Dataset Information

Prenatal mercury exposure and features of autism: a prospective population study.

ABSTRACT:

Background

Mercury (Hg) has been suspected of causing autism in the past, especially a suspected link with vaccinations containing thiomersal, but a review of the literature shows that has been largely repudiated. Of more significant burden is the total quantity of Hg in the environment. Here, we have used the Avon Longitudinal Study of Parents and Children (ALSPAC) to test whether prenatal exposure from total maternal blood Hg in the first half of pregnancy is associated with the risk of autism or of extreme levels of autistic traits. This is the largest longitudinal study to date to have tested this hypothesis and the only one to have considered early pregnancy.

Methods

We have used three strategies: (1) direct comparison of 45 pregnancies resulting in children with diagnosed autism from a population of 3840, (2) comparison of high scores on each of the four autistic traits within the population at risk (n~2800), and (3) indirect measures of association of these outcomes with proxies for increased Hg levels such as frequency of fish consumption and exposure to dental amalgam (n?>?8000). Logistic regression adjusted for social conditions including maternal age, housing circumstances, maternal education, and parity. Interactions were tested between risks to offspring of fish and non-fish eaters.

Results

There was no suggestion of an adverse effect of total prenatal blood Hg levels on diagnosed autism (AOR 0.89; 95% CI 0.65, 1.22) per SD of Hg (P?=?0.485). The only indication of adverse effects concerned a measure of poor social cognition when the mother ate no fish, where the AOR was 1.63 [95% CI 1.02, 2.62] per SD of Hg (P?=?0.041), significantly different from the association among the offspring of fish-eaters (AOR?=?0.74 [95% CI 0.41, 1.35]).

Conclusion

In conclusion, our study identifies no adverse effect of prenatal total blood Hg on autism or autistic traits provided the mother ate fish. Although these results should be confirmed in other populations, accumulating evidence substantiates the recommendation to eat fish during pregnancy.

SUBMITTER: Golding J

PROVIDER: S-EPMC5914043 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Publications

Prenatal mercury exposure and features of autism: a prospective population study.

Golding Jean J Rai Dheeraj D Gregory Steven S Ellis Genette G Emond Alan A Iles-Caven Yasmin Y Hibbeln Joseph J Taylor Caroline C

Molecular autism 20180423

<h4>Background</h4>Mercury (Hg) has been suspected of causing autism in the past, especially a suspected link with vaccinations containing thiomersal, but a review of the literature shows that has been largely repudiated. Of more significant burden is the total quantity of Hg in the environment. Here, we have used the Avon Longitudinal Study of Parents and Children (ALSPAC) to test whether prenatal exposure from total maternal blood Hg in the first half of pregnancy is associated with the risk o ...[more]

PMID: 29713443

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Project description:Study questionIs in utero exposure to mercury associated with the risk of precocious puberty?Summary answerPrenatal exposure to high levels of mercury was associated with increased risk of precocious puberty, which was strengthened by concomitant maternal cardiometabolic conditions and adverse birth outcomes.What is known alreadyThe developing fetus is sensitive to mercury, a well-known endocrine disruptor which impacts the endocrine and reproductive system.Study design, size, durationThis study included 1512 mother-child pairs from the Boston Birth Cohort, a longitudinal cohort which recruited at birth and followed prospectively up to 21 years of age.Participants/materials, setting, methodsMother-child pairs, from a predominantly urban minority population, were enrolled from 2002 to 2013. Prenatal exposure was assessed by maternal mercury concentration in red blood cells (RBCs) collected at 1-3 days after delivery. Precocious puberty was defined based on International Classification of Disease codes. Cox proportional hazards models were applied to the association between maternal mercury concentrations and the risk of precocious puberty.Main results and the role of chanceThe median (interquartile range) of maternal mercury concentrations among children with and without precocious puberty were 3.4 (1.9-4.6) µg/l and 2.0 (1.0-3.7) µg/l, respectively. Compared to those in the lowest tertile for mercury, the highest tertile was associated with increased risk of precocious puberty, with an adjusted hazard ratio (HR) of 2.41, 95% CI: 1.16-5.03. In addition, concomitant maternal cardiometabolic conditions and adverse birth outcomes strengthened the effects of mercury on the risk of precocious puberty. The highest risk of precocious puberty was observed among children who had adverse birth outcomes and whose mothers had high RBC-mercury concentrations along with cardiometabolic conditions, with an HR of 4.76 (95% CI: 1.66-13.60) compared to children with favorable profiles of all three risk factors.Limitations, reasons for cautionPrecocious puberty was defined based on medical records, not on a direct assessment, which may have led to underdiagnosis and the inability to make a subclassification. The study included a predominately urban, low-income, minority population and as such our findings may not be widely generalizable.Wider implications of the findingsPrenatal Hg exposure was associated with an increased risk of precocious puberty. This risk was strengthened by concomitant maternal cardiometabolic conditions during pregnancy and adverse birth outcomes.Study funding/competing interest(s)This study was funded by the NIH/National Institute of Environmental Health Sciences, NIH/Eunice Kennedy Shriver National Institute of Child Health and Human Development and the Health Resources and Services Administration of the U.S. Department of Health and Human Services. The authors declare no conflicts of interest.Trial registration numberN/A.

Project description:ObjectiveTo examine associations between early developmental exposure to ambient pesticides and autism spectrum disorder.DesignPopulation based case-control study.SettingCalifornia's main agricultural region, Central Valley, using 1998-2010 birth data from the Office of Vital Statistics.Population2961 individuals with a diagnosis of autism spectrum disorder based on the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, revised (up to 31 December 2013), including 445 with intellectual disability comorbidity, were identified through records maintained at the California Department of Developmental Services and linked to their birth records. Controls derived from birth records were matched to cases 10:1 by sex and birth year.ExposureData from California state mandated Pesticide Use Reporting were integrated into a geographic information system tool to estimate prenatal and infant exposures to pesticides (measured as pounds of pesticides applied per acre/month within 2000 m from the maternal residence). 11 high use pesticides were selected for examination a priori according to previous evidence of neurodevelopmental toxicity in vivo or in vitro (exposure defined as ever v never for each pesticide during specific developmental periods).Main outcome measureOdds ratios and 95% confidence intervals using multivariable logistic regression were used to assess associations between pesticide exposure and autism spectrum disorder (with or without intellectual disabilities) in offspring, adjusting for confounders.ResultsRisk of autism spectrum disorder was associated with prenatal exposure to glyphosate (odds ratio 1.16, 95% confidence interval 1.06 to 1.27), chlorpyrifos (1.13, 1.05 to 1.23), diazinon (1.11, 1.01 to 1.21), malathion (1.11, 1.01 to 1.22), avermectin (1.12, 1.04 to 1.22), and permethrin (1.10, 1.01 to 1.20). For autism spectrum disorder with intellectual disability, estimated odds ratios were higher (by about 30%) for prenatal exposure to glyphosate (1.33, 1.05 to 1.69), chlorpyrifos (1.27, 1.04 to 1.56), diazinon (1.41, 1.15 to 1.73), permethrin (1.46, 1.20 to 1.78), methyl bromide (1.33, 1.07 to 1.64), and myclobutanil (1.32, 1.09 to 1.60); exposure in the first year of life increased the odds for the disorder with comorbid intellectual disability by up to 50% for some pesticide substances.ConclusionFindings suggest that an offspring's risk of autism spectrum disorder increases following prenatal exposure to ambient pesticides within 2000 m of their mother's residence during pregnancy, compared with offspring of women from the same agricultural region without such exposure. Infant exposure could further increase risks for autism spectrum disorder with comorbid intellectual disability.

Project description:BackgroundThere is considerable discussion over the possible harm caused by fetal exposure to mercury, but evidence of such harm is contradictory at levels commonly found in populations with moderate intakes of fish. Further information is needed to inform debate and clarify policy recommendations.MaterialData were collected prospectively for the Avon Longitudinal Study of Parents and Children (ALSPAC). Whole blood taken in the first half of pregnancy was assayed for mercury. The outcomes were offspring behavioural assessments collected using the Strengths and Difficulties Questionnaire at seven time points between ages 4 and 16-17 years; five were completed by the mother and two by the teacher. Socioeconomic and biological confounders were first taken into account; further analyses added maternal blood selenium. Separate analyses compared the relationships between prenatal mercury levels and behaviour traits treated as continuous measures in women who ate fish with those who ate no fish in order to determine whether the relationships differed; the hypothesis was that fish consumption had benefits on the brain and masked any mercury effects. In order to prevent Type II errors, the P value for significance was set at 0.10.ResultsPrenatal mercury measurements and offspring behaviour results were available for between 2776 (at 47 months) to 1599 mother-child pairs (at 16-17 years). Even given a P value of 0.10, the number of significant results was no greater than expected apart from the relationships with peer problems at 4, 6 and 10-11 years where the relationships with prenatal mercury were negative (i.e. the greater the level of mercury the fewer the problems the child had with his/her peers). There were no significant differences between the associations with mercury found among the offspring of women who ate fish in pregnancy and those who did not, nor did adjustment for selenium make a difference.ConclusionsThere were no adverse effects of maternal prenatal mercury levels on the behaviour of the offspring. A similar lack of relationship was found when the analyses were confined to those offspring whose mothers had eaten fish in pregnancy, and no consistent differences were found between the fish and non-fish eaters.

Project description:BackgroundEvidence from experimental and observational studies suggests that prenatal phthalate exposures may be associated with autism spectrum disorder (ASD). We examined whether prenatal phthalate exposures were associated with an increased risk of ASD.MethodsWe quantified 14 metabolites of eight phthalates in 636 multiple maternal urine samples collected during 2nd and 3rd trimesters of pregnancy from 201 mother-child pairs in MARBLES (Markers of Autism Risk in Babies - Learning Early Signs), a high-risk ASD longitudinal cohort. At 3?years old, children were clinically assessed for ASD and classified into three diagnostic categories: ASD (n?=?46), non-typical development (Non-TD, n?=?55), and typical development (TD, n?=?100). We used multinomial logistic regression to evaluate the association of phthalate metabolite concentrations with ASD and Non-TD.ResultsMost associations of phthalate biomarkers with both ASD and Non-TD were null, with the exception that monoethyl phthalate (MEP) was significantly associated with an increased risk of Non-TD (per 2.72-fold relative increase in concentration: Relative risk ratio (RRR)?=?1.38; 95% confidence interval (CI): 1.01, 1.90). When stratified by prenatal vitamin use during the first month of pregnancy, among mothers who took vitamins, ASD risk was inversely associated with mono-isobutyl phthalate (MiBP, RRR?=?0.44; 95% CI: 0.21, 0.88), mono(3-carboxypropyl) phthalate (MCPP, RRR?=?0.41; 95% CI: 0.20, 0.83) and mono-carboxyisooctyl phthalate (MCOP, RRR?=?0.49; 95% CI: 0.27, 0.88), but among mothers who did not take prenatal vitamins, Non-TD risk was positively associated with MCPP (RRR?=?5.09; 95% CI: 2.05, 12.6), MCOP (RRR?=?1.86; 95% CI: 1.01, 3.39), and mono-carboxyisononyl phthalate (MCNP, RRR?=?3.67; 95% CI: 1.80, 7.48). When stratified by sex, among boys, MEP, monobenzyl phthalate, MCPP, MCNP, and sum of di(2-ethylhexyl) phthalate metabolites (?DEHP) were positively associated with Non-TD risk, but associations with ASD were null. Among girls, associations with both ASD and Non-TD were null.ConclusionsOur study showed that phthalate exposures in mid- to late pregnancy were not associated with ASD in children from this high-risk ASD cohort. Further studies should be conducted in the general population without high-risk genes to confirm our findings.

Dataset Information

Prenatal mercury exposure and features of autism: a prospective population study.

Background

Methods

Results

Conclusion

Publications

Prenatal mercury exposure and features of autism: a prospective population study.

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