Chromium VI and stomach cancer: a meta-analysis of the current epidemiological evidence.

Objectives: Chromium VI (hexavalent chromium, Cr(VI)) is an established cause of lung cancer, but its association with gastrointestinal cancer is less clear. The goal of this study was to examine whether the current human epidemiological research on occupationally inhaled Cr(VI) supports the hypothesis that Cr(VI) is associated with human stomach cancer.

Methods: Following a thorough literature search and review of individual studies, we used meta-analysis to summarise the current epidemiological literature on inhaled Cr(VI) and stomach cancer, explore major sources of heterogeneity, and assess other elements of causal inference.

Methodological considerations in screening for cumulative environmental health impacts: lessons learned from a pilot study in California.

Polluting facilities and hazardous sites are often concentrated in low-income communities of color already facing additional stressors to their health. The influence of socioeconomic status is not considered in traditional models of risk assessment. We describe a pilot study of a screening method that considers both pollution burden and population characteristics in assessing the potential for cumulative impacts.

Bisphenol A: developmental toxicity from early prenatal exposure.

Bisphenol A (BPA) exposure has been documented in pregnant women, but consequences for development are not yet widely studied in human populations. This review presents research on the consequences for offspring of BPA exposure during pregnancy. Extensive work in laboratory rodents has evaluated survival and growth of the conceptus, interference with embryonic programs of development, morphological sex differentiation, sex differentiation of the brain and behavior, immune responsiveness, and mechanism of action.

Beyond risk assessment: principles for assessing community impacts.

Risk assessment methods have evolved over time to become better at evaluating risks associated with single chemical exposures, yet are limited in evaluating risks faced by communities with exposures to a range of chemical hazards via multiple routes. Recognizing the need to identify better approaches to assess disparate impacts facing certain populations due to environmental pollution, the authors evaluated activities within the Office of Environmental Health Hazard Assessment (in California's Environmental Protection Agency) that had begun addressing these concerns by moving beyond standard risk assessment practices. On the basis of these examples, the authors identify 4 overarching principles to guide community assessments and explore how their application can improve these assessments.

A blood lead benchmark for assessing risks from childhood lead exposure.

Lead exposure is an insidious problem, causing subtle effects in children at low exposure levels where clinical signs are not apparent. Although a target blood lead concentration (Pb(B)) of ten micrograms per deciliter (10 microg/dL) has been used as the basis for environmental decision-making in California for nearly two decades, recent epidemiologic evidence suggests a relationship between cognitive deficits and Pb(B) at concentrations < 10 microg/dL. Based on a published meta-analysis of children's IQ scores and their blood lead concentrations, we developed a new blood lead benchmark: an incremental increase in blood lead concentration (DeltaPb(B)) of 1 microg/dL, an increase that we estimate could decrease the IQ score in an average school child in California by up to one point.

Cancer mortality in a Chinese population exposed to hexavalent chromium in drinking water.

Background: In 1987, investigators in Liaoning Province, China, reported that mortality rates for all cancer, stomach cancer, and lung cancer in 1970-1978 were higher in villages with hexavalent chromium (Cr+6)-contaminated drinking water than in the general population. The investigators reported rates, but did not report statistical measures of association or precision.

Methods: Using reports and other communications from investigators at the local Jinzhou Health and Anti-Epidemic Station, we obtained data on Cr+6 contamination of groundwater and cancer mortality in 9 study regions near a ferrochromium factory.

Evaluation and application of the RD50 for determining acceptable exposure levels of airborne sensory irritants for the general public.

Background: The RD(50) (exposure concentration producing a 50% respiratory rate decrease) test evaluates airborne chemicals for sensory irritation and has become an American Society for Testing and Materials (ASTM) standard method. Past studies reported good correlations (R(2)) between RD(50)s and the occupational exposure limits, particularly threshold limit values (TLVs).

Objective: The main purpose of this study was to examine the relationship between RD(50)s and human sensory irritation responses in a quantitative manner, particularly for chemicals that produce burning sensation of the eyes, nose, or throat, based on lowest observed adverse effect levels (LOAELs) reported for human subjects.

Development of a health-protective drinking water level for perchlorate.

We evaluated animal and human toxicity data for perchlorate and identified reduction of thyroidal iodide uptake as the critical end point in the development of a health-protective drinking water level [also known as the public health goal (PHG)] for the chemical. This work was performed under the drinking water program of the Office of Environmental Health Hazard Assessment of the California Environmental Protection Agency. For dose-response characterization, we applied benchmark-dose modeling to human data and determined a point of departure (the 95% lower confidence limit for 5% inhibition of iodide uptake) of 0.

Development of a chronic inhalation reference level for respirable crystalline silica.

Chronic inhalation exposure of workers to crystalline silica can result in silicosis. The general public can also be exposed to lower levels of crystalline silica from quarries, sand blasting, and entrained fines particles from surface soil. We have derived an inhalation chronic reference exposure level for silica, a level below which no adverse effects due to prolonged exposure would be expected in the general public.

Development of acute inhalation reference exposure levels (RELs) to protect the public from predictable excursions of airborne toxicants.

Uniform guidelines have been developed for the derivation of 1-h acute inhalation reference exposure levels (RELs) applicable to the general public exposed routinely to hazardous substances released into the environment. Existing acute exposure guidance values developed by other organizations have been examined, and strengths and weaknesses in these existing guidelines have been identified. The results of that examination have led to the development of a reproducible and resource-intensive methodology to calculate acute inhalation RELs for 41 prioritized chemicals.

Characterization of the LOAEL-to-NOAEL uncertainty factor for mild adverse effects from acute inhalation exposures.

This analysis was undertaken to reduce uncertainty in acute inhalation risk assessment for mild acute effects. Applying uncertainty factors (UFs) to the no-observed-adverse-effect level (NOAEL) is the primary approach used in threshold-based risk assessments. When a NOAEL is unavailable, a UF of 10 is often applied to a lowest-observed-adverse-effect level (LOAEL) to estimate the NOAEL.