sun bathing | Josh Ellenbogen
Regulatory Differences in the Clean Air Act and the Clean Water Act
by Emma Dickinson
The Environmental Protection Agency (EPA) is an agency of the United States government. The EPA enforces laws which control environmentally harmful activities in order to protect both human and environmental health. The Clean Air Act (CAA) and the Clean Water Act (CWA) are both federal laws enforced by the EPA that aim to limit the degradation of natural resources, but with different approaches to pollution regulation. The CAA limits pollutant levels in ambient air to focus on the protection of human health, and the CWA limits effluent discharge based on technology. Understanding the regulatory differences between the CAA and the CWA helps us to acknowledge the challenges of environmental law and recognize why some measures or methods of regulation are insufficient.
Regulatory approaches are strongly affected by resource boundaries. Global death rates from unsafe water sources are considerably lower than they are for air pollution because water can easily be filtered and boiled prior to consumption (IHME, 2025). Water tends to stay within naturally defined boundaries like lakes and streams, so people can choose to obtain their drinking water from a different source. For example, horribly polluted waters of Ethiopia’s Akaki River do not have direct health effects on those living in Egypt. However, people cannot choose the source of air they breathe, and the smoke from the 2023 Canadian Wildfires had direct and significant impacts on residents in NYC (Chen et al., 2023). Ambient air is the general outdoor air that all people are exposed to regardless of intent, and since water boundaries are more defined, there is no such thing as ambient water. For this reason, only the CAA is able to regulate pollution levels in ambient surroundings.
While the CWA could regulate pollution levels in each stream, this measure would still be ineffective because of changing water volumes. There is extensive scientific research regarding the ways specific air pollutants affect human health, and there are known concentrations at which adverse effects can occur (Curtis et al., 2006). Since everyone has the potential to encounter health risks due to poor air quality, it is in the interests of both citizens and politicians alike to prevent ambient air from reaching those thresholds. Despite knowing what concentrations of pollutants cause impacts to human health, water volumes are constantly changing. Concentration is the mass of a solute in a given volume. Therefore, seasonal flow patterns result in constantly changing pollutant concentration levels. A factory cannot be responsible for water pollutant concentrations exceeding a set threshold if a major drought halves the stream discharge. Natural variation in flow rates and volume means that health-based water quality standards do not translate well into exact numbers for effluent reduction at a factory (Salzman & Thompson, 2024). Instead, the CWA requires facilities to treat water prior to discharge, matching the effectiveness of a certain type of technology (called BPTs: best practicable control technology currently available). While the facility does not need to use that specific technology, the water must be treated to the same degree the technology would provide. Setting effluent limits based on a technological standard prevents flow rate variations from fabricating compliance or violation and gives the facility freedom in how it chooses to meet the standard.
While the different approaches to pollution regulation are necessary, both methods have shortcomings. For example, regulating water pollution based on technological standards means that the CWA only effectively regulates point-source pollution (Salzman & Thompson, 2024). Point source pollution are pinpoint spots where pollution occurs (like pipes, leaks, and drains) and are extremely easy to identify. Nonpoint source pollution has no specific, discernible origin and includes agricultural runoff, pesticide drift, storm water overflow, and road salt runoff. Considering the majority of water pollution comes from nonpoint sources, technology-based regulation in the CWA is overall inefficient in tackling water quality concerns. Regulation based on direct human health impacts is not a perfect approach either. Methane in the atmosphere has immense ecological implications but does not greatly affect human health (Salzman & Thompson, 2024). Therefore, it is not included in the CAA’s 6 criteria pollutants (EPA, 2017).
Despite their shortcomings, the CAA and the CWA take necessary steps toward a healthy environment, setting rules to achieve basic air and water quality in the United States. While the primary goal of these laws is to protect human health, they also protect plants and animals. The CAA sets limits for 6 criteria air pollutants: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide. Sulfur dioxide chemically burns plants, ground-level ozone causes lung irritation in animals, and particulate matter alters stream acidity and nutrient availability (EPA, 2026; EPA, 2025a; EPA, 2025b). The CWA has a list of over 100 toxic and priority pollutants and includes contaminants like lead, nickel, and mercury. Animals that ingest heavy metals through their drinking water may suffer from altered developmental growth and have shortened lifespans (Rahman & Singh, 2019).
While the laws have different regulatory approaches and have definite shortcomings, the CAA and the CWA are the two most prominent federal laws in place to protect our basic resources (Library of Congress, n.d.). Environmental law must address the nuances of the resource itself, and this is ultimately why regulatory approaches cannot all be the same. When we understand this, we can recognize the legal difficulty in addressing other aspects of our environment (waste disposal, invasive species, endangered species, and habitat loss) and actively participate in finding new solutions to an earth in crisis.
References
Chen, K., Ma, Y., Bell, M. L., & Yang, W. (2023). Canadian wildfire smoke and asthma syndrome emergency department visits in New York City. JAMA, 330(14), 1385–1387. https://doi.org/10.1001/jama.2023.18768
Curtis, L., Rea, W., Smith-Willis, P., Fenyves, E., & Pan, Y. (2006). Adverse health effects of outdoor air pollutants. Environment International, 32(6), 815–830. https://doi.org/10.1016/j.envint.2006.03.012 IHME, Global Burden of Disease (2025). Data processed by Our World in Data. Number of deaths by risk factor [Data set]. https://ourworldindata.org/grapher/number-of-deaths-by-risk-factor
Library of Congress. (n.d.). Environmental Law: A Beginner’s Guide. Springshare.
IHME, Global Burden of Disease (2025). Data processed by Our World in Data. Number of deaths by risk factor [Data set]. https://ourworldindata.org/grapher/number-of-deaths-by-risk-factor
Emma Dickinson is a senior, majoring in Earth and Environmental Sciences with a minor in Ecology and Environmental Studies from Hershey, Pennsylvania. Emma plays the cello, loves to garden, and enjoys woodworking. Emma’s senior research focuses on black-legged ticks and aims to provide valuable information regarding public safety and protection from tick-borne diseases.