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French Agency for Food, Environmental and Occupational Health & Safety

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Updated on 26/07/2017

Biological limit values for chemicals used in the workplace

Expert appraisal necessary for defining biological exposure limits for chemicals used in the workplace

Keywords : Occupational exposure limit values (OELVs), Chemical risks

Determining occupational exposure limits for chemicals requires different but complementary approaches that may involve measuring substances in the atmosphere of the work environment, measuring surface contamination of workstations and biomonitoring of workers, in other words monitoring biological markers which reflect worker exposure. Consequently, whenever ANSES considers it to be relevant, it may, in addition to atmospheric OELs, propose biological limit values which could be used for biological monitoring of exposure by occupational physicians.

Biological monitoring consists in measuring biological exposure markers, in the biological matrices (tissue, excretions, secretions or exhaled air) of workers exposed to chemicals. The latter could be:

  • the toxic substance itself;
  • one or more of its transformation products or metabolites.

Biological indicators of early and reversible effects (for instance, urinary excretion of proteins indicating a kidney disorder) are likely to complement this monitoring for some chemicals to the extent that they may be specifically correlated to exposure to these substances.

Depending on the nature of the toxic substance and its fate in the body, the exposure dose reflects recent or chronic exposure.

The key characteristic of biological monitoring is that it can include all of the routes through which a substance enters the body (inhalation, penetration through the skin, ingestion) and exposure sources (food, occupational, environmental). On the contrary it cannot be used to distinguish between the contribution of different routes and exposure sources, nor can it identify exposure peaks.

The biological limit values are recommended by ANSES as biological exposure markers which are considered to be relevant in the workplace. They are intended to protect workers from harmful effects related to exposure to the chemical in question, over the medium- or long-term. They take into account repeated exposure throughout a worker's working life.

How does ANSES define these values?

The recommended biological limit values do not all have the same significance, as this depends on the available data:

  • if the corpus of scientific data is sufficient to enable precise quantification of a dose/response relationship, then the biological limit values will be defined on the basis of health data (lack of effect for substances at a given threshold or risk levels for carcinogenic substances with no threshold);
  • if no such data is available for substances with a threshold effect, the biological limit value will be calculated on the basis of the expected concentration of the biological exposure marker when the worker is exposed to the 8h-OEL. For no threshold carcinogenic substances, if there are insufficient quantitative data, then a biological limit value will be defined on the basis of another effect (pragmatic biological limit value). This pragmatic value is not intended to recommend a value below which there is no health risk but aims to limit exposure to these substances in the workplace.

Whenever possible, ANSES also recommends biological reference values (BRV). These correspond to concentrations found in a general population of adults whose characteristics are similar to those of the French population (preferentially for the biological indicators of exposure) or, by default, in a non-worker control population exposed to the substance being studied (preferentially for the biological indicators of effects).

Biological reference values (BRV), that cannot be regarded as protecting from the onset of health effects, nevertheless allow a comparison to be made with concentrations of biological indicators of exposure measured in exposed workers. These values are particularly useful when a biological limit value (BLV) cannot be determined.