Perchlorate ions: ANSES's studies and recommendations
During the national measurement campaign conducted in 2011 by ANSES's Laboratory for Hydrology, perchlorate ions were detected in water intended for human consumption (WIHC) in several regions of France. These ions interfere with iodine absorption by the thyroid, one of the initial stages in thyroid hormone synthesis. At the request of the Ministry of health, ANSES has conducted a health risk assessment of the presence of perchlorate ions in WIHC and in milk formulas for infants aged 0 to 6 months, the most vulnerable population group. With regard to the calculated exposure levels, ANSES concluded that the risk of surpassing the toxicity reference value set by the Agency in 2011 cannot be excluded for certain infants. Consequently, ANSES recommends lowering perchlorate ion concentrations in infant milk formulas, and in cases where tap water is found to have perchlorate ion levels higher than 4 µg/L, it suggests that the authorities inform the public and recommend limiting tap water consumption by children under 6 months of age.
The presence of perchlorate ions in water for human consumption was reported in 2011 in the Aquitaine and Midi Pyrénées regions, in areas that manufacture ammonium perchlorate for civilian (aeronautics) and military (pyrotechnic products) uses; in fact, ammonium perchlorate has numerous industrial applications, especially in the military and aerospace fields. Other possible local sources of contamination (natural sources, Chile saltpetre,impurities in industrial hypochlorite solutions used for water disinfection) have been excluded.
In humans, perchlorate ions inhibit iodine absorption in the thyroid, thus interfering with the synthesis of thyroid hormones, and anopinion on the health risks of perchlorate ions in WIHC was published by ANSES in 2011.
In this opinion, ANSES proposes a toxicity reference value (TRV 0.7 µg/kg bw/d) and a guideline value for drinking water (15 µg/L). This TRV, based on early biological effects, was proposed in order to account for the most susceptible populations (in particular pregnant women, newborn infants and children under six months of age). Based on this value, the Directorate General for Health (DGS) established two management guideline levels: 15 µg/L for adults and 4 µg/L for children under six months of age.
Drafting of a national map of perchlorate ion contamination of the water supply and a study on milk
In the wake of the 2011 opinion, ANSES's Nancy Laboratory for Hydrology conducted a sampling and analysis campaign for perchlorate ion contamination of the water supply and of WIHC. To do this it produced a country-wide map representing 25% of the water produced in France. Analyses were also made of samples of bottled water marketed in France.
In addition, since children under six months of age are a population which is vulnerable to the effects of perchlorate ions, ANSES in conjunction with the DGCCRF conducted a sampling plan to measure perchlorate ion levels in infant formulas marketed in France.
Together, the data on WIHC and infant milk formulas were used by the Agency to calculate the exposure to perchlorate ions in children under six months and to assess the health risk with regard to the TRV established by the Agency in July 2011.
Results
The Nancy laboratory's sampling and analysis campaign found perchlorate levels of under 0.5 µg/L in three-quarters of the 703 samples analysed. The perchlorate ion was found in groundwater, in the Nord-Pas-de-Calais region in particular, where the origin of the contamination was identified. A link between the presence of perchlorate and the First World War has been assumed, although a possible contribution from certain industrial activities in the region cannot be excluded.
Situations where the management level of 4 µg/L is exceeded exist in approximately 2% of water treatment and production facilities, mainly located in the Nord-Pas-de-Calais region. This national campaign showed that no water treatment or production facilities exceeded the management level of 15 µg/L, applicable to the adult population.
The results of the surveillance plan set up in 2012 to measure perchlorate ion levels in infant formulas available on the French market showed that infant and follow-up milks reconstituted with perchlorate-free water intended for children under six months contained average levels of 1.8 µg/L and 2.8 µg/L respectively and maximum levels of 8.7 µg/L and 10.2 µg/L respectively.
However, when the water used for the reconstitution of milk for baby bottles contains perchlorate ion levels of over 2 µg/L, an exceedance of the TRV may occur in 5% of children under six months of age.
ANSES's recommendations
In view of the results obtained, the Agency recommends:
- that manufacturers reduce perchlorate ion levels in infant formulas marketed in France;
- that, due to the lack of information on the origins of perchlorate ion contamination in infant formulas, further investigations into contamination sources be made;
- pursuing investigations into the origins of water contamination;
- informing populations whose drinking water has perchlorate ion levels above 4 µg/L, and recommending limited consumption of this water by children under six months of age.
Nutritional iodine intake is a key factor in assessment of the health impact of perchlorate ions in humans. In fact, an iodine deficiency increases the probability that perchlorate ions will have an effect on the thyroid gland. Therefore, the Agency recommends gathering updated data on iodine intake in pregnant and breastfeeding women as well as in children under three.
Other work in progress or to come
Measurements of perchlorate ion concentrations in fruits and vegetables are currently being taken, since these foods can also be a source of exposure to these substances. This could lead to conducting food exposure assessments in children and adults.
In addition, the InVS is conducting epidemiological studies in the Nord-Pas-de-Calais region in order to detect possible links between perchlorate ion levels in water and the thyroid-stimulating hormone (TSH) levels measured in newborns as part of a systematic congenital hyperthyroidism screening process.