Association of urinary polycyclic aromatic hydrocarbon metabolites with symptoms among autistic children: A case-control study in Tianjin, China.
Urine PAH levels rise with autism severity — add environmental questions to your assessment checklist.
01Research in Context
What this study did
Li et al. (2022) compared urine from autistic and neurotypical children in Tianjin, China.
They measured breakdown products of polycyclic aromatic hydrocarbons — chemicals from car exhaust and grilled food.
Higher levels of these PAH markers were linked to autism diagnosis and to higher scores on the CARS and ABC checklists.
What they found
Kids with ASD had more PAH waste in their urine than matched controls.
The more PAH waste, the more severe the autism behaviors parents and clinicians reported.
How this fits with other research
Stein et al. (2015) saw the same pattern with bisphenol A: autistic kids excreted more.
Mulder et al. (2020) looked at PCBs in Jamaican children and found the opposite — lower blood levels were tied to ASD. The diets and pollution sources differ, so both findings can be true.
Rojahn et al. (2012) hunted urinary porphyrins and found high levels in ASD, but the test missed most cases. PAHs may act the same way: useful flag, not a stand-alone diagnostic.
Why it matters
You can’t change the past, but you can ask about air-quality, smoking, and diet during intake. If a child’s autism behaviors spike, checking for ongoing PAH exposure might guide simple home changes like closing windows on hazy days or choosing less-charred food.
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02At a glance
03Original abstract
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants that are associated with altered neurodevelopment and various neurodevelopmental disorders. However, studies evaluating internal biomarkers of PAH exposure in reference to the severity of autism spectrum disorder (ASD) symptomology and autistic behaviors are scarce. Hence, we conducted a case-control study evaluating 12 urinary hydroxylated PAH metabolites (i.e., hydroxy-PAHs) in 101 children with autism and 101 neurotypical children, matching according to sex and age in a 1:1 ratio. In children with ASD, the severity of symptomology and autistic behaviors were assessed using the child autism rating scale (CARS) and the autism behavior checklist (ABC). We found that urinary levels of nine of the hydroxy-PAHs were statistically significantly higher in the ASD group, with the exception of 2-hydroxynaphthalene (2-OHNap) and 4-hydroxyphenanthrene (4-OHPhe). Moreover, urinary hydroxy-PAH levels were associated with ASD risk, with odds ratios ranging from 1.86 to 17.19. Exposures to 1-hydroxynaphthalene (1-OHNap, β = 3.32), hydroxyphenanthrenes (1/2/3 + 9-OHPhes, β = 3.41-5.12), 1-hydroxypyrene (1-OH-Pyr; β = 3.91), 2-hydroxybenzofuran (2-OHDBF; β = 3.93), and ∑OH-PAHs (β = 4.67) were positively associated with CARS scores after adjusting for covariates (all p < 0.05). When applying the ABC scale, 1-OHPyr levels were positively associated with ABC total scores (β = 18.54), with the strongest associations evidenced in regard to the social relatedness (β = 6.51) and language domains (β = 6.51) (all p < 0.05). Bayesian kernel machine regression (BKMR) showed consistent positive exposure responses for 1-OHNap, 1-OHPhe, and 3 + 9-OHPhe levels in regard to CARS scores, and for 1-OHPyr levels in regard to ABC total scores. Our findings suggest that children with ASD may have higher urinary levels of hydroxy-PAHs, and that these biomarker levels are associated with an increased odds of ASD, an increased severity of autism symptomology, and increased autistic behaviors in children with autism. LAY SUMMARY: We conducted an epidemiologic study evaluating the associations of urinary hydroxy-PAH levels with autism spectrum disorder (ASD), autism symptomology, and autistic behaviors. We found that urinary hydroxy-PAHs were statistically significantly associated with ASD. We note strong statistically significant associations between 1-OHNap, 1-OHPhe, and 3 + 9-OHPhe levels and increased severity of autism symptomology, as well as a strong statistically significant association between 1-OHPyr levels and behavioral characteristics within the social and linguistic domains. This work, if confirmed, will contribute to the future development of diagnostics for children with mild autism, as well as to environmental measures to promote the health and wellbeing of children with autism spectrum disorders.
Autism research : official journal of the International Society for Autism Research, 2022 · doi:10.1002/aur.2788