Prenatal methylmercury exposure is associated with neuropsychological deficits in Faroese children at age 7 years. Lower confidence bounds of benchmark doses (BMDLs) have now been calculated. With the cord-blood mercury concentration as the dose parameter, a logarithmic dose-response model tended to show a better fit than a linear dose model for the attention, language and verbal memory tests. The lowest BMDLs averaged approximately 5 microgram/l cord blood, which corresponds to a maternal hair concentration of approximately 1 microgram/g. However, most BMDLs for hair mercury concentrations were higher. Thus, the results of the benchmark calculations depend on the assumed dose-response model.
BACKGROUND: Marine food provides essential fatty acids that are important during pregnancy, but the benefits may be limited at high intakes and by seafood contaminants. METHODS: In the fishing community of the Faroe Islands, 182 pregnant women with spontaneous singleton births were consecutively recruited for a cohort in 1994- 1995. Concentrations of fatty acids and seafood contaminants in blood samples were analysed as predictors of gestational length and birthweight. RESULTS: Serum concentrations of eicosapentaenoic acid (EPA) increased with maternal marine food intake, while the tendency was less clear for docosahexaenoic acid (DHA). An increase in the relative concentration of DHA in cord serum phospholipids by 1% was associated with an increased duration of gestation by 1.5 days (95% CI : 0.7-2.2). However, birthweight adjusted for gestational length decreased by 246 g (95% CI : 16-476) for each increase by 1% of the EPA concentration in cord serum. Concentrations of the seafood pollutants mercury and polychlorinated biphenyls (PCB) were associated with fatty acids levels, but the contaminants did not appear to affect any of the outcome parameters. CONCLUSION: An increased intake of marine fats appears to prolong the duration of gestation, but birthweight adjusted for gestational age may decrease at high intake levels. This effect does not seem to be due to increased exposures to seafood contaminants.
Comment In: Int J Epidemiol. 2001 Dec;30(6):1279-8011821328
A cohort of 1,052 persons (504 men and 548 women) born in 1936 and residing in the Glostrup area, Denmark, underwent a comprehensive physical examination in 1976 at age 40 years, and 966 underwent a complete reexamination five years later. The examinations included blood lead concentration and blood pressure assessment under careful quality control. Complete blood lead and blood pressure data were available for 861 of these subjects (451 men and 410 women). The median blood lead levels were 13 and 9 micrograms/100 ml at age 40 years and 9 and 6 micrograms/100 ml at age 45 years in men and women, respectively. A slightly increased blood lead concentration was seen at age 40 years in women with a systolic blood pressure above 140 mmHg and/or a diastolic blood pressure above 90 mmHg. Systolic blood pressure in men and women and diastolic blood pressure in women correlated significantly with log blood lead at age 40 years but not at age 45 years, a doubling in blood lead being associated with an increase in blood pressure of 3 mmHg or less. Of nine potential confounders assessed, only blood hemoglobin and alleged alcohol intake were significantly associated with both blood lead and blood pressure. If one or both confounders were entered into a multiple regression analysis, all associations between blood lead and blood pressure became nonsignificant, in some cases with a negative regression coefficient. In addition, the blood lead:hemoglobin ratio was poorly associated with blood pressure, particularly in individuals with a low alcohol intake. Because both hemoglobin level and alcohol intake appear to be biologically plausible confounders, any independent effect of low-level lead exposure on blood pressure could not be determined.
Comment In: Am J Epidemiol. 1990 Jun;131(6):10982343863
Blood lead concentrations in a Danish reference population were related to information from an extensive questionnaire on work, environment and life style. The mean concentration of lead in blood was 0.167 mumol/L, i.e. significantly lower than in previous studies. This finding is in accordance with the fact that less than 10% of petrol used in Denmark contained lead additives (up to 0.15 g/L). An important finding was that the well-documented predictors for lead in blood at higher concentration levels, such as age, gender, menopausal status, and intake of alcohol, are still valid in a low-level exposure situation. In addition, a strong and negative correlation was found between blood lead concentrations and dietary supplementation with vitamins and minerals. The present data indicate that lead exposure may still constitute a health risk in a small proportion of adult males and postmenopausal women.
To explore possible markers of developmental immunotoxicity, we prospectively examined 56 children to determine associations between exposures to methylmercury and persistent organic pollutants since birth and the comprehensive differential counts of white blood cells (WBC) at age 5 years.
Extended differential count included: neutrophils, eosinophils, basophils, lymphocytes (includingT cells, NK cells, and B cells), and monocytes. Organochlorine compounds (OCs) including polychlorinated biphenyls (PCBs) and pesticides, five perfluoroalkyl substances (PFASs), and total mercury (Hg) were measured in maternal (n=56) and children's blood at 18 months (n=42) and 5 years (n=54). We constructed latent functions for exposures at three different ages using factor analyses and applied structural equation models adjusted for covariates.
Prenatal mercury exposure was associated with depleted total WBC, especially for lymphocytes, where a one standard deviation (SD) increase in the exposure was associated with a decrease by 23% SD (95% CI: -43, -4) in the cell count. Prenatal exposure to OCs was marginally associated with decreases in neutrophil counts. In contrast, the 5-year PFASs concentrations were associated with higher basophil counts (B=46% SD, 95% CI: 13, 79). Significantly reduced subpopulations of lymphocytes such as B cells, CD4-positive T helper cells and CD4 positive recent thymic emigrants may suggest cellular immunity effects and dysregulation of T-cell mediated immunity.
Developmental exposure to environmental immunotoxicants appears to have different impacts on WBC counts in childhood.
Cites: Environ Health Perspect. 2012 Apr;120(4):595-600 PMID 22275729
A cohort of 1022 consecutive singleton births was generated during 1986-1987 in the Faroe Islands. Increased methylmercury exposure from maternal consumption of pilot whale meat was indicated by mercury concentrations in cord blood and maternal hair. At approximately 7 years of age, 917 of the children underwent detailed neurobehavioral examination. Neuropsychological tests included Finger Tapping; Hand-Eye Coordination; reaction time on a Continuous Performance Test; Wechsler Intelligence Scale for Children-Revised Digit Spans, Similarities, and Block Designs; Bender Visual Motor Gestalt Test; Boston Naming Test; and California Verbal Learning Test (Children). Clinical examination and neurophysiological testing did not reveal any clear-cut mercury-related abnormalities. However, mercury-related neuropsychological dysfunctions were most pronounced in the domains of language, attention, and memory, and to a lesser extent in visuospatial and motor functions. These associations remained after adjustment for covariates and after exclusion of children with maternal hair mercury concentrations above 10 microgram(s) (50 nmol/g). The effects on brain function associated with prenatal methylmercury exposure therefore appear widespread, and early dysfunction is detectable at exposure levels currently considered safe.
Within a cohort of 1022 consecutive singleton births in the Faroe Islands, we assessed prenatal methylmercury exposure from the maternal hair mercury concentration. At approximately 7 years of age, 917 of the children underwent detailed neurobehavioral examination. Little risk is thought to occur as long as the hair mercury concentration in pregnant women is kept below 10-20 microg/g (50-100 nmol/l). A case group of 112 children whose mothers had a hair mercury concentration of 10-20 microg/g was therefore matched to children with exposure below 3 microg/g, using age, sex, time of examination, and the mother's score on Raven's Progressive Matrices as matching criteria. The two groups were almost identical with regard to other factors that might affect neurobehavioral performance in this community. On six neuropsychological test measures, the case group showed mild decrements, relative to controls, especially in the domains of motor function, language, and memory. Subtle effects on brain function therefore seem to be detectable at prenatal methylmercury exposure levels currently considered to be safe.
The purpose of the study was to examine the feasibility of a computer-assisted neuro-psychological test program, the Neurobehavioral Evaluation System (NES), in six to seven year-old children. We administered three NES tests, Finger Tapping (FT), Continuous Performance Test (CPT) and Hand-Eye Coordination (HEC) to Faroese and Danish children. The FT and CPT were of appropriate difficulty, while the HE was too difficult for the majority of the children. Boys obtained better scores than the girls, and children who were familiar with computers and video games performed better than those without such experience. Older children also obtained better scores than younger ones, especially in the Faroese group. The Danish children performed better than the Faroese in FT and CPT. In HE there was no difference. The NES tests are feasible for children at this age, but appropriate comparison groups must be secured.
A cohort of children who attended first grade in 1983 was identified in a Danish community with low-level lead pollution. Two groups with high and low postnatal lead exposure were generated on the basis of the dentin-lead concentration in shed deciduous incisors. At age 8 years, examination of 162 children matched according to gender and socioeconomic status had shown lead-related deficits in verbal intelligence and visuomotor coordination. Re-examination was now carried out in 141 children at age 15 years using the Wechsler Intelligence Scale for Children (WISC), Bender Visual Motor Gestalt, Trail Making, and Visual Gestalts. In general, no lead-related effects could be detected in the group. However, in children with a history of neonatal jaundice, increased lead exposure was associated with mild neurobehavioral deficits, as indicated by lower verbal IQ scores and decreased visuomotor coordination. This finding suggested that moderate neonatal hyperbilirubinemia may have precipitated an increased sensitivity to subsequent exposure to lead.