Hazardous Air Pollutants: Understanding Their Unique Characteristics

Hazardous air pollutants (HAPs) are those that are known or suspected to cause cancer or other serious health effects, such as reproductive issues, birth defects, or adverse environmental effects. HAPs are regulated by the US Environmental Protection Agency (EPA) through the National Emission Standards for Hazardous Air Pollutants (NESHAPs) and Maximum Achievable Control Technology standards (MACTs). These standards aim to control and reduce HAP emissions from specific source categories, which can include both stationary sources (industrial processes) and mobile sources (vehicles). The list of HAPs is periodically reviewed and revised to include pollutants that present a threat to human health or the environment, and as of 2022, there are 188 federally regulated HAPs.

Hazardous air pollutants (HAPs) are known to cause cancer, birth defects, and other serious health issues

Hazardous air pollutants (HAPs) are toxic substances known to cause cancer, birth defects, and other serious health issues. They can take the form of gases, compounds, or metals and are released into the atmosphere through a variety of sources, including industrial emissions, coal-fired power plants, vehicle emissions, and accidents during the transportation of hazardous materials.

The adverse health effects of HAPs are well-documented. Exposure to HAPs has been linked to an increased risk of cancer, particularly lung cancer. Research has shown that exposure to particle pollution can cause changes in airway cells, triggering the development of lung cancer even in individuals who have never smoked. The World Health Organization (WHO) estimates that nearly half of lung cancer cases in non-smokers are attributable to air pollution. Furthermore, HAPs have been associated with birth defects and other serious health issues, including respiratory and cardiovascular diseases.

The Clean Air Act, enacted in 1990, originally identified 189 HAPs for regulation, which has since been modified through rulemaking. As of 2022, there are 188 federally regulated HAPs in the United States. These pollutants are regulated by specified controls, such as Maximum Achievable Control Technology standards (MACTs) and Generally Achievable Control Technology standards (GACTs). North Carolina, for example, has implemented a health-based toxic air pollutant control program that regulates 92 Toxic Air Pollutants (TAPs), with additional facility emission limits to ensure compliance with health-based acceptable ambient levels (AALs).

The Environmental Protection Agency (EPA) plays a crucial role in understanding, regulating, and monitoring HAPs. The EPA develops regulatory programs and conducts inspections of industrial facilities to ensure compliance with emission standards. The National Emission Standards for Hazardous Air Pollutants (NESHAPs) are stationary source standards that aim to mitigate the release of HAPs from industrial processes. By implementing these standards and regulations, the EPA strives to protect public health and mitigate the environmental impacts of HAPs.

HAPs are regulated by National Emission Standards (NESHAPs) and Maximum Achievable Control Technology standards (MACTs)

Hazardous air pollutants (HAPs) are those pollutants known or suspected to cause cancer or other serious health effects, such as reproductive issues, birth defects, or adverse environmental effects. HAPs are regulated by National Emission Standards (NESHAPs) and Maximum Achievable Control Technology standards (MACTs). NESHAPs are stationary source standards for hazardous air pollutants, meaning they apply regardless of whether a facility needs an air permit. There are two types of facilities covered by NESHAPs: major sources and area sources. Major sources have the potential to emit more than 10 tons per year of a single HAP or 25 tons per year of any combination of HAPs. Area sources, on the other hand, have the potential to emit less than the major source threshold and are typically small businesses.

MACTs are the standards used by the EPA to control and reduce HAP emissions from specific source categories. They offer several emission control options, each with extensive testing, monitoring, record-keeping, and reporting requirements. MACT standards generally apply to major sources of federally regulated HAPs. However, some area sources may use Generally Available Control Technologies (GACTs) instead of MACTs. GACTs are achievable control technology standards that apply to industrial and area source categories, such as paper mills and fuel combustion sources.

To ensure compliance with NESHAPs and MACTs, the EPA conducts inspections of facilities subject to the regulations. Existing sources typically have three years to comply with new standards, while new sources must comply at startup. Facilities covered by NESHAPs must submit initial notifications to the regulating agency, indicating their status and providing compliance updates. Additionally, the EPA's "Once-In-Always-In" policy, issued in 1995, stated that once a source was subject to a major source NESHAP, it would always be subject to the standard, regardless of its emissions. However, this policy was withdrawn in January 2018, allowing qualifying major sources to be reclassified as area sources.

It is important to note that not all HAPs are regulated by NESHAPs and MACTs. The Clean Air Act amendments of 1990 originally identified 189 HAPs for regulation, and this list has been modified over time. As of 2022, there are 188 federally regulated HAPs. Some states, like North Carolina, have their own health-based toxic air pollutant control programs that regulate additional TAPs (Toxic Air Pollutants) beyond those classified as HAPs.

The Clean Air Act amendments of 1990 originally identified 189 HAPs, this list is modified through rulemaking

The Clean Air Act Amendments of 1990 identified 189 HAPs (Hazardous Air Pollutants) for regulation. HAPs are pollutants that are "known to cause or may reasonably be anticipated to cause adverse effects on human health or adverse environmental effects". These pollutants are known or suspected to cause cancer, reproductive issues, birth defects, and other serious health issues. They are emitted from stationary sources (industrial processes) and mobile sources (cars, trucks, and other vehicles).

Prior to 1990, the Clean Air Act established a risk-based program, but few standards were developed. The 1990 amendments were significant as they revised Section 112 to require the issuance of technology-based standards for major sources and certain area sources. This marked a shift towards more proactive regulation and a focus on achieving tangible goals.

Since its inception, the list of HAPs has been modified through rulemaking. As of 2022, there are 188 federally regulated HAPs. Two pollutants have been delisted: caprolactam in 1996 and methyl ethyl ketone in 2005. On January 5, 2022, 1-bromopropane was added to the list. These changes reflect the evolving understanding of the hazards posed by these substances and the ongoing efforts to protect public health and the environment.

It is important to note that not all hazardous air pollutants are regulated in the same way. The EPA develops national enforcement initiatives that focus on significant environmental risks and non-compliance patterns. Additionally, states like North Carolina have implemented their own health-based toxic air pollutant control programs that regulate TAPs (Toxic Air Pollutants). Of the 92 TAPs regulated by North Carolina, 14 are not classified as HAPs, while 78 pollutants are common to both lists.

HAPs are emitted from stationary sources (industrial processes) and mobile sources (cars, trucks, etc.)

Hazardous air pollutants (HAPs) are substances that are known or suspected to cause cancer and other serious health and environmental effects. HAPs are emitted from both stationary sources (industrial processes) and mobile sources (cars, trucks, etc.).

Stationary sources of HAPs include major sources of emissions such as power plants, steel mills, and factories, as well as smaller emission sources like gas stations, dry cleaners, and consumer and commercial products like household cleaners and lawnmowers. These sources are regulated by the US EPA, which develops national enforcement initiatives and conducts inspections of facilities to determine compliance with regulations. The EPA also provides area and mobile source emissions estimates on its National Emissions Inventory (NEI) website.

To control HAP emissions from stationary sources, the EPA has established standards of maximum achievable control technology (MACT). These standards are performance-based, allowing facilities to use any technology to meet the required emission rate. However, the manner in which MACT standards are promulgated provides an incentive for companies to opt for the sanctioned technology. The EPA also promotes the development of pollution prevention technologies that are more cost-effective than predetermined control technologies.

Mobile sources of HAPs include on-road and off-road gasoline and diesel engines, aircraft, commercial marine vessels, and railroad emissions. These sources are also regulated by the EPA, which works to reduce emissions from both mobile and stationary sources through regulatory programs and compliance monitoring.

Overall, the regulation of HAPs aims to reduce their environmental and health impacts, which include adverse effects on human health, such as cancer, reproductive issues, and birth defects.

North Carolina has a health-based toxic air pollutant control program that regulates 92 Toxic Air Pollutants (TAPs)

Hazardous air pollutants (HAPs) are those that are known or suspected to cause cancer, birth defects, or other serious health and environmental effects. The US EPA included 189 HAPs in Title III of the 1990 CAAA (Clean Air Act Amendments). Since then, the list has been modified through rulemaking, with caprolactam and methyl ethyl ketone being delisted, and 1-bromopropane added. There are currently 188 federally regulated HAPs. HAPs are emitted from stationary sources (industrial processes) and mobile sources (cars, trucks, and other vehicles).

To ensure that AALs are not exceeded, North Carolina may require additional facility emission limits beyond those specified by applicable federal Maximum Achievable Control Technology standards (MACTs). Fourteen of the 92 North Carolina TAPs are not classified as HAPs, while 78 pollutants are common to both lists.

In 1985, a three-part study was initiated to define the nature and extent of toxic pollutant emissions, their sources, and to develop air toxic control regulations for North Carolina. This study revealed a significant toxic air pollution problem in the state, with emissions coming from several thousand point sources. As a result, a list of 80 chemicals, called TAPs, was compiled, and Acceptable Ambient Levels were set for each one by an expert panel from the North Carolina Academy of Sciences.

The DAQ operates a statewide air quality monitoring network to measure the level of pollutants in the outdoor air, develops and implements plans to meet future air quality initiatives, issues permits, ensures compliance with air quality rules, and educates the public on air quality issues. North Carolina is also investing $92 million in projects to reduce pollution, including electric vehicles and infrastructure.

Frequently asked questions