Stable Isotopic Tracing—A Way Forward for Nanotechnology

Numerous publications and reports have expressed health and safety concerns about the production and use of nanoparticles, especially in areas of exposure monitoring, personal use, and environmental fate and transport. We suggest that stable isotopic tracers, which have been used widely in the earth sciences and in metabolic and other health-related studies for several decades, could be used to address many of these issues. One such example we are pursuing is the use of stable isotopes to monitor dermal absorption of zinc and titanium oxides in sunscreen preparations and other personal care products. Other potential applications of this tracing approach are discussed

A Critical Review of Biomarkers Used for Monitoring Human Exposure to Lead: Advantages, Limitations, and Future Needs

Lead concentration in whole blood (BPb) is the primary biomarker used to monitor exposure to this metallic element. The U.S. Centers for Disease Control and Prevention and the World Health Organization define a BPb of 10 μg/dL (0.48 μmol/L) as the threshold of concern in young children. However, recent studies have reported the possibility of adverse health effects, including intellectual impairment in young children, at BPb levels < 10 μg/dL, suggesting that there is no safe level of exposure. It appears impossible to differentiate between low-level chronic Pb exposure and a high-level short Pb exposure based on a single BPb measurement; therefore, serial BPb measurements offer a better estimation of possible health outcomes. The difficulty in assessing the exact nature of Pb exposure is dependent not so much on problems with current analytical methodologies, but rather on the complex toxicokinetics of Pb within various body compartments (i.e., cycling of Pb between bone, blood, and soft tissues). If we are to differentiate more effectively between Pb stored in the body for years and Pb from recent exposure, information on other biomarkers of exposure may be needed. None of the current biomarkers of internal Pb dose have yet been accepted by the scientific community as a reliable substitute for a BPb measurement. This review focuses on the limitations of biomarkers of Pb exposure and the need to improve the accuracy of their measurement. We present here only the traditional analytical protocols in current use, and we attempt to assess the influence of confounding variables on BPb levels. Finally, we discuss the interpretation of BPb data with respect to both external and endogenous Pb exposure, past or recent exposure, as well as the significance of Pb determinations in human specimens including hair, nails, saliva, bone, blood (plasma, whole blood), urine, feces, and exfoliated teeth

Windblown Lead Carbonate as the Main Source of Lead in Blood of Children from a Seaside Community: An Example of Local Birds as “Canaries in the Mine”

Background: In late 2006, the seaside community in Esperance, Western Australia, was alerted to thousands of native bird species dying. The source of the lead was thought to derive from the handling of Pb carbonate concentrate from the Magellan mine through the port of Esperance, begun in July 2005. Concern was expressed for the impact of this process on the community. Objective: This study was designed to evaluate the source of Pb in blood of a random sample of the community using Pb isotope ratios. Methods: The cohort comprised 49 children (48 20 years of age) with a bias toward higher blood lead (PbB) values to facilitate source identification. Results: Mean PbB level of the children was 7.5 μg/dL (range, 1.5-25.7 μg/dL; n = 49; geometric mean, 6.6 μg/dL), with four children whose PbB was > 12 μg/dL. The isotopic data for blood samples lay around two distinct arrays. The blood of all children analyzed for Pb isotopes contained a contribution of Pb from the Magellan mine, which for young children ranged from 27% up to 93% (mean, 64%; median, 71%). Subtraction of the ore component gave a mean background PbB of 2.3 μg/dL. Several children whose PbB was > 9 μg/dL and most of the older subjects have complex sources of Pb. Conclusions: The death of the birds acted as a sentinel event; otherwise, the exposure of the community, arising from such a toxic form of Pb, could have been tragic. Isotopic data and mineralogic and particle size analyses indicate that, apart from the recognized pathway of Pb exposure by hand-to-mouth activity in children, the inhalation pathway could have been a significant contributor to PbB for some of the very young children and in some parents.7 page(s

Preconception Brief: Occupational/Environmental Exposures

In the last decade, more than half of U.S. children were born to working mothers and 65% of working men and women were of reproductive age. In 2004 more than 28 million women age 18–44 were employed full time. This implies the need for clinicians to possess an awareness about the impact of work on the health of their patients and their future offspring. Most chemicals in the workplace have not been evaluated for reproductive toxicity, and where exposure limits do exist, they were generally not designed to mitigate reproductive risk. Therefore, many toxicants with unambiguous reproductive and developmental effects are still in regular commercial or therapeutic use and thus present exposure potential to workers. Examples of these include heavy metals, (lead, cadmium), organic solvents (glycol ethers, percholoroethylene), pesticides and herbicides (ethylene dibromide) and sterilants, anesthetic gases and anti-cancer drugs used in healthcare. Surprisingly, many of these reproductive toxicants are well represented in traditional employment sectors of women, such as healthcare and cosmetology. Environmental exposures also figure prominently in evaluating a woman’s health risk and that to a pregnancy. Food and water quality and pesticide and solvent usage are increasingly topics raised by women and men contemplating pregnancy. The microenvironment of a woman, such as her choices of hobbies and leisure time activities also come into play. Caregivers must be aware of their patients’ potential environmental and workplace exposures and weigh any risk of exposure in the context of the time-dependent window of reproductive susceptibility. This will allow informed decision-making about the need for changes in behavior, diet, hobbies or the need for added protections on the job or alternative duty assignment. Examples of such environmental and occupational history elements will be presented together with counseling strategies for the clinician

Seasonality and trend in blood lead levels of New York State children

BACKGROUND: Environmental exposure to lead remains a significant health problem for children. The costs of lead exposure in children are estimated to be considerably more than other childhood diseases of environmental origin. While long-term trends in blood lead levels (BLLs) among children are declining, seasonal variation persists. Cross-sectional studies have found a peak in summer months. Part of this variation may be due to increased exposure to lead paint on window sills and through increased contact with soils containing lead during the summer. The current study represents the largest published population-based study on seasonality and trends in the BLLs of children to date. In addition, the results offer a comparison of recent data on seasonality of BLLs in New York State children, to studies conducted over the past three decades. METHODS: 262,687 New York State children born between 1994 and 1997 were screened for blood lead within 2 weeks of their first or second birthdays. Time series analyses of blood lead data from these children were conducted to study the seasonality and trends of BLLs. RESULTS: Children's blood lead values showed a distinct seasonal cycle on top of a long-term decreasing trend. The geometric mean BLL declined by about 24% for children born between 1994 and 1997. The prevalence of elevated BLLs in two-year-olds was almost twice that in one-year-olds over the time period. Nearly twice as many children had elevated BLLs in the late summer compared to late winter/early spring. In this and previous cross-sectional studies, the amount of seasonality as a proportion of the mean ranged between 15% and 30%. CONCLUSION: Pediatricians should be aware of the seasonality of BLLs. For example, if a two-year-old receives a borderline result during the winter, it is possible that the levels would have been higher if he had been tested during the summer. However, physicians should continue to screen children at their normally scheduled well-child visits rather than delaying until summertime and possibly postponing the discovery of an elevated BLL. Age, season, and time trends still need to be considered in lead studies and result interpretation

Infantile zinc deficiency: Association with autism spectrum disorders

Elucidation of the pathogenesis and effective treatment of autism spectrum disorders is one of the challenges today. In this study, we examine hair zinc concentrations for 1,967 children with autistic disorders (1,553 males and 414 females), and show considerable association with zinc deficiency. Histogram of hair zinc concentration was non-symmetric with tailing in lower range, and 584 subjects were found to have lower zinc concentrations than −2 standard deviation level of its reference range (86.3–193ppm). The incidence rate of zinc deficiency in infant group aged 0–3 year-old was estimated 43.5 % in male and 52.5 % in female. The lowest zinc concentration of 10.7 ppm was detected in a 2-year-old boy, corresponding to about 1/12 of the control mean level. These findings suggest that infantile zinc deficiency may epigenetically contribute to the pathogenesis of autism and nutritional approach may yield a novel hope for its treatment and prevention