Risk assessment of methylmercury based on internal exposure and fish and seafood consumption estimates in Taiwanese children.

Fish and seafood consumption is a major source of human exposure to methylmercury (MeHg). This study evaluated the potential health risk of MeHg in Taiwanese children from fish and seafood consumption using a toxicokinetic model, hazard quotients and hazard indices (HIs). Two biomonitoring programs provided an important resource for blood specimens for assessing MeHg exposure in human populations. For internal exposures, total mercury (THg) was measured as a biomarker of MeHg in whole blood (WB) and red blood cells using inductively coupled plasma mass spectrometry and cold-vapor atomic absorption spectroscopy, respectively. The THg concentrations were used to estimate MeHg concentrations. Consumption of fish and seafood was assessed using the National Food Consumption database in Taiwan, while mercury concentrations in edible fish and seafood were collected from published studies in Taiwan. Our results indicated that 1) the highest median THg (representing estimated MeHg) daily intakes were found to decrease with increasing age in children consuming saltwater fish for age groups 0-3, 4-6, 7-12, and 13-18 years: 0.03 > 0.02 > 0.017 > 0.007 (µg kg-BW-1 day-1); 2) HI greater than one, based on WB-THg, was found in 28% of 4-6-year-old children and 3) internal exposure estimates based on WB-THg, though slightly higher, were comparable to those based on fish and seafood consumption. The results support the use of dietary intake estimates as surrogates for internal blood MeHg levels in Taiwanese children to assess their exposure.

Nanotechnology and nanomaterials: toxicology, risk assessment, and regulations.

Nanomaterials have very unique chemical and physical properties that suggest potential health hazards, but limited health and safety information exists for engineered nanomaterials. This review identifies a need for expanding efforts for addressing health and safety concerns in nanotechnology development and in nanotoxicology of engineered nanomaterials. The efforts include research to generate data for safety evaluation, toxicologic evaluation of potential human health effects, risk assessment to support risk-management decision-making, and regulations development to protect human health and the environment. The federal government's current understanding is that existing statutory authorities are adequate to address oversight of nanotechnology and its applications. On the other hand, the present review identifies weaknesses in the current research efforts and inadequacies in existing regulations. A collaborative effort involving multidisciplinary groups is a key element to address the related needs and issues. While federal agencies with regulatory responsibilities are looked upon to develop and implement sound policies and regulations to protect public health and the environment, state agencies may be required to initiate policies which rapidly incorporate new innovations and address public concerns. To address current and futures need related to nanotechnology, the responsible state agencies need to fill the information gaps and address the health and environmental issues. In California, activities have been initiated, but legislative authority and resources are required to provide risk assessment and health protection in an efficient and timely manner.

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 0.0037 mg/kg/day. A PHG of 6 ppb was calculated by using an uncertainty factor of 10, a relative source contribution of 60%, and exposure assumptions specific to pregnant women. The California Department of Health Services will use the PHG, together with other considerations such as economic impact and engineering feasibility, to develop a California maximum contaminant level for perchlorate. We consider the PHG to be adequately protective of sensitive subpopulations, including pregnant women, their fetuses, infants, and people with hypothyroidism.

Hot topics in toxicology.

Toxicology is facing new challenges in addressing issues that will have an impact on developing and meeting new regulatory guidance, public health protection and research directions. Efforts are made to define the exposures to potential toxicants, assess the associated risks, and reduce the uncertainties. This discussion presents an overview of the associated regulatory mandates, how various programs are approaching the current issues and the progress made, particularly here in California and also globally. It includes children sensitivity, differences between adults and children, exposure to pesticides, health effects and exposure endpoint measurement, and assessment to chemicals found in drinking water. Furthermore, it addresses issues associated with defining occupational exposure, community exposure and health risk, public perception of hazard, and the role of diet or nutrition in the overall toxicology and health considerations.