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K Sexton

Publications and source records attributed to K Sexton.

50 records · Page 3Linked to original sources
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Assessing children's exposure to hazardous environmental chemicals: an overview of selected research challenges and complexities.

There is renewed interest in the United States regarding characterization of children's exposures to hazardous environmental chemicals. Many studies are currently underway that use novel and innovative approaches to assess childhood exposures to a variety of toxic chemicals, including both persistent and nonpersistent compounds. This article reviews some of the critical challenges that can impede scientifically rigorous studies designed to measure children's environmental exposures. The discussion briefly examines three topical areas: administrative issues (IRB approval, participant incentives, community involvement, and communication of results to research participants and stakeholders); data-collection issues (identifying and recruiting children/families, measuring actual exposures/doses); and issues related to chemical analysis of biological samples (examples of chemicals and chemical classes that can be measured in human tissue and excreta, effects of a child's age on the type and amount of biological samples available for analysis). These research complexities are discussed in the context of developing more effective and efficient exposure assessment methods.

Child↗
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Quantitative analysis of children's microactivity patterns: The Minnesota Children's Pesticide Exposure Study.

The National Human Exposure Assessment Survey (NHEXAS)/Minnesota Children's Pesticide Exposure Study (MNCPES) was a population-based study designed to characterize children's exposure to residential pesticides and to evaluate the contribution of residential and children's activities to children's exposure. Families of 168 children were surveyed for residential use of pesticides and children's activities. From these homes, families of 102 children between the ages of 3 and 13 years participated in a week-long intensive exposure study. Of the 102 children, 19 children were videotaped for four consecutive hours in their normal daily activities. The survey responses indicated that the youngest children were more likely to exhibit behaviors that would foster exposure to environmental contaminants. Comparison of questionnaire responses indicated that the videotaped subsample was representative of the exposure study population. The microactivities of the videotaped children that might contribute to their exposure via ingestion or dermal routes were quantified. Hand-to-mouth and object-to-mouth activities were observed most frequently among the youngest children. The youngest children were also most likely to be barefoot both indoors and outside. Gender differences were found in mouthing behavior and the proportion of observed time spent outdoors.

Activities of Daily Living↗
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Estimating human exposures to environmental pollutants: availability and utility of existing databases.

Information about human exposures to environmental agents is a crucial component of informed decisions about protection of public health. Results from an inventory of exposure-related databases are used to examine the value of exposure information for risk assessment, risk management, surveillance of status and trends, and epidemiologic studies. Findings indicate that current and future exposure-related databases should include (1) standardized procedures for the collection, storage, analysis, and reporting of data; (2) an enhanced ability to compare data over time, i.e., conduct comparison studies of "old" and "new" methods; (3) mechanisms for coordination and cooperation among public and private-sector organizations with respect to the design, maintenance, exchange, and review of information systems; (4) measurements of actual exposures and dose for relevant human populations; and (5) data collection, storage, and retrieval methods that permit easy manipulation of information for both model building and testing.

Data Collection↗
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"Environmental justice": the central role of research in establishing a credible scientific foundation for informed decision making.

Although much of the evidence is anecdotal and circumstantial, there are mounting concerns that environmental health risks are borne disproportionately by members of the population who are poor and nonwhite. We examine the central role of environmental health research in defining the dimensions of the problem, understanding its causes, and identifying solutions. Environmental health sciences, including epidemiology, exposure analysis. pharmacokinetics, toxicology, and surveillance monitoring, must be employed to determine the extent to which society has achieved "equity" and "justice" in safeguarding the health and safety of its citizens. By improving our ability to identify, evaluate, prevent, and/or reduce risks for all members of society, environmental health research can contribute directly to fair and equitable protection for everyone, regardless of age, ethnicity, gender, race, or socioeconomic status.

Decision Making↗
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Air pollution health risks: do class and race matter?

Air pollution is not spread evenly across demographic groups. Exposures and associated health risks appear to fall disproportionately on populations that are poor and nonwhite. Although scientific evidence documenting disparities in air pollution exposures, doses, and health effects is scant, the available data strongly support the contention that disadvantaged groups, many of whom are ethnic and racial minorities, routinely encounter levels of air pollution that are higher than average. The extent to which exposure differentials contribute to observed differences in health status by class and race is unknown, but worthy of further investigation. We recommend several steps, all of them feasible and most of them relatively inexpensive, to improve our understanding and ability to address environmental health disparities.

Air Pollution↗
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Neutralization of beta-lactam antibiotics in an environmental monitoring medium.

The neutralizing ability of Difco Bacto Penase, BBL Penicillinase, and Genzyme beta-lactamase for penicillin G, oxacillin, cephalothin, cefazolin, ceftazidime, ceftriaxone, cefotaxime, imipenem, and meropenem was determined in an agar medium. Trypticase soy agar plates (20 mL) containing 200 MU/L Difco Penase, 200 MU/L BBL Penicillinase, or 2 vials/L of Genzyme beta-lactamase were dosed with 20, 50, and 100 micrograms of each antibiotic and then inoculated (50-100 CFU/plate) with a susceptible microorganism. Percentage recoveries of the organism were calculated after incubation. Genzyme beta-lactamase effectively neutralized 100 micrograms of all the antibiotics except ceftazidime (32% recovery with 20 micrograms). The two penicillinases effectively neutralized 100 micrograms of penicillin G, oxacillin, cephalothin, and cefazolin; were slightly effective against ceftriaxone and cefotaxime (20-57% recovery with 20 micrograms); and totally ineffective against ceftazidime, imipenem, and meropenem. This investigation resulted in a useful procedure for qualifying and/or selecting a beta-lactamase for use in environmental monitoring medium to neutralize a particular beta-lactam.

Anti-Bacterial Agents↗
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An inventory of human exposure-related data bases.

An inventory of Federally-sponsored data bases, which either have been or could be used to estimate human exposures to environmental agents, was compiled through a joint effort by the Environmental Protection Agency (EPA), the National Center for Health Statistics (CDC-NCHS), and the Agency for Toxic Substances and Disease Registry (ATSDR). The inventory includes sixty-seven exposure-related data systems that meet the following criteria: cover a relatively large geographical area (e.g., national, state); provide reasonable access to information; and are supported, at least in part, by Federal funds. Findings allow for comparison of data bases according to 1) exposure estimators (e.g., emission estimates, environmental measurements), 2) sample types (e.g., air, water soil, food, human tissue), 3) measured/observed parameters (e.g., pesticides, PCBs, microorganisms), 4) geographic scope (e.g., national, regional, state), 5) sample collection frequency (e.g., yearly, quarterly, daily), and 6) sample location identifiers (e.g., latitude/longitude, zip code, county). Results indicate that existing data bases were established for a variety of reasons (e.g., regulatory compliance, research, monitor environmental conditions, legal requirements) and contain information which varies widely in terms of quality, relevance, and availability. Although the inventory identifies many potential sources of information, it also highlights significant shortcomings in the available systems, including an almost complete absence of data on contact between people and environmental agents (human exposure) and on the amount of the agent that is absorbed into the body (dose).

Data Collection↗
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Informed decisions about protecting and promoting public health: rationale for a National Human Exposure Assessment Survey.

Accurate and reliable exposure-related information is essential for informed decisions about protecting and promoting public health. The need for more and better data on population exposures to environmental chemicals is discussed, with emphasis on the justification for collecting baseline data on exposure distributions for the general population and for important population subgroups. A rationale is provided for undertaking exposure surveillance in the U.S. population by means of a National Human Exposure Assessment Survey (NHEXAS). The knowledge and understanding generated by NHEXAS will contribute to more informed and more credible decisions in three ways: (1) by establishing a core set of approaches, methods, and data that will significantly advance the field of exposure analysis; (2) by developing a strong and direct connection between science (exposure research and surveillance) and policy (decisions about assessment, management, and communication of health risks); and (3) by creating a connected group of researchers and regulators who share a mutual appreciation and understanding of the value of exposure surveillance for well-reasoned decisions.

Decision Trees↗
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Overview of important design issues for a National Human Exposure Assessment Survey.

Exposure issues have important consequences for regulatory decisions. Reliable answers to exposure questions are critical for site cleanup, model validation, and cumulative risk issues, as well as giving perspective on our risk estimates. This paper discusses some of the important issues in designing the National Human Exposure Assessment Survey (NHEXAS) and, by implication, other exposure-monitoring-based studies as well. Sampling design issues are discussed in terms useful to exposure assessors. These issues include simple random sample designs versus more complex multistage designs, design efficiency, how to determine the sample size for the desired precision of the estimate, and the effects of stratification and oversampling on the needed sample size. This paper also discusses several important nonsampling issues such as population definition, response rates, and several potential sources of error in interpreting the monitoring results.

Data Collection↗
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Integrating science and policy in a National Human Exposure Assessment Survey.

Despite tremendous progress in environmental protection over the past two decades, critical gaps remain in our understanding of actual human exposures to environmental chemicals. While the research community and the policy makers share the common goal of reducing environmental risks, it must be recognized that their information needs are often divergent. The design of effective exposure research must consider the needs and practical limitations of regulators and policy-makers and balance the often conflicting needs of policy and science. This paper examines some of the inherent conflicts between exposure research (science) and regulatory (policy) realities, and describes how the needs of policy makers were integrated into the design of a National Human Exposure Assessment Survey (NHEXAS). NHEXAS represents perhaps the most ambitious exposure surveillance effort ever undertaken. Exposure surveillance is presented as a model for bridging the gap between policy and science in the development of risk management approaches. The success of risk-based priority setting will depend upon the quality of information to support the risk assessment process. Environmental exposure surveillance will be essential to the characterization of risks and, ultimately, to the evaluation of the effectiveness of regulatory strategies.

Decision Support Techniques↗
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Improving exposure assessment by monitoring human tissues for toxic chemicals.

Typically, the availability of appropriate data to estimate human exposures to toxic chemicals is scarce. Consequently, exposure assessments are often based on indirect surrogates of exposure, such as a combination of questionnaire data on time-activities and concentrations of toxic chemicals measured in environmental media (e.g., air, water, food, soil, dust). Recent advances, however, make it technically feasible and relatively affordable to measure low levels of multiple toxic chemicals in accessible human tissues (e.g., blood, urine). The increasing availability of biological markers for exposure, along with improvements in pharmacokinetic understanding, present new opportunities to estimate exposure from human tissue measurements and from knowledge of intake and uptake parameters. Biological monitoring provides exposure information that is usually complementary to the type of exposure information obtained from environmental monitoring. Biological and environmental monitoring can be used separately or together in order to meet desired objectives. We present here a discussion of the value of biological monitoring for improving exposure assessment. We emphasize the role of biological monitoring in identifying high-priority exposures, evaluating the effectiveness of intervention and prevention efforts, identifying at-risk subpopulations, recognizing time trends in population exposures, establishing reference ranges of tissue concentrations, and providing integrated dose measurements.

Environmental Monitoring↗