62. Assessing the Relation between Plasma PCB Concentrations and Elevated Autistic Behaviours using Bayesian Predictive Odds Ratios (lay summary)

Bernardo BA, Lanphear BP, Venners SA, Arbuckle TE, Braun JM, Muckle G, Fraser WD, McCandless LC. International Journal of Environmental Research and Public Health. 2019 Feb 5;16(3). pii: E457. doi: 10.3390/ijerph16030457.

Autism spectrum disorder (ASD) is a neurodevelopmental condition affecting 1-2% of children, that is characterized by impaired social communication and repetitive or stereotypic behaviours that appear during early childhood. It has been suggested that maternal exposure to some environmental chemicals during fetal development may play a role in the onset of ASD. In particular, the first and third trimesters of pregnancy have been identified as important developmental windows for chemical exposure. One class of chemicals, polychlorinated biphenyls (PCBs) have well-established neurotoxic effects, and as a result, have been banned in Canada since the late 1970s. Still, PCBs continue to persist in the environment and the effects of low-level PCB exposure on ASD remains unclear.

The aim of this study was to examine the relation between blood PCB concentrations measured during the first trimester of pregnancy and increased autistic behaviour in 3 to 4 year old children. Data were analysed from 546 mother-infant pairs from the MIREC study. At age 3-4 years, caregivers completed a questionnaire that measured the social ability and behavioural characteristics of the child during the previous 6 months. The sum of the questions gives a total score; higher scores are more likely to indicate ASD behaviors.

No decisive evidence was found of an association between blood PCB concentrations and autistic behaviour score. However, the study found small but imprecise increases in the mean score and risk for more autistic-type behaviour in the children whose mothers had the highest PCB concentrations in their blood compared with those with the lowest category.

In conclusion, this is one of few studies that have examined prenatal PCB exposure and autistic behaviour in children.  Further research is needed to improve our understanding of the possible effects, if any, of chemical mixtures and combined exposure to multiple PCBs on risk of autistic behaviors in children.