Differences in mirex [dechlorane] and dechlorane plus [syn- and anti-] concentrations observed in Canadian human milk.

Rawn DFK, Quade SC, Corrigan C, Ménard C, Sun WF, Breton F, Arbuckle TE, Fraser WD. Chemosphere 2023 Jan 6;316:137784. doi: 10.1016/j.chemosphere.2023.137784

There are a number of chemicals that persist in the environment and can be found in our bodies. Two such chemicals are mirex (dechlorane) and dechlorane plus. Mirex was widely used to control fire ants and other insects in other parts of the world but was not used as an insecticide in Canada. Mirex was also added as a flame retardant in paints, electrical goods, plastics and rubber between 1959 and 1972. Following the removal of most uses of mirex as an insecticide in the US in the late 1970s, due to toxicity concerns, other highly chlorinated compounds were developed as replacement flame retardant products, including dechlorane plus, which is used in electronics, wires and roofing materials.

Dechlorane plus has been measured in household dust. Few studies have attempted to measure mirex and dechlorane plus in human milk.

Researchers at Health Canada analysed samples of human milk collected from MIREC participants for these two chemicals.

Mirex was detected in all samples analyzed (n = 298), while forms of dechlorane plus were present in 61.0% to 79.5% of the samples (n = 541). Mirex concentrations have declined in human milk since the 1990s.

Since this is the first pan-Canadian study reporting dechlorane plus concentrations in human milk, no time trend comparisons can be made. Maternal age was weakly, but positively correlated with concentrations of both chemicals, while parity (the number of pregnancies of at least 6 months duration) did not impact concentrations of either chemical.

Given the presence of this relatively recently identified flame retardant (dechlorane plus) in human milk from women across Canada, studies to identify major sources of exposure to this chemical are needed.

Despite low concentrations of environmental chemicals in human milk from Canadian women, Health Canada supports breastfeeding of infants because of the important health benefits to both the mothers and their infants. Breast milk has the perfect amount of protein, carbohydrate, fat, vitamins and minerals for a growing baby. It’s the easiest milk for a baby to digest. Breast milk contains antibodies and other immune factors that help protect the baby against infections and disease.

Back to list