Prenatal exposure to legacy contaminants and visual acuity in Canadian infants: a maternal-infant research on environmental chemicals study (MIREC-ID)
- DOI
- Language of the publication
- English
- Date
- 2020-02-07
- Type
- Article
- Author(s)
- Polevoy, C.
- Arbuckle, T.E.
- Oulhote, Y.
- Lanphear, B.P.
- Cockell, K.A.
- Muckle, G.
- Saint-Amour, D.
- Publisher
- BMC
Abstract
Background: Prenatal exposure to environmental contaminants can have deleterious effects on child development. While psychomotor, cognitive and behavioural outcomes have been investigated in relation to chronic exposure, the associations with visual functions remains unclear. The present study's aim was to assess the associations of prenatal exposure to legacy persistent organic pollutants and heavy metals with visual acuity in Canadian infants. The potential protective effects of selenium against mercury toxicity were also examined. Methods: Participants (mean corrected age = 6.6 months) were part of the Maternal-Infant Research on Environmental Chemicals (MIREC) study. Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), lead and mercury were measured in maternal blood during pregnancy, as well as in the cord blood. The Teller acuity card test (TAC) (n = 429) and the visual evoked potentials in a sub-group (n = 63) were used to estimate behavioural and electrophysiological visual acuity, respectively. Multivariable linear regression models were used to investigate the relationship between exposure to each contaminant and visual acuity measures, while controlling for potential confounders. Breastmilk selenium, which was available for about half of the TAC and VEP samples, was also taken into account in the mercury models as exploratory analyses. Results: We observed no significant associations between exposure to any contaminants and TAC. Analyses revealed a negative trend (p values < 0.1) between cord blood lead and mercury and electrophysiological visual acuity, whereas PCB and PBDE showed no association. When adding breastmilk selenium concentration to the mercury models, this association became statistically significant for cord concentrations (β = - 3.41, 95% CI = - 5.96,-0.86), but also for blood levels at 1st and 3rd trimesters of pregnancy (β = - 3.29, 95% CI = - 5.69,-0.88). However, further regression models suggested that this change in estimates might not be due to adjustment for selenium, but instead to a change in the study sample. Conclusions: Our results suggest that subtle, but detectable alterations of infant electrophysiological visual acuity can be identified in a population prenatally exposed to low mercury concentrations. Compared to behavioural visual acuity testing, electrophysiological assessment may more sensitive in detecting visual neurotoxicity in relation with prenatal exposure to mercury.
Plain language summary
"Health Canada is responsible for helping Canadians maintain and improve their health. Visual acuity (seeing small letters or numbers on an eye chart) is difficult to assess in infants. In infants, the Teller Acuity Card (TAC) is used. In this test, the infants turn their eyes towards the card when they see black and white stripes of different sizes. Another tool is the Visual Evoked Potentials (VEP) where the infant’s brain activity is recorded while black and white stripes of different sizes are presented on a computer screen. The aim of this study was to assess the association between infant visual acuity and prenatal exposure to metals or persistent organic pollutants (PCBs and polybrominated flame retardants (PBDEs)). Blood lead and mercury were measured during pregnancy and in the umbilical cord blood in the MIREC Study. PCBs and PBDEs were measured in 1st trimester maternal bloods. In 6-month old infants, visual acuity was measured using the TAC (n=429) and VEP (n=63 infants). No associations were found between any of the chemicals and visual acuity as measured by the TAC. However, higher levels of mercury in maternal or cord blood were associated with lower visual acuity when measured using VEP and controlling for selenium levels in breastmilk. Selenium is an essential mineral. These results suggest that small changes in infant VEP can be measured following prenatal exposure to mercury, especially when selenium levels are considered. This study was led by scientists at the University of Montreal and Health Canada."
Subject
- Health,
- Health and safety