75. Gestational Exposures to Phthalates and Folic Acid, and Autistic Traits in Canadian Children (lay summary)

Oulhote Y, Lanphear BP, Braun JM, Webster GM, Arbuckle TE, Etzel T, Forget-Dubois N, Séguin JR, Bouchard MF, MacFarlane AJ, Ouellet E, Fraser WD, Muckle G. Environmental Health Perspectives 2020 Feb;128(2):27004. doi: 10.1289/EHP5621

Phthalates are a group of chemicals used in plastics to soften and increase flexibility.  They can also be used as solvents in a number of consumer products including cosmetics, fabrics, paints, printing inks, children’s toys, and non-prescription drugs.  Some phthalates are commonly detected in urine of Canadians, while others are less commonly detected.

Autism Spectrum Disorder is a developmental disorder that impacts how a person perceives and socializes with others, causing problems in social interaction and communication. The disorder also includes limited and repetitive patterns of behavior.  Symptoms generally appear in the first two years of life.  It is estimated that 1 in 66 Canadian children and youth (ages 5-17) are diagnosed with Autism Spectrum Disorder.  The causes of autism are poorly understood, but scientists believe that multiple factors can lead to autism.  Only a few studies have examined the potential association between exposure to phthalates and autistic behaviors.

The goal of this study was to examine the association between prenatal exposure to several phthalates and autistic behaviors in 3- to 4-year old children in the MIREC Study.  While this study did not diagnose autism in the children, it did use the Social Responsiveness Scale (SRS) assessment to measure behaviors that have been associated with autism.

Phthalates were measured in first trimester urines of women participating in the MIREC study.  Information on whether mothers took dietary supplements containing folic acid was obtained by questionnaire during the pregnancy.  As part of the MIREC-CD Plus Study, at 3 to 4 years of age, 601 children were assessed for autistic behaviors using the SRS.

The study found that boys whose mothers had higher levels of two phthalates (mono-n-butyl and mono-3-carboxypropyl) in their 1st trimester urines had higher SRS scores, indicating poorer social communication and restricted interests and repetitive behaviors.  The researchers also found that associations between several phthalates and autistic traits were only apparent in children of women who had low prenatal folic acid supplementation (< 400 µg/day).

In conclusion, this study found that higher maternal urinary levels of some phthalates were associated with more behaviors associated with autism in boys.  However, these small effects were reduced if the mother took folic acid supplements during pregnancy.  These results agree with earlier research showing increased susceptibility of the developing brain, especially the male fetal brain, to the impact of toxic chemicals. Finally, these results provide further evidence of the potential opportunities for primary prevention of ASD by reducing exposures to environmental toxicants and ensuring adequate folic acid supplementation early in pregnancy.