Guidance for Air
The following guidance was developed by the Minnesota Department of Health (MDH) in 2013 in response to vapor intrusion investigations conducted with the Minnesota Pollution Control Agency (MPCA). For the supporting information used to derive this guidance, please contact the Site Assessment and Consultation Unit or refer to the document Trichloroethylene (TCE) in Air (PDF).
Trichloroethylene: Risk Assessment Advice for Air
December 31, 2013
Chemical: Trichloroethylene (TCE)
CAS Number: 79-01-6
Endpoint: Immune system, cardiac development, cancer
Chronic Value: 2 µg/m3
Sources: US EPA, 2011
The Minnesota Department of Health (MDH) prepared this guidance to evaluate the health risks from breathing Trichloroethylene (TCE). This advice can be used to evaluate risks from contaminated air inside or outside of the home. Sources of TCE air contamination include dry cleaning and household products. TCE can also move from contaminated groundwater into the soil and into the air in homes (“vapor intrusion”).
MDH Risk Assessment Advice (RAA) for TCE in air is a level of 2 micrograms TCE per cubic meter of indoor air (2 μg/m3). A concentration of 2 μg/m3 is considered safe to breathe 24 hours a day during any period of life, or over an entire lifetime. MDH considers 2 μg/m3 protective for potentially sensitive populations, such as young children or pregnant women. No public health actions to reduce exposures are necessary or recommended when TCE concentrations in air are at or below this level.
Basis of the TCE air value
The value of 2 μg/m3 was developed by the U.S. Environmental Protection Agency (US EPA) in 2011 and is recommended by MDH for use in Minnesota. The number is based on data from animal and human TCE studies. US EPA chose the animal studies that showed health effects at the lowest exposure concentrations. One study showed an increased risk of subtle immune system impacts (decreased thymus weight) and another study showed heart malformations in animals born to mothers exposed during pregnancy.
The results of these rodent studies were adjusted to take into account differences between animals and humans. Adjustments included the possibility that people are more sensitive to TCE than laboratory animals. The resulting air value (2 μg/m3) is much lower than the levels of TCE exposure in the rodent studies.
According to the US EPA assessment, daily exposure to 2 μg/m3 or less protects the population from cancers that are associated with higher exposures to TCE.
The air value of 2 μg/m3 is not expected to harm people over a lifetime of exposure. Breathing in TCE just above 2 μg/m3 does not mean that health effects will occur. It is not known what precise level in air will affect any particular person.
Change from previous advice for TCE in air
Neither MDH nor US EPA have developed a one hour limit to replace the acute HRV. The acute HRV is a promulgated rule that is removed or replaced through rulemaking. The HRV remains available for risk management purposes, similar to situations that lead to dual guidance for drinking water.
Follow the links on the air values table (in the table header) to understand exposure durations and the difference between Risk Assessment Advice and other types of guidance that MDH publishes.
US EPA (2011). EPA Integrated Risk Information System, Trichloroethylene, 09/28/2011.http://www.epa.gov/iris/subst/0199.htm#refinhal, accessed December 30, 2013