Oulhote Y, Tremblay E, Arbuckle TE, Fraser WD, Lemelin JP, Séguin JR, Ouellet E, Forget-Dubois N, Ayotte P, Boivin M, Dionne G, Lanphear BP, Muckle G. Environment International. 2018 Oct;119:79-88. doi: 10.1016/j.envint.2018.06.010
Polybrominated diphenyl ethers (PBDEs) are man-made chemicals that were once widely applied to materials to resist fire. In 2008, the Canadian government restricted the manufacture and use of PBDEs. But Canadians are still exposed to these toxic chemicals because they persist in the environment for years. PBDEs are commonly found in electronic equipment, plastics, and clothing. Humans are exposed to PBDEs in some foods, indoor air and indoor dust. PBDEs can also be passed from pregnant mothers to their developing babies through the placenta. Some research suggests that exposure to higher levels of PBDEs during pregnancy may negatively affect a child’s cognitive and behavioural functions. No study has looked to see if exposure to higher PBDEs during pregnancy is associated with changes in behaviour at early stages, such as infancy. One early indicator of potential childhood behavioural problems is the infant’s temperamental reactivity and response to frustration, as measured by the arm restraint test. This test provides a measure of an infant’s tendency to show frustration, which is thought to be a predictor of poor social-emotional and psychological functioning in later childhood.
This research was conducted using data from the MIREC Study. The aim was to examine the relationship between exposure to PBDEs during pregnancy and predisposition to frustration among Canadian infants. Maternal blood samples from the first trimester of pregnancy for 333 women were analysed for PBDE concentrations. Infants of these mothers participated in the arm restraint test when they were around 6-7 months old. The infants’ arms were gently held down at their sides and the test ended after 2 minutes or if the infant cried for 20 seconds. Several measures were taken from the test, including how long it took for the infant to cry or scream (if at all), the duration of crying, as well as the infants’ movements during the test, such as stretching their legs.
Infants who were exposed to higher (vs. lower) levels of some PBDEs were more likely to cry or scream, and tended to do so more quickly during the test. One interesting finding is that exposure to PBDEs was related to the infants’ movements during the test, but that this was different for boys and girls. Among girls with higher levels of PBDEs, movements during the arm restraint test tended to be more extreme – that is, either no movement or heightened movement, compared to a moderate amount of movement. Among boys with higher levels of PBDEs, movements during the arm restraint test tended to be more moderate, and less extreme.
In this group of Canadian women and their infants, exposure to some PBDEs during pregnancy was associated with infants’ tendency towards frustration. Future work, using data from the MIREC study, will confirm if this tendency to frustration ultimately leads to behavioural problems in later childhood.