The High Council for Public Health (HCSP) points out that trihalomethanes (THM) concentrations are generally higher in water intended for human consumption produced from surface water than in water intended for human consumption produced from groundwater. Significant disparities in exposure (through ingestion, inhalation and skin contact) to THMs linked to different uses of water intended for human consumption in the home have been observed in France. In terms of health effects, epidemiological studies conclude that there is a link between exposure to THMs and certain types of cancer. Toxicological studies associate exposure to high levels of THMs with effects on reproduction.

The HCSP emphasizes that, for distribution units facing recurrent episodes of non-compliance with THM levels in water intended for human consumption, it is essential to reduce THM precursors from the source to the points of use concerned, with an understanding of existing spatial and temporal variations and the implementation of optimizations in the drinking water treatment process.

Considering the different types of exposure associated with the use of water intended for human consumption in the home, in the event of periods when the quality limit is exceeded, the HCSP recommends that pregnant women and infants consume bottled water. 

The HCSP notes that aerating water in wide-necked glass jugs can reduce the concentrations of certain THMs, but there is no guarantee that the levels will fall below the quality limit. It recommends renewing the ambient air in washrooms and bathrooms, and indicates that reducing exposure through skin contact, although this cannot be quantified, is linked to reducing the amount of time spent in direct contact with water while showering and bathing.