Cumulative Health Risk from Exposure Load (CHREL): Looking at multi-chemical exposures through the lens of biomonitoring guidance values

Exposure load (EL) is an indicator of multiple chemical exposures based on human biomonitoring data. We used EL methodology and human biomonitoring health-based guidance values (HB2GVs) as exposure thresholds to create a new metric called Cumulative Health Risk from Exposure Load (CHREL). HB2GVs are derived by calculating the concentration of a biomarker consistent with a health protective exposure guidance value. CHREL analysis was conducted using Canadian Health Measures Survey (CHMS) cycle 3 and 4 biomonitoring data. Based on 18 chemicals, more than half of the Canadian population had an estimated CHREL_TOTAL of 1 or more, indicative of chemical exposures potentially above selected exposure guidance values. Females had a significantly lower CHREL_TOTAL compared to males, 12-19 year olds had a lower CHREL_TOTAL compared to older age groups (significant compared to 40-59 year olds), and nonsmokers had a significantly lower CHREL_TOTAL than smokers. Small segments of the population had a CHREL_LIVER or a CHREL_NERV of 1 or more, indicating exposures potentially above guideline levels for chemicals affecting the liver or nervous system. CHREL_CANC was calculated based on 6 chemicals with HB2GVs derived for cancer endpoints. At the 10^-5 risk level, most people had an estimated CHREL_CANC of 3, indicative of multiple chemicals that may exceed negligible cancer risk. The most important contributors to exposures above HB2GVs were inorganic arsenic, mercury, acrylamide, xylenes, benzene and triclosan. Keeping certain assumptions, uncertainties and limitations in mind, the CHREL indicator can be used to obtain a picture of potential cumulative health risks from combined chemical exposures in a population, and as a comparative measure between subpopulations, including vulnerable subgroups.