Environews
NIEHS NEWS | NTP Draft Brief on DEHP
Chances are most of us at one time or another have benefited from the convenience of DEHP-softened plastics, which are used in such products as building materials, food packaging, and medical devices. Despite this chemical's usefulness, experts are concerned that exposure to leached DEHP, especially among newborns and infants undergoing certain medical procedures, could lead to adverse reproductive and developmental effects. Now the National Toxicology Program is preparing to publish its latest assessment of these risks and the commentary surrounding them, as described in this article (p. A580).
FOCUS | Caring for Children Amidst Chaos: Guidelines to Maintain Health
In times of natural disaster, war, and other humanitarian crises, it is usually children who are most vulnerable to health-related consequences. Relief agencies provide crucial health care for children placed in harm's way, but the focus and application of this assistance can vary widely from agency to agency. A new report by the National Research Council advocates establishing a universal set of clinical guidelines and standards that could help improve the efficiency and impact of these aid organizations. This article (p. A584) takes a look at the challenges and potential benefits of creating such guidelines.
SPHERES OF INFLUENCE | Registering Skepticism: Does the EPA's Pesticide Review Protect Children?
Over the last 10 years, the EPA has been reassessing all food-use pesticides to ensure they meet safety standards set forth in the Food Quality Protection Act. In August, the agency declared success in its goal of prohibiting the use of hazardous compounds in pest control. But some environmental health advocates and activists are concerned that the EPA's review was not comprehensive enough, and that in approving the use of certain controversial pesticides the agency did not adequately consider the risks to particularly susceptible populations such as infants and children. This article (p. A592) discusses the actions arising from the review and examines the potential lapses pointed out by critics.
INNOVATIONS | Embryonic Insight: Mouse Histology in 3-D
Mouse histology has contributed immensely to our body of medical and genetic knowledge. Now one research team is seeking to advance the potential of this methodology even further by developing a simple, speedy procedure that combines ultra–high resolution/microscopic computed tomography scans with high-tech computer protocols. This article (p. A596) describes this new process, which yields three-dimensional computer images of mouse embryos for a more detailed look at genetic and environmental effects on tissues.
Commentaries
CHILDREN'S HEALTH | Social Ecology and Children's Development
The outcomes of exposure to neurotoxic chemicals early in life depend on the properties of both the chemical and the host's environment. When the questions focus on the toxicant, the environmental properties tend to be regarded as marginal and designated as covariates or confounders. Such approaches blur the reality of how the early environment establishes enduring biologic substrates. Weiss and Bellinger (p. 1479) describe another perspective, based on decades of biopsychological research on animals, that shows how the early, even prenatal, environment creates permanent changes in brain structure and chemistry and behavior.
NANOTECHNOLOGY | Nanoparticles and Isotope Tracers
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. Gulson and Wong (p. 1486) suggest that stable isotopic tracers—used widely in the earth sciences and in metabolic and other health-related studies—could be used to address many of these issues. For example, stable isotopes are currently used to monitor dermal absorption of zinc and titanium oxides in sunscreen preparations and other personal care products. The authors discuss other potential applications of this tracing approach.
Review
EXPOSURE ASSESSMENT | Exposure To Indoor Ozone and Its Reaction Products
The associations between outdoor ozone concentrations and both morbidity and mortality may be partially due to indoor exposures to ozone and ozone-initiated oxidation products. Weschler (p. 1489) examines the contributions of such indoor exposures to overall ozone-related health effects by extensive review of the literature as well as further analyses of published data. Daily inhalation intakes of indoor ozone are estimated to be 25–60% of total daily ozone intake. Indoor exposures to ozone and its oxidation products can be reduced by filtering ozone from ventilation air and limiting the indoor use of products and materials whose emissions react with ozone.
Research
ENVIRONMENTAL TOXICOLOGY | Endocrine Parameters and Heavy Metals in Storks
Endocrine parameters can detect early or low-level responses to pollutants. Although most of the studies on endocrine modulation have been focused on processes involving gonadal steroids, contaminants may target other parts of the endocrine system. Baos et al. (p. 1497) examined the adrenocortical stress response and thyroid hormone status in free-living nestling white storks in relation to heavy metals and arsenic levels in blood. The results suggest that birds exposed to sublethal lead levels may be at risk through an altered adrenocortical stress response, and support the idea that hypothalamus–pituitary–adrenal axis-related end points might be useful indicators of metal exposure and potential toxicity in wild animals.
EXPOSURE ASSESSMENT | Saxitoxins in Pyrodinium bahamense in the United States
From 2002 to 2004, 28 puffer fish poisoning (PFP) cases in Florida, New Jersey, Virginia, and New York were linked to the Indian River Lagoon in Florida. Saxitoxins of unknown source were first identified in fillet remnants. Associated with fatal paralytic shellfish poisoning (PSP) in the Pacific but not known to be toxic in the western Atlantic, the dinoflagellate Pyrodinium bahamense is an emerging public health threat. Landsberg et al. (p. 1502) propose characterizing this food poisoning syndrome as saxitoxin puffer fish poisoning to distinguish it from PFP, which is traditionally associated with tetrodotoxin, and from PSP caused by saxitoxins in shellfish.
CANCER | Mortality and Occupational PCB Exposure
Prince et al. (p. 1508) expanded an existing cohort of workers considered highly exposed to polychlorinated biphenyls (PCBs) at two capacitor-manufacturing plants to include all workers with at least 90 days of potential PCB exposure during 1939–1977. Causes of death of a priori interest included liver and rectal cancers, non-Hodgkin lymphoma, melanoma, and breast, brain, intestine, stomach, and prostate cancers. The study corroborates previous studies showing increased liver cancer mortality, but does not clearly associate rectal, stomach, and intestinal cancers with PCB exposure. This is the first PCB cohort showing a strong exposure–response relationship for prostate cancer mortality.
EXPOSURE ASSESSMENT | PBDE in U.S. Market Basket Survey and Dietary Intake
Schecter et al.'s study (p. 1515) expands a previously reported U.S. market basket survey using a larger sample size, and estimates levels of polybrominated diphenyl ether (PBDE) intake from food for the U.S. general population by sex and age. In food samples, concentrations of total PBDEs were varied. Fish were highest in PBDEs, followed by meat and dairy products. Adult females had lower dietary intake of PBDEs than did adult males. Dietary exposure alone does not appear to account for the very high body burdens measured. The indoor environment (dust, air) may play an important role in PBDE body burdens in addition to food.
Also see Science Selections, p. A600
RISK ASSESSMENT | Cancer and Dicamba Exposure
Dicamba is an herbicide commonly applied to crops in the United States and abroad. Samanic et al. (p. 1521) evaluated cancer incidence among pesticide applicators exposed to dicamba in the Agricultural Health Study, a prospective cohort of licensed pesticide applicators in North Carolina and Iowa. Detailed pesticide exposure information was obtained through a self-administered questionnaire. Exposure was not associated with overall cancer incidence, nor were there strong associations with any specific type of cancer. Although associations between exposure and lung and colon cancer were observed, the researchers did not find clear evidence for an association between dicamba exposure and cancer risk.
CANCER | Nitrate Intake and Bladder Cancer
N-Nitroso compounds, endogenously formed from nitrate-derived nitrite, are suspected to be important bladder carcinogens. However, the association between nitrate exposure from food or drinking water and bladder cancer has not been substantially investigated in epidemiologic studies. Zeegers et al. (p. 1527) evaluated the associations between nitrate exposure and bladder cancer in the Netherlands Cohort Study. Information on nitrate from diet was collected via a food frequency questionnaire in 1986 and a database on nitrate content of foods. Although the association between nitrate exposure and bladder cancer risk is biologically plausible, the results do not support such an association.
RISK CHARACTERIZATION | Public Health Impact of ELF
The association between exposure to extremely low-frequency electric and magnetic fields (ELF) and childhood leukemia has led to the classification of magnetic fields by the International Agency for Research on Cancer as a "possible human carcinogen." The fraction of childhood leukemia cases attributable to ELF exposure across the globe appears to be small. There remain, however, a number of uncertainties in these fraction estimates, particularly in the exposure distributions. Although a causal relationship between the two has not been established, Kheifets et al. (p. 1532) present estimates of the possible public health impact using attributable fractions to provide a potentially useful input into policy analysis under different scenarios.
RISK ASSESSMENT | Blood Lead Levels and Mortality Risk, NHANES III
Analyses of mortality data in the second National Health and Nutrition Examination Survey (NHANES II) suggested an increased risk of mortality at blood lead levels > 20 µg/dL. Blood lead levels have decreased markedly since the late 1970s. In NHANES III, conducted during 1988–1994, few adults had levels > 20 µg/dL. Schober et al. (p. 1538) studied the risk of mortality in relation to lower blood lead levels observed for adult participants of NHANES III. In a nationally representative sample, blood lead levels as low as 5–9 µg/dL were associated with an increased risk of death from all causes, cardiovascular disease, and cancer.
NEURODEVELOPMENT | Organophosphate Developmental Neurotoxicity
In the developing brain, serotonin (5HT) systems are among the most sensitive to disruption by organophosphates. Slotkin et al. (p. 1542) exposed neonatal rats to daily doses of diazinon or parathion on postnatal days 1–4 and evaluated 5HT receptors and the 5HT transporter in the brainstem and forebrain on postnatal day 5, using doses below the maximum tolerated dose and spanning the threshold for cholinesterase inhibition. At these doses, diazinon evoked up-regulation of 5HT1A and 5HT2 receptor expression, a pattern similar to that reported for chlorpyrifos, but parathion decreased 5HT1A receptor. Diazinon caused a decrease in the 5HT transporter in the brainstem and an increase in the forebrain, a pattern typical of damage of nerve terminals and reactive sprouting, whereas parathion had smaller, nonsignificant effects. These results support the idea that, in the developing brain, specific neurotransmitter systems are targeted differently by various organophosphates and without the requirement for cholinesterase inhibition, the supposed common mechanism of action.
NEURODEVELOPMENT | Folate Genes Associated with NTDs
Folate metabolism pathway genes have been examined for association with neural tube defects (NTDs) because folic acid supplementation reduces the risk of these debilitating birth defects. Boyles et al. (p. 1547) evaluate several folate pathway genes for association with human NTDs incorporating an environmental cofactor, maternal folate supplementation. Only single nucleotide polymorphisms (SNPs) in BHMT (betaine-homocysteine methyltransferase) were significantly associated in the overall data set; this significance was strongest when mothers took folate-containing nutritional supplements before conception. Further investigation of folate and methionine cycle genes will require extensive SNP genotyping and/or resequencing to identify novel variants, inclusion of environmental factors, and investigation of gene–gene interactions in large data sets.
Also see Science Selections, p. A601
Environmental Medicine
RISK CHARACTERIZATION | Persistence of Gulf War Symptoms
Of the approximately 700,000 U.S. troops deployed to the Persian Gulf during the 1990–1991 Gulf War, approximately 100,000 have presented medical complaints. Widespread symptomatic illness without defining physical features has been reported. Ozakinci et al. (p. 1553) ascertained changes in symptom status between an initial 1995 evaluation and a follow-up in 2000. As a whole, no significant changes in symptom number or severity were found. Those initially more symptomatic showed some improvement, but remained more highly symptomatic than those with lesser initial symptomatology. The symptom outbreak following the Gulf War has not abated over time, suggesting substantial need for better understanding and care for these veterans.
Children's Health
CANCER | Cancer Risk Assessment of Inner-City Teenagers
The Toxics Exposure Assessment Columbia–Harvard project assessed exposures and cancer risks from urban air pollutants in high school teenagers in New York and Los Angeles. Sax et al. (p. 1558) report that most volatile organic compounds had median upper-bound lifetime cancer risks that exceeded the U.S. Environmental Protection Agency (EPA) benchmark of 1 TIMES 10–6 and were generally greater than modeled estimates, more for compounds with predominant indoor sources. Chromium, nickel, and arsenic had median personal cancer risks above the U.S. EPA benchmark with exposures largely from outdoors and other microenvironments. The U.S. EPA–modeled concentrations tended to overestimate cancer risks for beryllium and chromium but underestimate risks for nickel and arsenic.
Also see Science Selections, p. A601
ASTHMA | Swimming Pools and Childhood Asthma
The pool chlorine hypothesis postulates that the increase in childhood asthma in the developed world could result at least partly from the increasing exposure of children to toxic gases and aerosols contaminating the air of indoor chlorinated pools. Bernard et al. (p. 1567) explored the relationships between childhood asthma, atopy, and cumulated pool attendance. Observed effects were dose related and most strongly linked to pool attendance before 6–7 years of age. Use of indoor chlorinated pools, especially by young children, may interact with atopic status to promote the development of childhood asthma. The findings implicate pool chlorine in the increase of childhood asthma in industrialized countries.
Also see Science Selections, p. A600
ASTHMA | Home Moisture Remediation for Childhood Asthma
Home dampness and the presence of mold and allergens have been associated with asthma morbidity. Kercsmar et al. (p. 1574) examined changes in children's symptoms as a result of home remediation. Children in both groups showed improvement in asthma symptomatic days during the preremediation portion of the study. The remediation group had a significant decrease in symptom days after remodeling, whereas the control group did not significantly change. In the postremediation period, the remediation group had a lower rate of exacerbations. Construction remediation aimed at the root cause of moisture sources and combined with a medical/behavioral intervention significantly reduces symptom days and health care visits.
EXPOSURE ASSESSMENT | PBDE Concentrations in a U.S. Family
Polybrominated diphenyl ethers (PBDEs), a major class of flame retardants, are ubiquitous environmental contaminants found in particularly high concentrations in humans from the United States. Fischer et al. (p. 1581) compared PBDE concentrations in blood samples drawn from a family; serum samples collected at two sampling occasions 90 days apart were analyzed for PBDE congeners. The estimates indicate that house dust contributes to higher PBDE levels in children. This case study suggests that children are at higher risk for PBDE exposures and, accordingly, face higher risks of PBDE-related health effects than adults.
POPULATION HEALTH | Economic Impact of Early Life ETS Exposure
Early-life exposure to environmental tobacco smoke (ETS) can result in developmental delays as well as childhood asthma and increased risk of cancer. Using the environmentally attributable fraction approach, Miller et al. (p. 1585) estimated the annual cost of one aspect of ETS-related developmental delay, early intervention services. The estimated cost of these services due to ETS exposure is > $50 million/year for New York City Medicaid births and $99 million for all births. The high annual cost of a single aspect of developmental delay due to prenatal exposure to ETS provides further impetus for increased prevention efforts.
FETAL DEVELOPMENT | Agricultural Pesticide Use and Hypospadias
Meyer et al. (p. 1589) assessed the relationship between hypospadias and proximity to agricultural pesticide applications using a GIS-based exposure method. Information was obtained for cases born between 1998 and 2002 in eastern Arkansas, and controls were selected from birth certificates. Exposure was based on pounds of pesticides applied (estimated by crop type) or persisting within 500 m of each subject's home during gestational weeks 6 to 16. Except for diclofop-methyl, the authors found no evidence that estimated exposure to pesticides known to have reproductive, developmental, or endocrine-disrupting effects causes increased risk of hypospadias. Further research on the potential effects of exposure to diclofop-methyl is recommended.
METABOLISM | Dioxin Elimination Half-Life in Seveso Children
Kerger et al. (p. 1596) performedpharmacokinetic and statistical analyses to elucidate key variables affecting 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) elimination in children and adolescents. Blood was collected from residents of Seveso, Italy, who were < 18 years of age at the time of a nearby trichlorophenol reactor explosion in 1976. The researchers found that children and adolescents have shorter TCDD half-lives and a slower rate of increase in half-life than adults, and this effect is augmented at higher body burdens. Modeling of TCDD blood concentrations or body burdens should take into account the markedly shorter elimination half-life in children and adolescents and concentration-dependent effects in persons > 400–700 ppt.
Mini-Monograph
ETHICS | Ethics in Children's Environmental Health Research
The consideration of ethical issues relating to pediatric environmental health is a recent phenomenon. In the late 1990s, researchers at the Kennedy Krieger Institute undertook a study to compare the effectiveness of several methods of reducing lead risk in housing. However, in Grimes v. Kennedy Krieger Institute, Inc., a Maryland court questioned the ethics of performing research on children when there is no prospect of direct benefit to those children and whether parents can consent to such research. In response to this case, the Children's Environmental Health Network held a working meeting to explore this topic. The articles in this mini-monograph (p. 1603) discuss ways in which these studies can be carried out while protecting research subjects and involving the community as active participants in research. The authors hope that the fruits of this workshop will inform the National Children's Study efforts and the efforts of others involved in children's environmental health research.
