Probabilistic human health risk assessment for quarterly exposure to high chloroform concentrations in drinking-water distribution network of the Province of Quebec, Canada.
Because quarterly concentrations of total trihalomethanes (THM) exceeding the 80 μg/L guideline are often tolerated by the public health authorities of the Province of Quebec (Canada), this study examined whether quarterly episodes of high concentrations of THM may pose a risk to the health of its population. Using Monte Carlo simulations, a probabilistic risk assessment was performed for infants (0-<6 mo), toddlers (6 mo-<5 yr) and adults (≥20 yr). Multiroute exposure including ingestion of drinking water as well as inhalation and dermal exposure while showering or bathing was considered. The resulting absorbed doses were compared to short-term reference values for chloroform, used as surrogate for THM, by calculating risk quotients (RQ). On the basis of THM concentrations values in Quebec's drinking water distribution systems during the months of July to October and exceeding the guideline value (>80 μg/L), the 95th percentile value of RQ were 0.65, 0.46, and 0.24 for infants, toddlers, and adults, respectively. Back-calculation allowed determining that a chloroform concentration of 330 μg/L would result in RQ ≤ 1 for 99% of infants, the subgroup considered the most susceptible among the general population. Overall, this study showed that episodes of high THM concentration encountered in Quebec drinking-water distribution network need not be considered as an immediate health concern for the general population. However, these results should not be interpreted as an authorization to exceed the 80 μg/L standard but rather as a risk management tool for public health authorities.
Institut national de santé publique du Québec, Montréal, Québec, Canada.
Stephane
S
Buteau
Mathieu
M
Valcke
D001494:Baths; D002675:Child, Preschool; D002725:Chloroform / Q000009:adverse effects / Q000032:analysis; D004326:Drinking; D004781:Environmental Exposure / Q000009:adverse effects / Q000032:analysis; D004784:Environmental Monitoring; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D019570:Inhalation Exposure; D009010:Monte Carlo Method; D011634:Public Health; D011792:Quebec; D018570:Risk Assessment; D022882:Trihalomethanes / Q000009:adverse effects / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000009:adverse effects / Q000032:analysis*; D014876:Water Pollution / Q000009:adverse effects / Q000032:analysis; D014881:Water Supply; D055815:Young Adult
D022882:Trihalomethanes; D014874:Water Pollutants, Chemical; D002725:Chloroform