Assessment of bone lead during pregnancy: a pilot study

Lead Absorption and Excretion in Rats Given Insoluble Salts of Pectin and Alginate

Exposure to environmental lead remains a widespread problem in most industrialized countries. Usage of modern agents purposed for elimination of heavy metals as well as for therapy and prevention of chronic poisoning does frequently result in toxic signs. Dietary nonstarch polysaccharides were suggested to be effective when used for this purpose. The present study was conducted to estimate metal binding capacity and effects of calcium salts of pectate and alginate on lead absorption, distribution, and removal with feces. Under in vitro conditions calcium alginate showed the highest lead-binding capacity in comparison with other agents studied. Metal binding capacity of calcium pectate was slightly lower. In rats simultaneous administration of lead acetate and suspensions containing calcium alginate or calcium pectate prevented metal absorption and significantly reduced lead accumulation in inner organs and femur. In experiments estimating lead removal from inner organs and femur in rats preliminary exposed to the heavy metal, calcium alginate and calcium pectate were the most effective agents studied in comparison with others, as indicated by reduced lead concentration in organs and femur as well as increased metal content in feces of laboratory animals. The results suggest that calcium pectate and calcium alginate may be considered perspective dietary compounds purposed for prevention and treatment of chronic lead poisoning.

Association of blood lead levels with methylenetetrahydrofolate reductase polymorphisms among Chinese pregnant women in Wuhan city

BACKGROUND

Pregnancy is an important stimulus of bone lead release. Elevated blood lead levels (BLLs) may cause adverse pregnancy outcomes for mothers and harmful lead effects on fetuses. However, the reports about maternal BLL changes during pregnancy are conflicting to some extent. This article is to explore the variations in BLLs among pregnant women. The relationships of BLLs with methylenetetrahydrofolate reductase (MTHFR) gene C677T, A1298C, and G1793A polymorphisms, which are associated with bone resorption, were also studied. A total of 973 women, including 234, 249, and 248 women in their first, second, and third trimesters, respectively, and 242 non-pregnant women, were recruited at the Wuhan Women and Children Medical Health Center.

METHODS

BLLs were determined using a graphite furnace atomic absorption spectrometer. Single-nucleotide polymorphisms of MTHFR were identified with the TaqMan probe method.

RESULTS

The geometric mean (geometric standard deviation) of BLLs was 16.2 (1.78) μg/L for all participants. All the studied MTHFR alleles were in Hardy-Weinberg equilibrium. Multiple-linear regression analysis revealed the following results. Among the pregnant women, those that carried MTHFR 677CC (i.e. wild-genotype homozygote) and 1298CC (i.e. mutant-genotype homozygote) exhibited higher BLLs than those that carried 677CT/TT (standardized β = 0.074, P = 0.042) and 1298AC/AA (standardized β = 0.077, P = 0.035) when other covariates (e.g., age, no. of children, education and income, etc.) were adjusted. The BLLs of pregnant women consistently decreased during the pregnancy and these levels positively correlated with BMI (standard β = 0.086-0.096, P<0.05).

CONCLUSIONS

The 1298CC mutant-type homozygote in the MTHFR gene is a risk factor for high BLLs among low-level environmental lead-exposed Chinese pregnant women, whose BLLs consistently decreased during gestation.

An unexplained case of elevated blood lead in a Hispanic child

A 6-month-old child presented to a local pediatrician with an elevated blood lead level (BLL) of 41 microg/dL. The child was treated as an outpatient for chelation therapy by a toxicologist. Subsequent BLLs obtained at 8 and 13 months of age were 40 microg/dL and 42 microg/dL, respectively. Siblings and family members had BLLs < 5 microg/dL except for the mother, who had a BLL of 14 microg/dL when the child was 6 months of age. Home inspections and phone calls to the family revealed no sources of lead from paint, dust, toys, mini-blinds, keys, food, water, or any take-home exposure. The family denied use of folk remedies such as Greta and Azarcon. The child was breast-fed, but the mother's BLL was not sufficiently high to explain the elevated BLL in the child. Housekeeping was excellent. The mother did admit to cooking beans in Mexican pottery (pieces found outside were positive for lead), but she discontinued use after the initial lead check at 6 months. The bean pot was not a likely source, as none of the family had elevated BLLs including a 5-year-old sister. Follow-up testing of blood lead when the child was 15 months of age revealed values of 28 microg/dL for the child and 9 microg/dL for the mother. Subsequent testing of the child shows a slow decline. The slow release of lead suggests depletion of bone stores acquired during pregnancy, possibly due to pica behavior of the mother during pregnancy.

A randomized trial of calcium supplementation for childhood lead poisoning

OBJECTIVE

Lead (Pb) poisoning remains a common disease among children despite successful public health efforts that have reduced its prevalence. Treatment options for children with blood Pb levels (BPbs) <45 micro g/dL are limited because chelation therapy is generally not indicated. Calcium (Ca) and Pb interactions are well documented. Competition for binding to Ca-binding proteins may underlie a mechanism for Pb absorption. The purpose of this study was to determine the role, if any, of supplemental Ca at reducing BPbs in moderately poisoned children.

METHODS

Children aged 1 to 6 years with BPbs 10 to 45 micro g/dL were enrolled in a double-blinded, placebo-controlled trial of the effects of Ca supplementation on BPbs. Children received either a Ca-containing liquid or an indistinguishable placebo. Dosage was adjusted biweekly on the basis of responses to a dietary Ca intake questionnaire to reach 1800 mg in the Ca-supplemented group. Samples for BPbs and measures to assess safety were collected before and after 3 months of supplementation and after an additional 3 months of follow-up. Bivariate and multiple regression analyses were performed.

RESULTS

A total of 67 of 88 enrolled children with a mean age of 3.6 years completed 3 months of supplementation. There were no statistically significant differences between groups on hematologic and biochemical measures, including serum and urinary Ca, at any time points. The average compliance rate was estimated to be 80% for each group during the 3-month supplementation period.

CONCLUSIONS

At enrollment, the average daily Ca intake in this group of inner-city children was greater than the recommended daily intake for age. Although BPbs declined during a 3-month period in both groups, Ca supplementation aimed at providing 1800 mg of Ca/day had no effect on the change in BPbs. Ca supplementation should not be routinely prescribed for mild to moderately Pb-poisoned children who are dietarily Ca sufficient.

Should the Centers for Disease Control and Prevention's childhood lead poisoning intervention level be lowered?

The US Centers for Disease Control and Prevention (CDC) in 1991 chose 10 micro g/dL as an initial screening level for lead in children's blood. Current data on health risks and intervention options do not support generally lowering that level, but federal lead poisoning prevention efforts can be improved by revising the follow-up testing schedule for infants aged 1 year or less with blood lead levels of 5 micro g/dL or higher; universal education about lead exposure risks; universal administration of improved, locally validated risk-screening questionnaires; enhanced compliance with targeted screening recommendations and federal health program requirements; and development by regulatory agencies of primary prevention criteria that do not use the CDC's intervention level as a target "safe" lead exposure.

Lead poisoning in pregnancy: a case study with implications for midwives

Lead poisoning remains a significant problem in the United States affecting the health of women and children. Although the damage is greatest at higher levels of accumulation, no level of lead has been found to be safe. Over the last 25 years, the blood level of lead thought to be associated with toxicity has dropped dramatically, from to 60 mcg/dL in 1960 to 10 mcg/dL today. Studies confirm that exposure to lead causes kidney damage, encephalopathy, and impaired cognitive function in children and in adults. Recent evidence indicates children with levels less than 10 mcg/dL may suffer from compromised development and intellectual performance later in life. This article discusses the case of a woman found to have lead poisoning during pregnancy. Environmental sources of lead, implications for the immediate and future health of the fetus and mother, and techniques clinicians can use in their practice to minimize the adverse effect of lead on their clients are reviewed.

Effect of maternal bone lead on length and head circumference of newborns and 1-month-old infants

The authors evaluated the effects that maternal bone lead stores have in anthropometry at birth in 223 mother-infant pairs. The participants were recruited between April and November 1994. Anthropometric data were collected within the first 12 hr following delivery. Maternal information was obtained 1 mo after delivery occurred. Bone lead burden was determined with in-vivo K-x-ray fluorescence of the tibia (cortical bone) and the patella (trabecular bone). The authors transformed anthropometric measurements to an ordinal 5-category scale, and the association of measurements with other factors was evaluated with ordinal logistic-regression models. Mean bone lead levels were 9.8 microgram/gm bone mineral and 14.4 microgram/gm bone mineral for the tibia and patella, respectively. Birth length of newborns decreased as tibia lead levels increased. Compared with women in the lower quintiles of the distribution of tibia lead, those in the upper quintile had a 79% increase in risk of having a lower birth length newborn (odds ratio = 1.79; 95% confidence interval = 1.10, 3.22). The authors adjusted by birth weight, and the effect was attenuated--but nonetheless significant. Patella lead was positively and significantly related to the risk of a low head circumference score; this score remained unaffected by inclusion of birth weight. The authors estimated the increased risk to be 1.02 per microgram lead/gm bone mineral (95% confidence interval = 1.01, 1.04 per microgram lead/gm bone mineral). Odds ratios did not vary substantially after the authors adjusted for birth weight and other important determinants of head circumference.