Because of all of this, awareness of indoor air pollution is critical.
Common indoor air pollutants include radon, asbestos, lead (in homes painted before 1978), nitrogen dioxide, smoke, carbon monoxide (primarily from combustible byproducts), house dust mites, and mold. Mold growth occurs when the indoor humidity is over 60% and is recognized to be a problem in about 10-50% of households. The risk of Legionnaires disease also is increased in moist environments.
Volatile organic compounds (VOCs) are carbon-containing compounds that primarily exist as vapor at room temperature. They are introduced into homes by degradation of building materials (worse in moist environments), microbial VOCs (from mold), new furnishings, cleaning chemicals, personal care products, poorly functioning appliances (such as stoves with inadequate ventilation), and from outdoor air pollution. VOCs generally take 2-8 weeks to decay. Formaldehyde, polycyclic organic matter (such as polycyclic aromatic hydrocarbons), naphthalene, benzene, trichloroethylene, and tetrachloroethylene are common chemicals found in homes.
VOC exposure is associated with sensory irritation (eye, nose, and throat irritation), headaches, fatigue, nausea, loss of coordination, cognitive decline, thyroid toxicity, liver and renal impairment, immune system impairment, cancer, and effects on the reproductive and endocrine systems. There is also evidence linking VOCs to the exacerbation of allergic, dermatological, and respiratory diseases, with the strongest evidence for formaldehyde.
Home indoor air quality monitors typically measure particle count, VOCs, and carbon dioxide. Indoor particle pollution can be removed by high efficiency particulate air (HEPA) filters. Some filters are even designed to remove >99% of particles as small as 0.003 microns. VOCs are not as readily removed as particles; to remove VOCs, activated carbon and other adsorbents may be added to the filtration system.
Effects on Health
The majority of air pollution related major disease is cardiovascular, followed by neoplasm and chronic respiratory disease. Cardiovascular diseases are the leading cause of premature death from air pollution and are responsible for roughly 43% of the total loss in life expectancy. Respiratory infections, including tuberculosis (TB), diabetes, chronic renal impairment, dementia, and venous thrombosis are also related to air pollution.
In 2017, worldwide exposure to elevated concentrations of PM 2.5 was ranked the 3rd leading risk factor for type 2 diabetes deaths and disability adjusted life years (DALYs). In one study, 14% of childhood asthma cases and 15% of all childhood asthma exacerbations were attributed to traffic pollution.
Older adults and the elderly carry most of the burden of air pollution. In 2017, 88% of deaths caused by PM2.5 occurred in people age 50 and older and 55% in people age 70 and older. Children, pregnant women, and immuno-compromised patients are also at higher risk.
As described in the 2019 State of Global Air Report, air pollution is responsible for 41% of global deaths from chronic obstructive pulmonary disease (COPD), 20% of deaths from type 2 diabetes, 19% of deaths from lung cancer, 16% of deaths from ischemic heart disease, and 11% of deaths from stroke. Air pollution also accounts for 35% of deaths from lower-respiratory infection.
A case-control study published in 2019, evaluated the association between the primary diagnosis at hospitalization and the concentration of PM2.5, based on Medicare data collected between 2000 and 2012, for patients age 65 and older. The short-term concentration of PM2.5 was determined by using national data based on zip codes for the day of and the day before hospitalization. Diseases which had the strongest correlation with PM2.5 (in order of strongest to weakest) were pneumonia, heart failure, septicemia, fluid and electrolyte disorders, urinary tract infections (UTIs), renal disease, COPD and bronchiectasis, acute myocardial infarction (MI), cardiac dysrhythmias, and type 2 diabetes with complications.
Another study of 635 counties in the U.S. found that a 5% increase in fine particles occurred between 2016 and 2018, accounting for an excess of 9,700 premature deaths in persons 30 years and older. 80% of the premature deaths were in the elderly and 43% of the premature deaths were in California. The authors suggest that wildfires, lack of enforcement of EPA clean air standards, and increased economic activity were responsible.
Think locally: The Air Quality Index and North Carolina Issues
The air quality index (AQI) is used to recommend limitations in outdoor activity, especially in susceptible persons. The highest level of outdoor pollution usually occurs from 2pm to 7pm. The AQI measures ground level ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The range of the reported AQI is from 0-500 with 301-500 being hazardous. An AQI of 100 corresponds to the national standard for pollution; AQIs below 100 are considered safe for most people. An AQI of 101-150 is “elevated for sensitive groups” (Code Orange). See the Air Quality Color Guide below for more information.
On a state level, there are several organizations that can provide helpful information on air quality, including:
Air Now - Shows real time air quality by zip code. You can subscribe to receive this information by text or email.
Clean Air Carolina - A North Carolina-based organization that provides educational materials and opportunities for citizen involvement in air monitoring (the Airkeepers Program) and advocacy.
Medical Advocates for Healthy Air (MAHA) - The health professional arm of Clean Air Carolina. MAHA provides training across North Carolina to inform health professionals about the relationship between air quality, climate change and health. MAHA develops specific scientifically-based position statements and letters in conjunction with other environmental organizations to effect change on local and national issues.
Conclusion
The interconnectedness of air pollution, climate change, and health are indisputable and these problems have been long undervalued in public policy. It is estimated that eliminating air pollution would save the US economy 4% of the GDP in averted healthcare costs. The impact of air pollution on both acute and chronic diseases is substantial. If you would like to increase your impact as a concerned citizen and health professional, consider signing up for newsletters from Clean Air Carolina and MAHA and add your voice to the endeavor to reduce air pollution.