Environews
FOCUS | Face to Face with Toy Safety: Understanding an Unexpected Threat
Acknowledging the connection between environmental interactions and our health has led to an increase in the scrutiny of more of the goods we use, which has in turn led to safety recalls. Following a spate of recalls in 2007 and 2008, lead-contaminated toys became one of the biggest environmental health stories of recent times. But lead isn't the only threat in the toybox. This article (p. A70) discusses some of the current safety issues playing out in the toy industry, and looks at the responses of various stakeholders.
SPHERES OF INFLUENCE | Room to Grow: Incentives Boost Energy-Efficient Homebuilding
Global trade has been booming in recent years, and shows no signs of slowing down. And while there are definite benefits that result from the steady movement of goods internationally, there are also negative consequences, one of which is the community-level human health impact of transporting those goods. This article (p. A78) takes a look at some of the adverse effects associated with goods movement, and describes local, national, and international mitigation efforts.
Reviews
REPRODUCTIVE HEALTH | Testicular Dysgenesis Syndrome Meta-Analysis
Male reproductive tract abnormalities such as hypospadias and cryptorchidism, testicular cancer, and impaired spermatogenesis have been proposed to comprise a common syndrome for which there is a common etiology resulting from the disruption of gonadal development during fetal life; this syndrome is termed the "testicular dysgenesis syndrome" (TDS). Martin et al. (p. 149) performed a quantitative meta-analysis of the association between the end points related to TDS and prenatal exposure to estrogenic agents. The doubling of the risk ratios for the end points investigated after DES exposure is consistent with a shared etiology and the TDS hypothesis, but does not constitute evidence of an estrogenic mode of action.
CARCINOGENESIS | Arsenic-Induced Prostate Cancer
In order to critically evaluate the etiologic role of inorganic arsenic in human prostate cancer, Benbrahim-Tallaa and Waalkes (p. 158) assessed data from relevant epidemiologic studies and laboratory studies. Many human studies provide clear evidence of a dose–response relationship between inorganic As and prostate cancer. Relevant whole-animal models that show a relationship between inorganic As and prostate cancer are not available; however, cellular model systems indicate that As can induce malignant transformation of human prostate epithelial cells in vitro. Arsenic also appears to affect prostate cancer cell progression by precipitating events leading to androgen independence in vitro.
Research
ENDOCRINE SYSTEM | Arsenic as an Endocrine Disruptor
Chronic exposure to excess arsenic in drinking water has been strongly associated with increased risks of multiple cancers, diabetes, heart disease, and reproductive and developmental problems in humans. Arsenic is a potent endocrine disruptor at low, environmentally relevant levels, and it alters steroid signaling at the level of receptor-mediated gene regulation for all five steroid receptors. Davey et al. (p. 165) determined whether As can also disrupt gene regulation via the retinoic acid receptor and/or thyroid hormone receptor and whether these effects are similar to previously observed effects on steroid regulation.
EXPOSURE ASSESSMENT | Predictors of Urinary Bisphenol A Concentrations
Bisphenol A (BPA) is used to manufacture polymeric materials, such as polycarbonate plastics, and is found in a variety of consumer products. Recent data show widespread BPA exposure among the U.S. population. Mahalingaiah et al. (p. 173) determined the temporal variability and predictors of BPA exposure. The authors found a nonsignificant increase in urinary BPA concentrations in women while pregnant compared with nonpregnant samples from the same women. Samples collected from partners on the same day were correlated, suggesting shared sources of exposure. Finally, a single urine sample showed moderate sensitivity for predicting a subject's tertile categorization.
POPULATION HEALTH | DDE and Length of Lactation
Higher levels of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), the major degradation product of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT), have been related to shorter duration of breast-feeding. If DDE truly shortens lactation, this has public health importance regarding infant mortality and the use of DDT for malaria control. Cupul-Uicab et al. (p. 179) assessed the relationship of maternal DDE concentrations with length of subsequent lactation. Data from a highly exposed area of Mexico did not support the hypothesis that exposure to DDE shortens length of lactation. The association seen in women who previously breast-fed was likely due to to a noncausal mechanism.
Also see Science Selections, p. A83
NEUROBEHAVIORAL DISEASE | Neurocognitive Change after Exposure to PCBs/PCDFs in Taiwan
In 1979, approximately 2,000 people were exposed to polychlorinated biphenyls (PCBs) and dibenzofurans (PCDFs) due to ingestion of contaminated cooking oil in Taiwan. Although delayed developmental milestones and poorer neurocognitive functioning has been reported in children born to exposed mothers, it is unclear whether impaired neurocognitive functioning occurred in people who were directly exposed. In a retrospective cohort study of subjects ≥ 60 years of age, Lin et al. (p. 184) compared neurocognitive functioning of people exposed to PCBs and PCDFs with that of their unexposed sex- and age-matched neighbors. Results show dose-dependent neurocognitive deficits in certain aspects of attention, visual memory, and learning ability in women previously exposed to PCBs and PCDFs, but not in exposed men.
RESPIRATORY DISEASE | Arsenic, CC16, and Respiratory Effects
Arsenic from drinking water has been associated with malignant and nonmalignant respiratory illnesses; however, this association has not been well established because the assessments of respiratory symptoms may be influenced by recall bias or by interviewer bias in participants with visible skin lesions. Parvez et al. (p. 190) examined the relationship of the serum level of Clara cell protein CC16 (a novel biomarker for respiratory illnesses) with well As, total urinary As, and urinary As methylation indices. The findings suggest that serum CC16 may be a useful biomarker of epithelial lung damage in individuals with arsenical skin lesions.
Also see Science Selections, p. A82
RISK ASSESSMENT | Long-Term Exposure to Air Pollution and Mortality
Several studies have shown an effect of between-city contrasts in long-term exposure to air pollution on mortality; however, the effect of within-city contrasts is still poorly understood. Beelen et al. (p. 196) investigated the association between long-term exposure to traffic-related air pollution and mortality in a Dutch cohort. Traffic-related air pollution and several traffic exposure variables were associated with mortality in the full cohort. Relative risks were generally small. Associations between natural cause and respiratory mortality were statistically significant for nitrogen dioxide and black smoke. These results add to the evidence that long-term exposure to ambient air pollution is associated with increased mortality.
MUTAGENESIS | HPRT Mutation in Butadiene-Exposed Workers
The carcinogenicity of 1,3-butadiene (BD), an important industrial chemical and an environmental and occupational pollutant, has been proven in rodents, but themolecular mechanism(s) of mutagenicity and carcinogenicity have not been elucidated in humans. To identify the characteristic mutations associated with BD exposure in the human HPRT gene, Liu et al. (p. 203) compared the mutation frequencies and exon deletions of BD-exposed workers with those of control subjects in China. Results suggest that BD should increase the frequency of large deletions of HPRT gene in human lymphocytes in BD-exposed workers.
NEUROBEHAVIORAL DISEASE | PCBs and Neuropsychological Status in Older Persons
Polychlorinated biphenyls (PCBs) may accelerate the cognitive and motor dysfunction found in normal aging, but few studies have examined these outcomes among adults exposed to PCBs. Fitzgerald et al. (p. 209) evaluated neuropsychological status and low-level PCB exposure among older adults living along contaminated portions of the upper Hudson River. The results suggest that among adults 55–74 years of age whose current body burdens are similar to those of the general population, PCB exposure may be associated with some measures of memory, learning, and depression.
EXPOSURE ASSESSMENT | Chlorination Disinfection By-Products and Congenital Anomalies
Several studies have shown that increased risk of various congenital anomalies is associated with trihalomethane (THM) exposure in the water supply. Nieuwenhuijsen et al. (p. 216) investigated the relationship between THM concentrations and risk of congenital anomalies in England and Wales. Data on congenital anomalies were obtained from the National Congenital Anomalies System, regional registries, and national terminations registry, and THM data were obtained from water companies. Through analyses using fixed- and random- effects models for broadly defined groups of anomalies, a more restricted set of anomalies, and for isolated and multiple anomalies, the authors found little evidence for a relationship between THM concentrations in drinking water and risk of congenital anomalies.
DEVELOPMENTAL BIOLOGY | Atrazine Exposure Alters Organogenesis
Exposure to anthropogenic chemicals during development can disrupt organ system morphogenesis. Previous studies have examined the effects of exposure to the herbicide atrazine during metamorphosis or early developmental stages of amphibians. To identify and characterize susceptibility during the often-overlooked developmental stage of organ morphogenesis, Lenkowsi et al. (p. 223) investigated the effects of atrazine in the Xenopus laevis amphibian model system. Results demonstrate that acute atrazine exposure during early organ morphogenesis disrupts proper organ development in this model.
CANCER | Arsenic in Drinking Water and Cancer in Denmark
Arsenic is a well-known carcinogen often found in drinking water. Increased cancer risks have been reported among individuals exposed to high As concentrations in drinking water, whereas results have been inconsistent in studies with low doses. In a study based on a Danish cohort, Baastrup et al. (p. 231) found no significant association between As exposure and risk for lung, bladder, liver, kidney, prostate, or colorectal cancer or melanoma skin cancer; however, the risk for nonmelanoma skin cancer decreased with increasing exposure. After adjusting for enrollment area, no association with nonmelanoma skin cancer was found.
Environmental Medicine
EXPOSURE ASSESSMENT | Human Exposure to Dioxins from Clay
As part of the University of Michigan Dioxin Exposure Study, Franzblau et al. (p. 238) measured selected polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls in serum from subjects in five Michigan counties. One subject, a 77-year-old woman, had a total toxic equivalency (TEQ) of 211 ppt (lipid-adjusted basis), the highest value observed in the study population. This subject had no reported source of food-related exposure to dioxin-like compounds; however, for at least 30 years she had lived on dioxin-contaminated property and had been a ceramics hobbyist. Results suggested that ceramic clay, particularly the process of firing clay in unvented kilns, can be a significant nonfood/nonindustrial source of human exposure.
Children's Health
NEURODEVELOPMENT | Blood Lead and IQ
Few studies have provided data that is directly relevant to the question of whether blood lead concentrations < 10 µg/dL adversely affect children's cognitive function. Using general linear and semiparametic models, Jusko et al. (p. 243) examined the association between blood lead concentrations assessed throughout early childhood and children's IQ at 6 years of age. Evidence indicates that children's intellectual functioning at 6 years of age is impaired by blood lead concentrations well below 10 µg/dL, the Centers for Disease Control and Prevention–defined level of elevated blood lead.
Also see Science Selections, p. A82
NEURODEVELOPMENT | Lead Exposure and Adrenocortical Functioning
Recent studies have demonstrated heightened reactivity of the hypothalamic–pituitary–adrenal (HPA) axis to acute stress in animals exposed to heavy metal contaminants, particularly lead. However, Pb-induced dysregulation of the HPA axis has not yet been studied in humans. Gump et al. (p. 249) examined children's cortisol response to acute stress (the glucocorticoid product of HPA activation) in relation to low-level prenatal and postnatal Pb exposure. Results suggest that relatively low prenatal and postnatal blood lead levels can alter children's adrenocortical responses to acute stress; however, behavioral and health consequences of this Pb-induced HPA dysregulation have yet to be determined.
Also see Science Selections, p. A83
BIOMONITORS | Children's Amalgam Exposure and Urinary Mercury
Urinary mercury (U-Hg) excretion is commonly used as a biomarker for Hg exposure from dental amalgam restorations. Maserejian et al. (p. 256) examined time-sensitive longitudinal amalgam exposure data in children to determine the most efficient measure of exposure in analyses concerning U-Hg. The current total of amalgam surfaces was the most robust predictor of current U-Hg, whereas posterior occlusal surface-years was the best predictor of cumulative U-Hg. One single measure of amalgam exposure is not sufficient. Studies of cumulative effects of Hg from amalgam exposure in children are likely to have improved validity and precision if time-sensitive amalgam exposure measures are used. In contrast, simple counts of current amalgam fillings are adequate to capture amalgam-related current U-Hg.
BIOMONITORS | Calcium Pump, Mercury, and Lead
Calcium homeostasis is a known target of several environmental toxicants including lead and mercury. Huel et al. (p. 263) investigated the relationship between Hg exposure and erythrocyte Ca pump activity in women at delivery and in their newborns by determining Pb and total Hg concentrations in hair and blood samples obtained at delivery. Basal and calmodulin-stimulated Ca pump activity was measured in red blood cells from cord blood and maternal erythrocyte plasma membranes. The findings confirm results from previous studies and support the use of biomarkers in newborns from the general population.