85. Urinary phthalates and body mass index in preschool children: The MIREC Child Development Plus study (lay summary)

Ashley-Martin J, Dodds L, Arbuckle TE, Lanphear BP, Muckle G, Foster WG, Ayotte P, Zidek A, Asztalos E, Bouchard MF, Kuhle S. International Journal of Hygiene and Environmental Health Int J Hyg Environ Health. 2021 Mar;232:113689. doi: 10.1016/j.ijheh.2021.113689

Phthalates are a class of chemicals commonly used to soften or increase flexibility of plastics found in food packaging, toys, and personal care products.  Children are exposed to phthalates on a regular basis in their day to day lives.  Phthalates may disrupt the endocrine system in growing children and there is some evidence that these chemicals may be ‘obesogens’ (chemicals that may contribute to obesity).  Children are rapidly growing and may be more vulnerable to chemical exposure than adults. It is, therefore, particularly valuable to understand if chemicals, such as phthalates, could affect child growth and development.

Little is known about how early life exposure to this class of chemicals might affect children’s body mass index (BMI) (a measure of body fat based on height and weight).  There is also little known about whether phthalate exposure might affect boys and girls differently.

To address these questions, researchers at Health Canada used data from the MIREC study to investigate the impact of phthalate exposure during early childhood on BMI. The researchers measured 22 phthalate metabolites in children’s urine.  When people are exposed to phthalates, their body changes the chemicals and excretes the breakdown products – or metabolites – in urine.  Measuring these metabolites in urine is a way for scientists to estimate how high or low children’s exposure levels are. Researchers measured children’s BMI and collected urine samples at the same time. Statistical models were used to calculate the association between urinary concentrations and BMI.

Approximately 200 children between the ages of two and five were included in this study.  The researchers found 18 of the 22 phthalate metabolites were detectable in more than 80% of urine samples.  They also reported children with higher levels of the phthalate DnBP tended to have, on average, moderately higher BMI levels than those children with the lowest levels of DnBP.  The researchers did not find any differences between boys and girls.

In conclusion, exposure to DnBP, a common phthalate found in food packaging, may be associated with higher BMI in preschool aged children.  Two of the limitations of this research however, are that phthalates were only measured at one point in time and were measured at the same time as the BMI.  Phthalates do not persist for a long time in the environment or in humans so one measure presents a single snapshot of exposure rather than an estimate of average exposure over time. As a result, this study cannot draw any conclusions about whether higher exposure to some phthalates in young children causes obesity.   It will be interesting to see if research studies that measure phthalates at multiple time points prior to measurement of BMI find similar results.