Lead, cadmium and mercury levels in pregnancy: the need for international consensus on levels of concern

Abstract

For heavy metals that have any degree of transfer though the placenta to the fetus, it is unlikely that there are safe limits for maternal blood levels. The only means of reducing fetal exposure is to minimise maternal exposure. There are few recommendations for levels of concern. With the exception of US recommendations for maternal Pb levels, but there are no international levels of concern or cut-off levels specifically for pregnancy for heavy metals, so that comparisons can generally only be made with national reference values relating to similar physiological statuses or age groups. These include recommendations for Cd levels by Germany (reference value for non-smoking adults aged 18-69 years, 1 µg/l) and for Hg by Germany (reference value for adults age 18-60 years with fish intake < or =3 times per month, 2.0 µg/l) and the USA (cut-off level for women, 5.8 µg/dl). To illustrate the lack of cohesion, we present data on blood Pb, Cd and Hg levels from pregnant women enroled in the UK Avon Longitudinal Study of Parents and Children study and compare the values with present levels of concern and recommended cut-off values. We also compare the levels with those found in other groups of pregnant women worldwide to strengthen the database for the development of levels of concern in pregnancy. The need for clarity of terminology in describing levels of concern is discussed. There is a pressing need for international consensus on levels of concern for all age groups and physiological statuses, particularly for pregnancy.

Moderate Prenatal Cadmium Exposure and Adverse Birth Outcomes: a Role for Sex‐Specific Differences?

“…As reported previously, the mean B‐Cd level was similar to those reported in other developed countries 25. The mean B‐Cd level in smokers was 77% greater than in non‐smokers and increased with the number of cigarettes smoked (Table S3).…”

Perinatal and Childhood Exposure to Cadmium, Manganese, and Metal Mixtures and Effects on Cognition and Behavior: A Review of Recent Literature

“…Anthropogenic sources of Cd also include industrial smelters, phosphate fertilizers, and nickel-cadmium batteries [19]. Although the placenta protects the fetus by restricting Cd, Cd levels can be detectable in newborn cord blood despite the limited transfer at the maternal-fetal interface [20–22]. Postnatal Cd exposure can also occur through secondhand tobacco smoke, infant formula [23, 24] or breast milk [25], and the primary source of Cd in childhood is dietary.…”

The Effects of Diet and the Microbiome on Reproduction and Longevity: A Comparative Review Across 5 Continents

“…Given the importance of the former in neural development [83] and the latter in potentially countering bacterial vaginosis and preterm birth [84], further studies are merited. The lactobacilli may also be beneficial to counter environmental toxins [85], which some naturopaths encourage avoidance of by consuming of fresh, organically grown food [86]. Toxins, such as mercury and organochlorine pesticides, are known to adversely affect pregnancy and infant outcomes including birth size, reflexes, attention, alertness and performance impairment [87][88][89][90][91].…”