Early-life DL-PCB exposure is associated with telomere shortening and impaired higher-order cognitive function, with leukocyte telomere length acting as a partial mediator explaining approximately 5-10% of the total effect.
Key Findings
Results
Serum concentrations of PCB77, PCB126, and PCB189 were significantly associated with shorter leukocyte telomere length (LTL) after Bonferroni correction.
Study population consisted of 1756 primary school children aged 7-10 years from Shenyang, China.
PCB189 showed the strongest individual association: β = -0.041 per IQR increase, adjusted p = 0.001.
LTL was quantified via qRT-PCR.
Twelve DL-PCB congeners were measured in serum.
Associations survived Bonferroni correction for multiple comparisons.
Results
DL-PCB mixtures were strongly associated with shorter leukocyte telomere length across multiple mixture analysis methods.
Generalized Weighted Quantile Sum regression (gWQS) yielded β = -0.055, p < 0.001.
Bayesian Kernel Machine Regression (BKMR) was also applied and confirmed the association.
Consistency across three distinct mixture analysis approaches strengthens the robustness of the finding.
Results
PCB81 and PCB189 showed robust negative associations with superior working memory as measured by the Three-Back task.
Associations with the Three-Back task remained significant after adjustment (adjusted p < 0.05).
Basic working memory assessed by the Two-Back task exhibited no significant associations with any DL-PCB congener.
This suggests DL-PCB exposure specifically impairs higher-order cognitive function rather than basic working memory.
Mixture analyses also confirmed that DL-PCB mixtures were associated with poorer superior working memory.
Results
Inattentiveness (measured by HRT-SE) was negatively associated with several DL-PCB congeners in crude models, but associations were attenuated after multiple-testing correction.
PCB157, PCB167, PCB169, and PCB189 were negatively associated with HRT-SE (a measure of inattentiveness) in crude models.
These associations did not survive correction for multiple comparisons.
Mixture analyses confirmed that DL-PCB mixtures were associated with poorer inattentiveness outcomes.
Cognitive outcomes were assessed using the Attentional Network Test (ANT) for attention measures.
Results
Leukocyte telomere length mediated approximately 5-10% of the total effect of specific DL-PCB congeners on superior working memory and inattentiveness.
Mediation analysis identified LTL as a partial mediator for the effects of PCB77, PCB81, PCB169, and PCB189.
LTL explained approximately 5-10% of the total effect on superior working memory and inattentiveness.
The mediation was partial, indicating other pathways also contribute to DL-PCB-associated cognitive deficits.
Linear mixed models were used for individual congener analyses, adjusting for relevant covariates.
Background
The study hypothesized and tested a mechanistic pathway whereby DL-PCB-induced oxidative stress and inflammation accelerate telomere shortening, which in turn impairs neurodevelopment.
DL-PCBs are described as persistent environmental pollutants known to induce oxidative stress and inflammation.
The study design measured serum DL-PCB levels, LTL, and cognitive performance simultaneously in the same children.
Analytical approaches included linear mixed models, three mixture analyses (g-comp, gWQS, BKMR), and mediation analysis.
What This Means
This research studied whether exposure to a class of industrial chemicals called dioxin-like polychlorinated biphenyls (DL-PCBs) — persistent pollutants found in the environment and food chain — is linked to shorter telomeres and worse cognitive performance in children. Telomeres are protective caps on chromosomes that shorten with age and stress; shorter telomeres are generally associated with poorer cellular health. The study examined 1,756 primary school children aged 7-10 in Shenyang, China, measuring the children's blood levels of 12 different DL-PCB chemicals, the length of their telomeres in white blood cells, and their performance on standardized cognitive tests measuring working memory and attention.
The study found that higher exposure to several specific DL-PCBs — particularly PCB77, PCB126, and PCB189 — was associated with shorter telomeres. Higher DL-PCB levels were also associated with worse performance on a demanding working memory task (the Three-Back test, which requires tracking information three steps back in sequence), though not on a simpler version of the task. Importantly, telomere shortening appeared to partially explain the link between DL-PCB exposure and worse cognitive performance, accounting for roughly 5-10% of the effect. This suggests that telomere damage may be one biological mechanism through which these chemicals affect children's brain development, though other mechanisms are also likely involved.
This research suggests that early-life exposure to DL-PCBs — chemicals that accumulate in the environment and can enter the body through food and other sources — may harm children's developing cognitive abilities in part by accelerating the biological aging of their cells. The finding that higher-order cognitive functions (like complex working memory) appear more vulnerable than basic cognitive functions highlights a potential concern for children's academic and developmental outcomes in areas with elevated environmental PCB contamination. The results add to growing evidence linking environmental pollutant exposure to measurable biological changes and cognitive outcomes in children.
Liu L, Wang J, Chang H, Hu Y, Zhang H, Wei H, et al.. (2026). Mediating role of telomere shortening in dioxin-like polychlorinated biphenyls associated cognitive decline in children.. Environmental health : a global access science source. https://doi.org/10.1186/s12940-026-01319-2