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Air Toxics Program

New York State's air program protects the public and environment from the adverse effects of exposure to toxic air contaminants. In 1968, the State enacted 6 NYCRR Part 212, Process Operations (leaves DEC website) to determine how much control is needed to reduce air pollution. These emissions are from industrial processes and the burning of waste fuels. Additionally, the State enacted 6 NYCRR Part 257 (leaves DEC website) to set air quality standards for nine toxic air contaminants.

The State's air toxic program evolved over several decades. Our knowledge grew about how air pollution affects public health and the environment. This advanced knowledge included how to assess air concentrations of air pollution and technological advances in air pollution control. These advances have resulted in the implementation of stronger air pollution abatement strategies over the years to improve air quality and to better ensure the protection of public health and the environment.

On June 14, 2015, 6 NYCRR Part 212 was updated. To assist the public with understanding the changes, the Division of Air Resources released DAR‐1: Guidelines for the Evaluation and Control of Ambient Air Contaminants under 6NYCRR Part 212 (PDF). DAR-1 provides guidance to DEC permitting staff, the public, and the regulated community on the requirements of the air toxics program. DAR-1 outlines the control requirements for the emissions of air toxics based on an assigned Environmental Rating and provides guidance for implementing 6 NYCRR Part 212. All air guidance and policy documents are available as PDFs.

The air toxics program requires facility owners to perform an analysis to determine health impacts from inhalation exposures. This analysis requires the use of an air dispersion model. The model predicts the maximum 1-hour and annual air concentrations for each toxic air pollutant released. These concentrations are compared to Short-Term Guideline Concentrations (SGC) and Annual Guideline Concentrations (AGC) developed by DEC. This process and other factors are used to determine the degree of air pollution control. The guideline concentrations are updated every three years. More information can be found in DAR-1 (PDF).

AERSCREEN Modeling Software (Version 21112)

An essential component of deriving an Environmental Rating is determining the air concentration of the pollutant near the fence line. The AERSCREEN modeling software is able to perform this step. The modeled air concentration should be compared to the acceptable health-based concentration.

To assist in calculating the air concentration of a pollutant near the fence line, DEC is offering access to the USEPA's AERSCREEN model. The AERSCREEN model includes several component files which need to be incorporated into the AERSCREEN executable file to run properly. The AERSCREEN model can be downloaded as a zip file. DEC has included both the EPA's user guide and a condensed DEC user guide with suggestions on default options and programmatic contacts.

A new feature has been added to the AERSCREEN download; an Excel spreadsheet incorporating the AGC/SGC tables. The spreadsheet will allow the user to input data from multiple emission points and evaluate the offsite emissions by emission point and facility-wide.

Program Files Download and Set-up

On the C:\ drive, create a subfolder called C:\AERSCREEN.

  • Extract the compressed files to the C:\AERSCREEN directory. The program needs all the files within the compressed bundle to execute properly.
  • After unzipping the files to the C:\AERSCREEN directory, locate the DEC AERSCREEN User Guide.pdf for instructions to properly set up working directories and for running the model.


2021 DAR-1 AGC/SGC Tables

DEC established a listing of non-criteria air contaminants with acceptable ambient air concentrations to help the user of DAR-1 make an appropriate Environmental Rating determination. The acceptable air concentrations, in micrograms per dry standard cubic meter (µg/dscm), are listed for annual emission rates (AGC) and for hourly emission rates (SGC). A listing of AGC/SGCs were incorporated into the 1991 draft version of Air Guide-1 (DAR-1) under Appendix C and revised in 1995, 2000, 2003, 2007, 2010, 2014 and 2016. The 2021 AGC/SGC tables are located in Appendix A of DAR-1 (PDF).

Controlling Sources of Toxic Air Contaminants

The State has a long history of implementing programs to control toxic air contaminants. In 1957, the State Legislature created comprehensive air pollution control laws by passing the Air Pollution Control Act. The law recognized the need "to safeguard the air resources of the state from pollution.". The law focused on controlling air pollution from existing industry and preventing new releases of air pollution. The State's policy was and remains: "to maintain a reasonable degree of purity of the air resources of the state, which shall be consistent with public health and welfare and the public enjoyment thereof, the industrial development of the state...". By 1962, this law was the foundation for an air pollution control program to control emissions from industrial plants and from the combustion of fuels. Readers are encouraged to review EPA's Reducing Emissions of Hazardous Air Pollutants (leaves DEC website).

Addressing Mobile Source Pollution

Controlling air pollution from motor vehicles will improve air quality and protect public health. The 1965 Motor Vehicle Air Pollution Control Act prohibited the sale of high-emitting vehicles and the tampering of any pollution control devices. The 1970 Clean Air Act (CAA) required further emission reductions that focused on the criteria air pollutants. These included carbon monoxide, nitrogen oxides and hydrocarbons. EPA's national program and California's state program are leaders in the field. The CAA divides mobile sources into three categories:

  • on-road motor vehicles, such as cars, trucks, and buses;
  • airplanes; and
  • non-road vehicles and engines, including construction equipment, farm equipment, ships, locomotives, and tractors.

The 1990 Clean Air Act Amendments enabled EPA to develop further regulations that:

  • required the development of fuels that would burn cleaner.
  • targeted emissions of criteria air pollutants with new technology.
  • addressed toxic air contaminants.
  • authorized the promulgation of emission standards for non-road engines.
  • required onboard emission monitoring equipment.

The number of vehicles and vehicle miles traveled has increased, yet emissions have decreased. In 1995, the introduction of reformulated gasoline (RFG) resulted in significant decreases in ozone concentrations. Section 112(k) of the CAA deemed that RFG must be sold in certain ozone non-attainment areas. Federal rules limit the amount of benzene by volume in RFG gasoline which reduces tailpipe and evaporative emissions of benzene. RFG is required in the New York Metropolitan area (NYMA) and in Orange and Dutchess counties.

In 2007, EPA issued a more stringent rule to address releases of toxic air pollutants. The final standard lowered emissions of benzene and other toxic air pollutants by:

  • further lowering the benzene content in gasoline (lower than 1995 RFG levels).
  • reducing exhaust emission from passenger vehicles operated at cold temperatures.
  • reducing emissions that evaporate from portable fuel containers.

More history and federal programs can be found on EPA's Regulations for Emissions from Vehicles and Engines site (leaves DEC website).

Managing Mercury in Air

On February 16, 2012, EPA promulgated a National Emission Standard for Hazardous Air Pollutants (NESHAP) regulation to reduce toxic air pollutant emissions from coal-fired and oil-fired electric generating utilities. This action is also known as the Mercury and Air Toxics Standards (MATS) rule. The promulgated toxics rule reduces emissions of heavy metals, including mercury (Hg), arsenic, chromium, and nickel, and acid gases, including hydrogen chloride (HCl) and hydrogen fluoride (HF). These toxic air pollutants, also known as hazardous air pollutants (HAP) or air toxics, are known or suspected of causing cancer and other serious health effects.

In December 2018, EPA issued a proposal to reconsider the finding that it is "appropriate and necessary" to regulate HAP emissions from coal- and oil-fired electric utility steam generating units source category. EPA states the original analysis is flawed because it does not provide a full and fair accounting of the costs and benefits associated with implementation of the MATS rule. The State and other northeast states submitted comments to the docket disagreeing with EPA. DEC directly challenged EPA's cost/benefit analysis and listed examples of how the MATs rule has been successful.

Mercury Management in New York State

A picture showing how mercury enters the atmosphere and comes down as contaminated rain.
The Mercury Cycle.
(click on image to see a larger view)

Manmade (anthropogenic) emissions (past and present) have resulted in increased concentrations of mercury in the environment. According to the 2014 National Emission Inventory, approximately 52 tons of mercury are emitted from U.S. manmade sources every year. Over 43% of these emissions are from fossil fuel combustion sources and waste combustion. The global input to the atmosphere of all sources of mercury (including natural, oceanic and manmade) is calculated to be approximately 6,500 tons per year. Some of the mercury circulating through today's environment was released years ago. Land, water, and other surfaces can repeatedly re-emit mercury into the atmosphere after its initial release into the environment. Globally, artisanal and small-scale gold mining is the largest source of manmade mercury emissions (37%), followed by coal combustion (24%). Other large sources of emissions are non-ferrous metals production and cement production (United Nations Environment Program, Global Mercury Assessment, 2013).

The majority of mercury in the atmosphere is in the form of gaseous elemental mercury, Hg(0). This form of mercury can travel long distances in the atmosphere for many months. Some Hg(0) is converted into:

  1. a more water soluble form of mercury, divalent or oxidized mercury, Hg(II); and
  2. Hg(0), which can bind with particulate matter or aerosols to form particulate mercury, Hg(p)

These two forms of mercury are rapidly removed from the atmosphere in precipitation and fall onto land and into waterbodies, including the ocean.

In a waterbody and in the sediments of the waterbody, mercury may be converted by bacterial action into an organic form, methylmercury (CH3Hg). Acidic lake conditions are believed to promote this conversion. Methylmercury can bioaccumulate up the food chain as a result of ingesting contaminated aquatic organisms. Large fish and aquatic mammals at the top of the food chain may contain dangerously high levels of methylmercury. Contaminated fish become a human health hazard when they are consumed.

Methylmercury is slowly eliminated from the body. Animal studies and accidental poisonings have demonstrated that the embryo/fetus and young children are more sensitive to mercury than the adult. Methylmercury can travel across the placenta and accumulate in the fetal brain. It can also be found in breast milk. In the embryo/fetus and young children, methylmercury has been shown to inhibit the normal development of the nervous system and produce generalized lesions throughout the brain. Lower levels of exposure may not be apparent until later when the child's motor and verbal skills may be delayed or abnormal. Pregnant women may not show any effects, but their unborn children may be adversely affected. EPA has estimated that 8% of women of childbearing age in the general U.S. population have blood levels of mercury higher than EPA's reference level for mercury (leaves DEC website).

In adults, methylmercury concentrates in the kidneys, liver and brain. Nephritis, as well as neurological and cardiovascular effects, may result in adults. In conclusion, neurodevelopmental deficits are the most sensitive and well-documented health effects.

By reducing mercury emissions to the atmosphere from manmade combustion sources, we hope to reduce the level of mercury in fish flesh and decrease the subsequent threat to the health of humans and wildlife.


  1. 6 NYCRR Part 212, Process Operations (leaves DEC website). Promulgation of this regulation established a High Toxicity Air Contaminant list that addressed mercury emissions and established mercury limits to avoid bioaccumulation.
  2. 6 NYCRR Subpart 219-7, Mercury Emission Limitations for Large Municipal Waste Combustors Constructed on or before September 20, 1994 (leaves DEC website). Promulgation of Subpart 219-7 lowered the mercury emission limit for large municipal waste combustor plants from 80 µg/dscm or 85% removal, whichever is less stringent, to 28 µg/dscm or 85% removal, whichever is less stringent. This regulation will reduce mercury emissions and subsequent environmental loading of mercury in New York State and the northeast.
  3. 6NYCRR Part 246, Mercury Reduction Program for Coal-fired Electric Utility Steam Generating Units (leaves DEC website). Promulgation of this regulation reduced the allowable emissions from generating units and required continuous monitoring to ensure compliance.