70. Perchlorate in human milk samples from the Maternal-Infant Research on Environmental Chemicals study (MIREC) (lay summary)

Wang Z, Sparling M, Wang KC, Arbuckle TE, Fraser WD. Food Additives and Contaminants, Part A Chemistry, Analysis, Control, Exposure & Risk Assessment. 2019 Sep 25:1-10. doi: 10.1080/19440049.2019.1668968

Perchlorate is a compound that occurs naturally in the environment, primarily near potash deposits. It may be present in air, soil, and water because of its use in military and industrial products such as solid rocket fuels, explosives and fireworks, and some fertilisers. Perchlorate can disrupt thyroid hormones that are responsible for regulating metabolic and developmental functions critical for normal fetal and infant development. Consequently, pregnant women and their fetuses, infants, and people with iodine deficiency or with thyroid dysfunction are particularly at risk from elevated perchlorate exposure.

The aims of this study were to develop a sensitive laboratory method and then measure perchlorate in human milk samples collected from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study.

A total of 439 human milk samples were analysed.  Perchlorate was detected in most of the milk samples.  There was no difference in average perchlorate levels by woman’s age or whether she had a previous life birth.  No association was observed between perchlorate levels in breast milk and the woman’s thyroid hormone levels during pregnancy.

This project provided important information on perchlorate levels in human milk collected from MIREC participants from across Canada.  The milk data were used to estimate dietary exposure for infants less than 1 year old and infants 1 to 3 years of age.   Neither of these estimates exceeded the United Nations and World Health Organization provisional maximum tolerable daily intake of 10 μg/kg bw/day.