ANSES proposes new toxicity reference values (TRVs) for two substances, vinyl chloride and cadmium07 August 2012

For several years, ANSES has been running a national programme for evaluation of toxicity reference values (TRVs) within the context of its TRV scientific expertise missions.

Today ANSES publishes new values for two contaminants frequently found in the environment:

• vinyl chloride monomer, whose main source is the production of PVC (polyvinyl chloride) plastic. Another major source of exposure is the microbiological degradation of perchloroethylene (PCE), trichloroethylene (TCE) and cis- and trans-dichloroethylene (DCE) (used in degreasing, surface treatments and dry cleaning) through anaerobic dehalogenation in the soil and in ground water. The microbiological degradation of these compounds produces vinyl chloride under the ground, which in the form of fumes (soil gas) enters the ambient air and water sources;
• cadmium and its compounds: cadmium is a heavy metal used in industry which is found mainly as an oxide, chloride, sulphate, nitrate or sulphide. Cadmium oxide (CdO) can be found in the atmosphere in the form of dust or fumes. Cadmium is also found in cigarette smoke in the form of minute particles of cadmium oxide which settle mainly in the pulmonary alveoli.

These two compounds have been classified as "carcinogenic to humans" (Group 1) by the International Agency for Research on Cancer (IARC). The creation of these two TRVs is a specific response to the goals set by the French National Environment and Health Action Plan (PNSE 2) and the Cancer Plan.

Based on the collective expert assessment of all the available scientific data on the toxicity of these compounds and on their carcinogenic effects to humans and animals in particular, the Agency proposes:

for vinyl chloride monomer:

• a chronic TRV of 0.625 (mg\kg\d)-1 for oral-route carcinogenic effects based on animal data;
• a chronic VTR of 0.0038(mg\m3)-1 for respiratory-route carcinogenic effects based on animal data.

for cadmium and its compounds:

• a chronic VTR of 0.3 _g.m-3 for respiratory-route carcinogenic effects based on animal data;
• a chronic VTR of 0.45 _g.m-3 for non-carcinogenic respiratory-route effects based on human data.

What is a toxicity reference value (TRV)?

A TRV is a toxicological index used to establish a qualitative and quantitative relation between exposure to a chemical substance and an adverse health effect in humans. There are TRVs with and without a "dose threshold".
TRVs with a dose threshold correspond to substances which cause damage above a certain dose and whose severity is proportional to the dose absorbed.
TRVs without a dose threshold are set for substances for which there exists a probability (even a minute one) that a single molecule penetrating the body may cause harmful effects.

TRVs are established for a given substance based on a critical effect and are specific to a given exposure duration (acute, subchronic or chronic) and exposure route (oral, respiratory, etc.). The proposal of a TRV, which serves to establish a link between hazards and exposure to a toxin, is an essential step in the health risk assessment process (ICPE regulations, prevention, local management of a declining situation).