Environews
FOCUS | Environmental Connections: A Deeper Look into Mental Illness
In the past, mental illness was regarded with fear and uncertainty, largely because specific causes were unknown. But new advances in epidemiology and molecular biology have shed light on possible genetic triggers, which has in turn prompted questions regarding the role of the environment in its development. Just how does environment affect mental health? This article (p. A404) explores that question, and takes a look at some of the latest findings in psychiatric medicine that suggest a link between some environmental exposures and development of mental disease.
SPHERES OF INFLUENCE | A Change in the Air: Smoking Bans Gain Momentum Worldwide
As more information emerges linking secondhand smoke to cancer and other diseases, many local and national governments have stepped up clean air efforts such as bans on smoking in restaurants, workplaces, and other public areas. These measures have contributed to smoking declines and improved health rates in many developed nations, but antismoking advocates believe more action is needed in poorer countries where smoking is still aggressively marketed. This article (p. A412) discusses the worldwide move toward stricter antismoking legislation, and looks at how some pro-smoking strategies employed in the developing world are curtailing its momentum there.
Review
NANOTECHNOLOGY | Environmental Health Review of Carbon Nanotubes
Carbon nanotubes (CNTs), considered one of the most promising materials in nanotechnology, have attractive properties for many technologic applications. The different synthesis, purification, and postprocessing methods produce CNTs with different physical characteristics, which can be applied in different fields ranging from composite materials, medical applications, and electronics to energy storage. CNTs can be bioavailable to organisms, and the properties of CNTs suggest a possible accumulation along the food chain and high persistence. Helland et al. (p. 1125) reviewed toxicology studies of CNTs and note that the identification of possible risks to human health and environment is a prerequisite for a successful introduction of CNTs in future applications.
Research
POPULATION HEALTH | Vitamin D Insufficiency across Australian Populations
Inadequate sun exposure and dietary vitamin D intake can result in vitamin D insufficiency, but limited data are available on actual vitamin D status and predictors in healthy individuals in different regions and by season. van der Mei et al. (p. 1132) report that vitamin D insufficiency is common in winter and spring in three locations in Australia. Season appears more important than latitude, but both accounted for less than one-fifth of the variation in serum 24-hydroxyvitamin D levels, highlighting the importance of behavioral factors. Current sun exposure guidelines and dietary intake do not seem to fully prevent vitamin D insufficiency; thus, consideration should be given to modification of guidelines or pursuing other means to achieve vitamin D adequacy.
ASTHMA | Air Pollution and Violence in Asthma Etiology
Disproportionate life stress, with consequent physiologic alteration, has been proposed as a major pathway linking socioeconomic position, environmental exposures, and health disparities. Asthma disproportionately affects lower-income urban communities, where air pollution and social stressors may be elevated. Clougherty et al. (p. 1140) examined the role of exposure to violence as a chronic stressor in altering susceptibility to traffic-related air pollution in asthma etiology using geographic information system–based models to retrospectively estimate residential exposures to traffic-related pollution in 413 children. Results show an association between traffic-related air pollution and asthma among urban children exposed to violence.
Also see Science Selections, p. A416
EXPOSURE ASSESSMENT | Assessing Uncertainty in Spatial Air Pollution Models
Although many epidemiologic studies now use models of intraurban exposure, there has been little systematic evaluation of the performance of different models. Molitor et al. (p. 1147) propose a modeling framework for assessing exposure model performance and the role of spatial autocorrelation in health effects estimation. They used data obtained from an exposure measurement substudy of subjects from the Southern California Children's Health Study. Findings suggest that the inclusion of residual spatial error terms improves the prediction of health effects. The results also demonstrate how residual spatial error may be used as a diagnostic for comparing exposure model performance.
CARDIOVASCULAR DISEASE | Stress Modifies Lead Effect on Hypertension
Lead exposure and psychological stress have been independently associated with hypertension in various populations, and animal studies suggest that when they co-occur, their effects may be exacerbated. Peters et al. (p. 1154) examined whether psychological stress modifies the impact of cumulative lead exposure (measured as bone lead levels) on hypertension and blood pressure in Boston (Massachusetts) area community-exposed men participating in the Normative Aging Study. These are the first analyses to look at interactive effects of stress and lead on hypertension in humans. The results suggest that the effect of lead on hypertension is most pronounced among highly stressed individuals, independent of demographic and behavioral risk factors.
Also see Science Selections, p. A417
RISK ASSESSMENT | Ranking Cancer Risks of Hazardous Air Pollutants in the United States
Loh et al. (p. 1160) compared cancer risks from organic hazardous air pollutants (HAPs) based on total personal exposure summed across different microenvironments and exposure pathways. They developed distributions of personal exposure concentrations using field monitoring and modeling data for inhalation and, where relevant, ingestion pathways. Most of the polycyclic aromatic hydrocarbon, benzene, acetaldehyde, and 1,3-butadiene risk came from outdoor sources, whereas indoor sources were primarily responsible for chloroform, formaldehyde, and naphthalene risks. The infiltration of outdoor pollution into buildings, emissions from indoor sources, and uptake through food are all important to consider in reducing overall personal risk to HAPs.
REPRODUCTIVE HEALTH | Disinfection By-Products and Semen Quality
Chlorination of drinking water generates disinfection by-products (DBPs), which have been shown to disrupt spermatogenesis in rodents at high doses; this suggests that DBPs could pose a reproductive risk to men. Luben et al. (p. 1169) assessed DBP exposure and semen quality (sperm concentration and morphology, DNA integrity, and chromatin maturity) in a cohort of 228 men. Exposures to DBPs were evaluated by incorporating data on water consumption and bathing and showering with concentrations measured in tap water. The results do not support an association between exposure to DBPs at levels near or below regulatory limits and adverse sperm outcomes in humans.
Also see Science Selections, p. A416
EXPOSURE ASSESSMENT | Ultrafine Particles and Oxidative Damage to DNA
Particulate matter, especially ultrafine particles (UFPs), may cause health effects through generation of oxidative stress with resulting damage to DNA and other macromolecules. Bräuner et al. (p. 1177) investigated oxidative damage to DNA and related repair capacity in peripheral blood mononuclear cells during controlled exposure to urban air particles with assignment of number concentration to four size modes with average diameters of 12, 23, 57, and 212 nm. The results indicate that UFPs, especially the 57-nm soot fraction from vehicle emissions, causes systemic oxidative stress with damage to DNA and no apparent compensatory up-regulation of DNA repair within 24 hr.
EXPOSURE ASSESSMENT | Pesticides in Drinking Water
Human health anomalies have been associated with pesticide exposure for people living in rural areas the northern Great Plains of North America. Donald et al. (p. 1183) investigated the occurrence of 45 pesticides in drinking water from reservoirs in this area that received water primarily from snowmelt and rainfall runoff from agricultural crop lands. Two insecticides and 27 herbicides were detected in reservoir water. For the 7 herbicides with established drinking water guidelines, all concentrations of the individual chemicals were well below their respective guidelines; however, guidelines have not been established for mixtures of pesticides.
RISK CHARACTERIZATION | Mortality in the Unionized U.S. Trucking Industry
Occupational and population-based studies have related exposure to fine particulate air pollution, and specifically particulate matter from vehicle exhausts, to cardiovascular diseases and lung cancer. Laden et al. (p. 1192) established a large retrospective cohort to assess mortality in the unionized U.S. trucking industry to investigate mortality patterns associated with job-specific exposures. They examined rates of cause-specific mortality compared with the general U.S. population. Results of this detailed assessment of specific job categories in the U.S. trucking industry showed an excess of mortality due to lung cancer and ischemic heart disease, particularly among drivers.
ENDOCRINE SYSTEM | Thyroid Function and PCBs, Dioxins, and DDE in Adults
Thyroid hormone homeostasis can be disrupted by exposure to ubiquitous and bioaccumulative organochlorines such as polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins. Investigations of health effects have generally focused on human populations with relatively high exposures through occupation, accident, or high fish consumption, but general population exposures may also carry risk. Turyk et al. (p. 1197) show a dose-dependent decrease in total thyroxine with exposure to dioxin-like toxic equivalents at levels similar to those found in the general U.S. population. The effects were stronger in women. Results suggest that older adults may be more at risk for disruption of thyroid hormone homeostasis by organochlorines than younger adults.
CARDIOVASCULAR DISEASE | POPs and Cardiovascular Diseases
There is increasing evidence that exposure to persistent organic pollutants (POPs) can contribute to the development of inflammatory diseases such as atherosclerosis. Ha et al. (p. 1204) examined associations of serum concentrations of POPs with self-reported history of cardiovascular disease (CVD). The authors investigated cross-sectional associations of serum POPs concentrations with the prevalence of self-reported CVD in 889 adults ≥ 40 years of age in the National Health and Nutrition Examination Survey, 1999–2002. Dioxin-like polychlorinated biphenyls (PCBs), nondioxin-like PCBs, and organochlorine pesticides were positively associated with the prevalence of CVD only among females. Polychlorinated dibenzo-p-dioxins showed positive trends with the prevalence of CVD in both males and females.
GENE POLYMORPHISM | HFE Polymorphisms and Lead on Cognitive Decline
Because iron and lead promote oxidative damage and HFE gene polymorphisms increase body iron burden, HFE variant alleles may modify the relationship between lead burden and cognitive decline. Wang et al. (p. 1210) assessed the modifying effects of HFE variants on the lead burden–cognitive decline relationship in participants of the Normative Aging Study, a longitudinal study of community-dwelling men from greater Boston, Massachusetts. Participants were measured for lead using K-X-ray fluorescence, assessed for cognitive function with the Mini-Mental State Examination, and genotyped for HFE polymorphisms. Results suggest that HFE polymorphisms significantly modify the association between lead burden and the rate of cognitive decline.
INFECTIOUS DISEASE | Environmental Determinants of Infectious Disease
Because of the increasing number of identified emerging and re-emerging pathogens, there is an urgent need to understand how environmental change affects disease burden. Eisenberg et al. (p. 1216) present a framework that provides a context from which to examine the relationship between environmental changes and disease transmission, and a structure from which to unite disparate pieces of information coming from a variety of disciplines. The framework explicitly expresses the problem at a systems level that goes beyond the traditional risk factor analysis used in public health, and the matrix provides a means to explicitly express the coupling of different system components.
RISK ASSESSMENT | Genetic Variation in Blood Lead
Lead is an environmental pollutant that causes acute and chronic toxicity. Mean blood lead concentrations have been shown to be related to exogenous sources such as industrial activity, use of lead-based paints, and traffic density. However individual differences in lead absorption, distribution, and toxicity, and of genetic causes of such variation have not been fully investigated. Whitfield et al. (p. 1224) assessed the genetic contribution to variation in blood lead concentration in adults and conducted a preliminary search for genes that produce such variation. After adjusting for these covariates, the authors found strong evidence of genetic effects but not for shared environmental effects persisting into adult life.
GENE POLYMORPHISM | NER and Arsenic Interactions in Skin Cancer
Arsenic exposure may alter the efficiency of DNA repair. Ultraviolet radiation damage is specifically repaired by nucleotide excision repair (NER), and common genetic variants in NER may increase risk for non-melanoma skin cancer (NMSC). Applebaum et al. (p. 1231) tested whether polymorphisms in the NER genes XPA (A23G) and XPD (Asp312Asn and Lys751Gln) modify the association between arsenic and NMSC in incident cases of basal and squamous cell carcinoma identified in New Hampshire. The findings indicate a reduced NMSC risk in relation to XPD Asp312Asn and Lys751Gln variants. These data support the hypothesis that NER polymorphisms may modify the association between NMSC and arsenic.
Environmental Medicine
HUMAN TOXICOLOGY | Uranium in Well Water
Magdo et al. (p. 1237) present the case of a family of seven residing in rural northwestern Connecticut who discovered elevated concentrations of uranium in their drinking water. Concentrations were well above the U.S. Environmental Protection Agency maximum contaminant level for uranium in public water supplies. The source of the uranium was groundwater from the Brookfield Gneiss, a geologic formation known to contain uranium. This case underscores the hazards of consuming groundwater from private wells, documents the potential for significant residential exposure to naturally occurring uranium in well water, and highlights the special sensitivity of young children to residential environmental exposures.
Children's Health
K-12 EDUCATION | Childhood Blood Lead Levels and Educational Outcomes
Childhood lead poisoning remains a critical environmental health concern. To determine whether lead levels in early childhood are related to educational achievement as measured by performance on end-of-grade (EOG) testing, Miranda et al. (p. 1242) linked test data for 4th-grade students to blood lead surveillance data for seven North Carolina counties. They found that discernible impact of blood lead levels on EOG testing is demonstrated for early childhood blood lead levels as low as 2 µg/dL; a blood lead level of 5 µg/dL is associated with a decline in reading and mathematics scores. Early childhood lead exposures appear to have more impact on performance on the reading than on the mathematics portions of the tests.
Also see Science Selections, p. A417
EXPOSURE ASSESSMENT | Air Pollution and Endothelin-1
Controlled exposures of animals and humans to particulate matter (PM) or ozone air pollution cause an increase in plasma levels of endothelin-1 (ET-1), a potent vasoconstrictor that regulates pulmonary arterial pressure. Calderón-Garcidueñas et al. (p. 1248) performed clinical histories, physical examinations, and complete blood counts on 81 children to determine whether Mexico City children, who are chronically exposed to PM and ozone levels that exceed U.S. air quality standards, have elevated plasma ET-1 levels and pulmonary arterial pressures. ET-1 levels in Mexico City children were positively correlated with daily outdoor hours and 7-day cumulative levels of PM < 2.5 µm in aerodynamic diameter before ET-1 measurement.
HUMAN TOXICOLOGY | Farmworker Child Pesticide Metabolite Levels
To document the pesticide urinary metabolite levels of farmworker children in North Carolina, determine the number of different metabolites detected for each child, and delineate risk factors associated with the number of metabolites, Arcury et al. (p. 1254) analyzed urine samples collected from 60 Latino farmworker children 1–6 years of age (34 female, 26 male). Because children in farmworker homes experience multiple sources of pesticide exposure and because pesticides may remain in their environments for long periods, environmental and occupational health changes are needed to address these exposures.
