Air Pollution Investigators: Which Agencies Take On This Role?

The Environmental Protection Agency (EPA) is a federal agency of the United States government that investigates air pollutants. The EPA was established by President Nixon in 1970 to protect human and environmental health and enforce laws such as the Clean Air Act. The Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for six common air pollutants, and the agency works with state, tribal, and local air agencies to achieve these standards. The EPA also investigates and pursues action against those who violate environmental laws, with criminal offenses comprising most of its investigations. The agency has various partners, including the National Association of Clean Air Agencies (NACAA), which is a non-profit association of air pollution control agencies in 40 states and other territories.

The Environmental Protection Agency (EPA)

One of the EPA's key responsibilities is enforcing the Clean Air Act, which requires the agency to set National Ambient Air Quality Standards (NAAQS) for six common criteria air pollutants. These pollutants include particulate matter, nitrogen oxides (NOx), and sulphur dioxide (SO2), which are known to have detrimental effects on human health and the environment. The EPA collaborates with state, tribal, and local air agencies to ensure compliance with these standards across the country.

The EPA also regulates emissions from various sources, including motor vehicles, ocean-going vessels, large ships, and stationary sources such as glass plants and cement manufacturing plants. For instance, the EPA enforces standards for marine diesel engines and the sulfur content of marine fuel under the Clean Air Act and the Act to Prevent Pollution from Ships (APPS). Similarly, the EPA's National Emission Standard for Hazardous Air Pollutants (NESHAP) aims to reduce toxic emissions from refineries, chemical plants, and other industries, as these emissions are linked to cancer, birth defects, and environmental degradation.

Additionally, the EPA has implemented the New Source Performance Standards (NSPS) for newly constructed or modified sources to control excess emissions of NOx, SO2, and particulate matter. These standards apply to a wide range of vehicles and engines, including cars, trucks, buses, recreational vehicles, generators, farm equipment, and marine engines. By enforcing these standards, the EPA strives to improve air quality and mitigate the health and environmental impacts of air pollution.

Clean Air Act (CAA)

The Clean Air Act (CAA) is a comprehensive federal law regulating all sources of air emissions, including stationary and mobile sources. The Act authorises the US Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) to protect public health, the environment, and the stratospheric ozone layer. The EPA is also responsible for regulating emissions of hazardous air pollutants, such as NOx, SO2, and particulate matter, which can cause respiratory illnesses, heart disease, and contribute to acid rain.

One of the goals of the CAA is to set and achieve NAAQS in every state, working in partnership with state, local, and tribal governments. The Act directs states to develop State Implementation Plans (SIPs), which include emission reduction strategies, to achieve these standards. The 1977 amendments to the CAA set more stringent requirements for areas not meeting the NAAQS and established the Prevention of Significant Deterioration (PSD) regulations for areas already meeting the standards.

The 1990 amendments to the CAA addressed four major environmental and health threats: acid rain, urban air pollution, toxic air emissions, and stratospheric ozone depletion. These amendments also established a national operating permits program and strengthened enforcement to ensure better compliance. Since the 1990 amendments, there has been an approximate 50% decline in emissions of key air pollutants, demonstrating the success of the CAA in improving air quality and protecting public health.

Section 112 of the CAA specifically addresses emissions of hazardous air pollutants. It requires the EPA to establish technology-based standards for "major sources" and certain "area sources". Major sources are defined as stationary sources emitting or having the potential to emit 10 tons or more of a hazardous air pollutant per year. The emission standards for major sources, known as Maximum Achievable Control Technology (MACT) standards, require the maximum degree of reduction in emissions.

The CAA also regulates marine engines and their fuels, including US-flagged marine diesel engines and ocean-going vessels. The EPA enforces CAA standards for these engines and implements international standards under the authority of the Act to Prevent Pollution from Ships (APPS). Overall, the Clean Air Act provides a comprehensive framework for improving air quality, reducing pollution, and protecting public health through the collaboration of federal, state, and local agencies.

National Ambient Air Quality Standards (NAAQS)

The Clean Air Act requires the US Environmental Protection Agency (US EPA) to set National Ambient Air Quality Standards (NAAQS) for six principal pollutants, often referred to as "criteria pollutants". These pollutants are common in outdoor air and are considered harmful to public health and the environment. The six criteria air pollutants are: particulate matter, ozone, nitrogen oxides, sulfur oxides, carbon monoxide, and lead.

The Clean Air Act identifies two types of NAAQS: primary standards and secondary standards. Primary standards are designed to protect public health, including that of sensitive populations such as asthmatics, children, and the elderly. They aim to ensure an adequate margin of safety for individuals and communities. On the other hand, secondary standards focus on public welfare protection. These standards safeguard against damage to soils, water, crops, vegetation, man-made materials, animals, wildlife, visibility, climate, and property. Secondary standards also address transportation hazards, economic values, and personal comfort and well-being.

The process of establishing NAAQS involves a comprehensive review of scientific literature, which is summarised in the Integrated Science Assessment (ISA). Based on the ISA, the US EPA conducts a risk and exposure assessment, documented in the Risk and Exposure Assessment (REA). The third document, the Policy Assessment (PA), integrates the ISA and REA findings into a policy context, exploring various alternatives and supporting the retention or revision of existing NAAQS. All three documents are released for public comment and peer review by the Clean Air Scientific Advisory Committee (CASAC), a subcommittee of the US EPA's Science Advisory Board. CASAC members are appointed by the US EPA Administrator for their expertise in relevant subject areas.

Once the documents are finalised, they are submitted to the US EPA Administrator, who selects a proposed NAAQS published in the Federal Register for public comment. After considering the comments, the Administrator may make changes to the proposed NAAQS and publishes the final version in the Federal Register. Federal law requires all states to attain the NAAQS, with non-attainment areas facing potential penalties, including withholding federal highway funds. The Clean Air Act mandates that the US EPA review and revise the NAAQS every five years to align with the latest scientific advancements.

National Emission Standard for Hazardous Air Pollutants (NESHAP)

The Environmental Protection Agency (EPA) is the agency responsible for investigating and enforcing air pollution standards in the United States. The EPA works with state, tribal, and local air agencies to enforce the Clean Air Act and achieve National Ambient Air Quality Standards (NAAQS) for six common air pollutants, known as criteria air pollutants.

One of the key standards enforced by the EPA is the National Emission Standard for Hazardous Air Pollutants (NESHAP). NESHAP is a stationary source standard that applies to the emissions of hazardous air pollutants (HAPs) from corporations, institutions, and agencies at all levels of government within the United States. HAPs are those pollutants known or suspected to cause cancer, serious health issues (such as respiratory issues leading to illness), reproductive issues, birth defects, or adverse environmental effects. Leaks, flares, and excess emissions from refineries, chemical plants, and other industries can contain HAPs. Leaking equipment is the largest source of HAP emissions from petroleum refineries and chemical manufacturing facilities.

To ensure compliance with NESHAP, the EPA conducts inspections of regulated facilities. These inspections include examining processes with emissions points, wastewater discharges, and adherence to design and work practice standards. Sources may also be required to install and operate continuous emission monitors. NESHAP sources that meet the Clean Air Act definition of "major source" are subject to a full compliance evaluation by the state or regional office at least once every two years.

The EPA's National Enforcement and Compliance Initiatives focus on significant environmental risks and non-compliance patterns. For Fiscal Years 2014 to 2016, the strategy concentrated on categories of sources emitting HAPs. The EPA proposed amendments to NESHAP in 2024, including removing exemptions for hazardous waste combustors during periods of malfunction and adding electronic reporting provisions to enhance compliance monitoring and enforcement.

State Implementation Plans (SIPs)

In the United States, the Environmental Protection Agency (EPA) is the federal agency responsible for enforcing the Clean Air Act and investigating air pollutants. The EPA works in conjunction with state, tribal, and local air agencies to achieve and maintain National Ambient Air Quality Standards (NAAQS) for six common air pollutants, known as criteria air pollutants. These pollutants include NOx, SO2, and particulate matter, which are emitted by sources such as large glass plants, cement manufacturing plants, and motor vehicles.

The Lowest Achievable Emissions Rate (LAER) is a critical metric employed by the EPA to evaluate the acceptability of emissions from new or modified major stationary sources under SIP guidelines. LAER standards are mandated for stationary sources located in regions with less-than-ideal air quality, also known as non-attainment air-quality regions. This stringent standard surpasses the requirements of the best available control technology and reasonably available control technology standards.

The SIPs are dynamic and adaptable, as demonstrated by the 1977 amendments to the Clean Air Act. Initially, a rule in the Act mandated a reduction in sulfur dioxide (SO2) emissions from coal-fired power plants in Ohio between 1970 and 1977. The SIP at the time aimed to increase the height of smokestacks in these plants, dispersing the SO2 over a wider area and reducing measured levels near the source. However, recognizing the limitations of this approach, Congress restricted the use of tall smokestacks in the 1977 amendments, encouraging more direct methods of emission reduction.

Overall, SIPs play a vital role in ensuring that states take ownership of their air quality and work collaboratively with the EPA to achieve and sustain clean air for their citizens. These plans are a testament to the collaborative nature of environmental governance in the United States, where federal and state agencies work together to protect public health and the environment.

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