Julia Vanella is a staff writer for Brief Policy Perspectives and a first-year MPP student.

Air pollution “is a mix of hazardous substances from both human-made and natural sources,” composed of a mixture of gases, liquids, and particulate matter (PM). Particulate matter is a product of chemically and physically different materials that make up various particles, such as liquid droplets, solids, or semi-volatile materials found in the atmosphere. Although both human and biogenic sources release PM into the air, human activity makes up the majority of the main particulate matter present. The dominant kinds of human-made air pollution include vehicle emissions, fuel oils, natural gas to heat homes, coal-fueled power plants, as well as fumes from chemical production. Both human and biogenic air pollution releases particulate matter that can be harmful to one’s health. 

Larger particles, known as PM₁₀, released from dust, pollen, and mold, irritate one’s eyes, nose, and throat. Smaller particles, referred to as PM_2.5, however, are more dangerous because they can permeate the skin and enter one’s bloodstream more easily. According to the World Health Organization (WHO),  air pollution contributed to 4.2 million deaths in 2016. In 2019, WHO reported 99 percent of the world’s population resides in areas where pollution exposure is greater than the limits set by the organization. 

The WHO has recently toughened its air quality guidelines for the first time since 2005, as Southeast Asia has become the worst-impacted region by air pollution. The organization refers to air pollution as one of the largest environmental threats to human health, leading to seven million premature deaths yearly. The United Nations also has air pollution on its radar, as the organization characterized the threat as “on par with other major global health risks such as unhealthy diet and tobacco smoking.” 

In the Global Air Quality Guidelines (AQCs), the WHO adjusted almost all of their air quality guideline levels downwards, claiming that surpassing the new levels can lead to serious health risks, but following them can save millions of lives. While these WHO guidelines are not legally binding, the research conducted to determine their results are useful tools for policymakers to reduce air pollution emission levels and protect the public’s health, particularly the health outcomes.

Health Effects from Air Pollution

In the 1960s, research was conducted to determine the adverse effects of air pollution on adults. In 1973, epidemiologist Beate Ritz studied the effects of air pollution on birth outcomes in the Los Angeles area. Her studies suggested that mothers exposed to high levels of pollutants during pregnancy had babies with lower birth weights and that they were more likely to be born preterm compared to babies born to mothers who inhaled cleaner air. 

Although researchers have not yet identified all the potentially harmful effects of air pollution, research suggests that maternal exposure to air pollution between the levels of PM₁₀ and PM_2.5 during pregnancy could increase the risk of infant mortality, preterm birth, low birth weight, congenital malformations, and other adverse health effects. Immature fetuses are particularly vulnerable to toxicant exposure. Even inhaling PM_2.5 at relatively low levels may alter the size of a fetus’ developing brain, which may lead to future cognitive and emotional problems in adolescence.

While birth weight is most commonly used as an indicator of fetal growth, air pollution has also been shown to negatively affect fetal organs such as lungs. Possible windows for exposure occur during both prenatal and postnatal periods,  as the growth and development of the respiratory system occur during fetal life and continue through adolescence. Throughout this development, exposure may result in changes that comprise the respiratory health of the individual during childhood and adolescence. A study conducted in 2018 suggested that seven-year-olds, particularly boys, who were exposed to nitrates from vehicle emissions during weeks six through 12 of gestation had lower scores for lung capacity compared to kids exposed at lower levels. 

Looking Towards the Future

The United States Environmental Protection Agency (EPA) has made significant contributions to regulating air quality standards. Under the EPA’s Clean Air Act (CAA), the agency must set National Ambient Air Quality Standards (NAAQS) for six common air pollutants including carbon monoxide, lead, ground-level ozone, particulate matter, nitrogen dioxide, and sulfur dioxide. The CAA gives the EPA authority to set limits on how many particles can be released in the air anywhere in the United States from chemical plants, utilities, and steel mills. Under this act, states are required to establish a general proposal on how to meet the NAAQS standard in all areas of the country and a specific plan for each area that currently does not meet the standards set by the agency. 

While EPA’s policy was influential in regulating pollution emissions, more work needs to be done to address the releases of particulate matter that continue to negatively impact the public’s health. While there is no major legislation currently being considered that directly targets improving air quality, the Build Back Better Act includes funding to implement the largest effort to tackle the climate crisis in American history. The Act plans to significantly cut greenhouse gas pollution by 2030 and improve air quality for all. However, the bill has yet to pass, leaving room for the general public and climate activists wondering if this progressive act will ever become law. As the threat of climate change becomes more permanent, policymakers will hopefully bring air pollution and its correlation to fetuses’ health to the forefront of the policy agenda, and pass stricter legislation that will protect mothers and fetuses.