Integrated risk assessment – radiation and chemicals

Occupational workers work in an environment where there are mixed pollutants, some of them are cancer-causing and some may cause non-cancer diseases. For worker’s overall safety considerations, it may become necessary to assess health risks from individual pollutants, as well as combined risk from all the pollutants existing in the work environment. The pollutants may include chemicals, radiation, physical pollutants, etc.

Health effects of radiation or chemicals are classified as acute or chronic. Acute affects results from a single exposure to a high radiation dose rate or exposure to a high concentration of a chemical. The effect, deterministic in nature sets in rapidly and could be mild to severe. The dosage of chemicals or radiation plays a significant role in the level of severity of the effect. Chronic effects develop over a long period of exposure to a low concentration of chemical or low dose rate of radiation. The effect may remain invisible for a relatively long period, called the latent period. Carcinogenicity is included in chronic effects, which are stochastic in nature.

 For a given end-point, say cancer, the risk from the exposure/intake may be added to get an integrated risk, which may be expressed in terms of the risk equivalent radiation dose. As of now, ICRP assumes a total lifetime stochastic risk of 0.01 per Sievert of radiation dose received as tolerable. This is in the absence of ALARA.

An integrated risk assessment system needs to be in place to have an overall risk perspective for the benefit of policymakers and decision-makers to try to achieve risk reduction of the workers in totality – from radiation as well as chemicals. Thus, the total detriments will have different components. Once the risk from exposure to all the pollutants is quantified for a given end-point by some acceptable methodology, it can be expressed in terms of Risk Equivalent Radiation Dose (RERD).

Dose reductions for radiological safety in occupational scenarios can consider the risk of both the radiation and possible presence of chemical pollutant in the work environment. Similarly, environmental safety should take into account the ambient levels of chemical pollutants and the corresponding risk to the members of the public. 

Additional small contributions to the environmental pollution by the discharges from nuclear industry cause negligible risk as compared to the multiple chemicals risks, as seen by the calculated RERD values.

[More details, references in Harmonization of Risk Management Approaches-Radiation and Chemical Exposures, Pushparaja, and P. Srinivasan, Proc. IRPA 11, Madrid, Spain, 2011].