National Air Toxics Assessment & Ethylene Oxide

The U.S. Environmental Protection Agency (EPA) began the latest study of air toxic emissions across the United States in 2014. That data was compiled and released by the EPA in 2018 in a report called the National Air Toxics Assessment (NATA). The NATA is used as a screening tool to help identify areas of the country that require additional studies to better understand potential public health risks due to air toxic emissions.  

The 2014 NATA indicates potentially greater cancer risks in several areas of the country that are impacted by emissions from a specific air toxic called ethylene oxide (EtO). EtO is a flammable, colorless gas used to manufacture a range of products, including antifreeze, textiles, plastics, detergents and adhesives. It also can be used to sterilize medical and dental equipment. 

There is very little air monitoring data about EtO, locally or nationally. However, the EPA updated the toxicity value of EtO in 2016 based on calculations that showed long-term exposure risks to EtO are greater than previously thought. 

DHEC is committed to staying engaged nationally as the EPA works to establish standards for reducing hazardous air pollutant emissions like EtO. DHEC will also continue to work with South Carolina facilities and communities to reduce the potential health risks associated with air toxic emissions. 


What is the National Air Toxics Assessment (NATA)?

The NATA is EPA's ongoing review of air toxics in the United States. It serves as a screening tool for state, local and tribal air agencies to help identify which pollutants, emission sources, and/or localized areas should be studied further to better understand possible public health risks. 

The NATA calculates air toxics concentrations and long-term health risks into identified areas called “census tracts.” The 2014 report includes 106 census tracts in the United States with an estimated cancer risk greater than 100 in 1 million, which means there’s a likelihood that 100 in 1 million people (or 1 in 10,000 people) would develop cancer if they breathed air containing the same amount of the same air toxic every day for 70 years. The primary risk in many of these census tracts is driven by emissions of EtO. 

In South Carolina, NATA identified two census tracts with a total cancer risk greater than 100 in 1 million, both in the North Charleston area.  

What is EtO?

Ethylene oxide is a flammable, colorless gas used to make a range of products, including antifreeze, textiles, plastics, detergents and adhesives. EtO also is used to sterilize equipment and plastic devices that can not be sterilized by steam, such as medical and dental equipment. Some spices and dehydrated vegetables also are sterilized with EtO.

According to the Centers for Disease Control and Prevention (CDC), environmental exposures to EtO may also include vehicle exhaust and tobacco smoke. 

The Clean Air Act lists EtO as one of 187 hazardous air pollutants (HAP), commonly referred to as air toxics. 

What are the health risks of EtO?

According to the EPA, short-term inhalation exposure to high concentrations of EtO can cause headache, dizziness, nausea, fatigue, respiratory irritation and, in some cases, vomiting and other types of gastrointestinal distress. 

The EPA states that long-term exposure to EtO can irritate the eyes, skin, throat, and lungs, and can harm the brain and nervous system, causing headaches, memory loss, and numbness. Studies show breathing air containing elevated levels of EtO over many years can increase the risk of some types of cancers. Workers exposed to EtO are associated with an increased risk of cancers of the white blood cells, as well as an increased risk of breast cancer in females. 

It is important to recognize that each type of cancer has its own risk factors, some of which are better understood than others. It is very rare that a specific cause can be found for any particular case of cancer. According the Center for Disease Control’s Agency for Toxic Substances and Disease Registry (ATSDR), exposure to EtO is unlikely to result in non-cancer health effects. DHEC has evaluated the cancer data from the SC Cancer Registry and has not found any clusters of cancers associated with exposure to ethylene oxide.   

What is the U.S. EPA doing to reduce EtO nationally?

The EPA regularly reviews Clean Air Act regulations for facilities that emit hazardous air pollutants, including EtO, to ensure that they protect the public from significant risk. In November 2019, the EPA announced proposed amendments to the 2003  Miscellaneous Organic Chemical Manufacturing National Emission Standards for Hazardous Air Pollutants (NESHAP) rule (often referred to as the “MON”), which will reduce hazardous air pollutants, including EtO emissions, nationwide.  For more information about the EPA’s proposed rule, please visit EPA’s MON Risk and Technology Review webpage and MON Fact Sheet (PDF).  

The EPA has also begun review of the air toxics emissions standards for Commercial Sterilizers that use EtO. A proposal is expected in the coming months.

Based on EtO sampling the EPA has conducted in nine other states over the last six months, the EPA has found: 

  • There is no immediate short-term risk from levels of EtO found in the monitoring data.
  • There is a need to better understand how low levels of EtO vary seasonally and regionally over a longer-term period; and 
  • The amount of available data is insufficient to evaluate against long-tem health benchmarks.

For the latest information from the EPA, please visit EPA’s Actions on Ethylene Oxide webpage.  

What is DHEC doing to address the concerns of EtO? 

DHEC is partnering with the EPA, communities, and other stakeholders to further identify and evaluate the sources of EtO emissions in South Carolina. The department’s efforts include: 

  • Completed an initial round of air sampling in November 2019 in several communities where elevated health risks have been estimated based on the 2014 NATA 
  • Collected background samples in October 2019 to provide information about the presence of EtO in locations away from known sources 
  • Conducting additional sampling at the National Air Toxics Trends Station site in Chesterfield in mid-2020 
  • Working with local communities to share information and data 
  • Educating the public about the known estimated health risks  

Unknowns about EtO

There are still many unanswered questions regarding EtO, and the risk of exposure to low levels of EtO is not well understood. The EPA and state health agencies are working together to find answers to questions such as: 

  • What are the sources of EtO that’s been found away from known industrial sources? 
  • How do the ambient levels of EtO vary nationally and seasonally across the country? 
  • How can methods used to monitor for EtO be improved? 
  • How long does EtO persist in the atmosphere? 
  • What is its involvement in atmospheric chemistry and transport? 
  • What are the best methods for measuring EtO in real-time and/or in source streams? 
  • What are the next steps if the presence of EtO is confirmed to be everywhere? 

Total emissions of air toxics are declining nationwide, and air quality monitoring data show that concentrations of many toxics in the air are also trending downward.  Many air toxics emissions have declined significantly since the EPA compiled the data for 2014 NATA. The EPA is currently preparing the next assessment based on 2017 emissions. For more information related to the 2014 NATA, please see EPA’s 2014 NATA Fact Sheet.     

For more information, please contact Rhonda Thompson, Chief, Bureau of Air Quality by email or (803) 898-4391