Phthalates, used as plasticizers in many plastics including polyethylene, polypropylene and more, have been associated with endocrine disruption. But, given their ubiquity in the environment, it is challenging to really pinpoint exposure in humans. Phthalates are metabolized in the body into monophthalate ester metabolites and excreted in urine. So, measuring these phthalate ester metabolites in urine can provide a sensitive and representative marker of exposure.
In an article published in Nature’s Journal of Exposure Science and Environmental Epidemiology, a team of researchers for the Canadian Healthy Infant Longitudinal Development (CHILD) study characterized phthalate exposure in infancy and early childhood, trends by age, and factors that influenced concentrations. SGS AXYS measured eight metabolites of six common phthalates in 1578 3-4 month old infants all over Canada using our custom enzymatic-deconjugation, isotope dilution LC-MS/MS method. The method provides sensitive and selective analysis of critical phthalate ester metabolites indicative of phthalate exposure.
|Targets (Reporting limits < 1 ng/mL)|
|Monomethyl phthalate (mMP)|
|Monoethyl phthalate (mEP)|
|Monobutyl phthalate (MBP) (sum of mono-n-butyl and mono-iso-butyl phthalate)|
|Monobenzyl phthalate (mBzP)|
|Mono-2-ethylhexyl phthalate (mEHP)|
|Mono-(2-ethyl-5-oxohexyl) phthalate (DEHP Metabolite VI) (mEOHP)|
|Mono-(2-ethyl-5-hydroxyhexyl) phthalate (DEHP (Metabolite IX) (mEHHP)|
|Mono-cyclohexyl phthalate (MCHP)|
|Mono-(3-carboxypropyl) phthalate (MCPP)|
|Mono-iso-nonyl Phthalate (MiNP)|
Except for one low abundance metabolite (mono-methyl phthalate or MMP), most metabolites were detected in over 70% of samples, indicating good method sensitivity and coverage. Levels in children increased with age from 3-36 months. Interestingly, socioeconomic status (SES) was the largest predictor of phthalate levels in infants. Concentrations of all metabolites were higher in the lowest income categories, except for MEHP at 3 months, among children with any breastfeeding at 12 months. Researchers noted that the type of home correlated quite strongly with phthalate levels as well with apartment residents showing higher levels. More study is needed and this work is part of a larger investigation into this important exposure issue.
“CHILD is the largest multidisciplinary, longitudinal, population-based birth cohort study in Canada and is designed to be one of the most informative studies of its kind in the world”. The CHILD study does amazing work following a group of more than 3400 children as they grow and uses an array of genetic, epigenetic, exposure measurement and other tools to assess causes of chronic illnesses in children.