Effect of food intake on blood lead concentration in workers occupationally exposed to lead

Chelation: harnessing and enhancing heavy metal detoxification--a review

Toxic metals such as arsenic, cadmium, lead, and mercury are ubiquitous, have no beneficial role in human homeostasis, and contribute to noncommunicable chronic diseases. While novel drug targets for chronic disease are eagerly sought, potentially helpful agents that aid in detoxification of toxic elements, chelators, have largely been restricted to overt acute poisoning. Chelation, that is multiple coordination bonds between organic molecules and metals, is very common in the body and at the heart of enzymes with a metal cofactor such as copper or zinc. Peptides glutathione and metallothionein chelate both essential and toxic elements as they are sequestered, transported, and excreted. Enhancing natural chelation detoxification pathways, as well as use of pharmaceutical chelators against heavy metals are reviewed. Historical adverse outcomes with chelators, lessons learned in the art of using them, and successes using chelation to ameliorate renal, cardiovascular, and neurological conditions highlight the need for renewed attention to simple, safe, inexpensive interventions that offer potential to stem the tide of debilitating, expensive chronic disease.

Determinants of the blood lead level of US women of reproductive age

OBJECTIVES

Blood lead concentration of an infant is largely affected by maternal blood lead recycling. This study aimed to identify sociodemographic, lifestyle, and nutritional determinants for blood lead levels (BLLs) of women of reproductive age in the United States.

METHODS

Subjects (n = 4,394) were women (20-49 years old) included in the most recent complete National Health and Nutritional Survey (NHANES III). Certain sociodemographic, lifestyle and nutritional determinants for BLL were identified.

RESULTS

The BLL of reproductive age women was 1.78 microg/dL geometric mean, The BLL was inversely associated with poverty income ratio and education level, hematocrit, intake of thiamine, and serum levels of folate, and positively associated with ethnicity (Black, Hispanic), living in urban areas or the Northeast region, age, alcohol consumption, cigarette smoking, serum protoporphyrin, and intake of pyridoxine, iron, and folate. Subjects in the lowest decile for serum ascorbic acid had significantly higher BLLs than those in the 2nd through 8th deciles.

CONCLUSION

Infants born to women who smoke, drink and maintain poor nutritional status for selected nutrients are at a greater risk of lead toxicity than those born to other women. Nutritional manipulation of thiamine, ascorbic acid and folate may impact BLL in women.

Toxic interactions among environmental pollutants: corroborating laboratory observations with human experience

Combined exposures to multiple chemicals may result in interactions leading to a significant increase or decrease in the overall toxicity of the mixture compared to the summation of the toxicity of the components. A large number of chemical interactions have been described in animal studies by administering high doses of chemicals by routes and scenarios often different from anticipated human exposures. Though limited, there is some evidence for the occurrence of several supra-additive (the combined effects are greater than the simple summation of the individual effects) and infra-additive (the combined effects are smaller than the simple summation of the individual effects) chemical interactions in humans. For example, toxicokinetic interactions between several solvents have been found to occur in the workplace, whereas those involving pesticides have been reported less frequently, especially during accidental exposures. Toxic interactions involving nutritionally important metals and metalloids appear to occur more frequently, since several of them have an important role in a variety of physiological and biochemical processes. On the contrary, there is not much evidence to confirm the occurrence of toxic interactions among the commonly encountered inorganic gaseous pollutants in humans. Overall, the majority of chemical interactions observed in animal studies have neither been investigated in humans nor been extrapolated to humans based on appropriate mechanistic considerations. Future research efforts in the chemical interactions arena should address these issues by focusing on the development of mechanistically and biologically based models that allow predictions of the extent of interactions likely to be observed in humans.

Temporal changes in blood lead levels of hazardous waste workers in New Jersey, 1984-1987

The blood lead levels of 568 New Jersey hazardous waste workers were determined at least once in the period 1984-1987. Workers almost always wore protective clothing in the field, which should have prevented exposure to lead. Therefore, despite their occupation, these workers are probably representative of the New Jersey suburban population in the mid-1980s. Blood lead levels ranged from 2.0-20.7 µg/dL, with an arithmetic mean value of 5.8 µg/dL, representing a decline from levels measured a decade earlier, but there was no clear change over the four years of the study. Blood lead levels increased with age of the worker up to age 60. Women showed lower levels than men in every age group.

The effects of thiamin on the tissue distribution of lead

The effects of thiamin on the tissue distribution of lead were evaluated in Sprague-Dawley rats exposed to 1000 ppm lead acetate in drinking water and treated daily with thiamin (25 or 50 mg kg-1 body weight, i.p.), calcium ethylenediamine tetraacetic acid (50 mg kg-1 body weight, i.p.) or their combination for 8 weeks. The subtoxic dose of lead did not alter weight gains, feed and water consumption during the treatment period. Thiamin decreased the blood (P less than 0.0001), liver (P less than 0.0001) and kidney (P less than 0.0001) concentrations of lead. Thiamin (50 mg kg-1 body weight) reduced the lead concentrations in tissues more effectively than thiamin (25 mg kg-1 body weight). The combined treatment was more effective than the respective individual treatments.

Effect of thiamine on the excretion of subcutaneously injected lead in rats

The effect of thiamine on the excretion of lead in feces was investigated using rats injected subcutaneously with lead acetate and thiamine pyrophosphate. The amount of lead excreted increased with the amounts of thiamine administered, while lead concentrations in blood, liver and femur also increased. The amount of lead excreted in feces decreased, however, with administration of oxythiamine and vanadium. These results suggest that excretion of lead in feces is enhanced by thiamine and that it promotes evacuation of lead from the body.