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PROTECTING OUR CHILDREN FROM HARM: MEASURING ENVIRONMENTAL RISKS TO CHILDREN REQUIRES UNDERSTANDING THEIR UNIQUE MEANS OF EXPOSURE
Citation:
CohenHubal, E A. PROTECTING OUR CHILDREN FROM HARM: MEASURING ENVIRONMENTAL RISKS TO CHILDREN REQUIRES UNDERSTANDING THEIR UNIQUE MEANS OF EXPOSURE. CHEMICAL AND ENGINEERING NEWS SPECIAL ISSUE 79(13):3, (2001).
Impact/Purpose:
1. To identify those pesticides, pathways, and activities that represent the highest potential exposures to children;
2. To determine the factors that influence pesticide exposures to children;
3. To develop methods for measuring multimedia exposures to children, including methods that account for important activities that take place in home, school, and day care settings;
4. To generate data on multimedia pesticide concentrations, pesticide biomarkers, and exposure factors that can be used as inputs to aggregate exposure models for children.
Description:
Children's exposures to consumer products and environmental contaminants are expected to be different and, in some cases, much higher than adult's exposures. The objectives of our children's exposure research at the National Exposure Research Laboratory are to make use of existing information in developing improved exposure assessment methods and models for children; and to design and conduct research on exposure that will answer questions about age-related differences and will lead to better exposure assessments for children.
For this purpose, exposure is defined as the contact of an individual (at visible external boundaries) with a pollutant for specific durations of time. Exposure assessments are developed to characterize "real-life" situations, whereby: a) potentially exposed populations are identified, b) potential pathways of exposure are identified, and c) the magnitude, frequency, duration and time-pattern of contact with a chemical (potential doses) are quantified.
Assessing exposures to consumer products and environmental contaminants in a non-occupational setting poses some significant challenges. Understanding dermal and non-dietary exposures to infants and young children is particularly difficult for several reasons.
Infants and young children are experiencing rapid physiological and behavioral development. These developmental stages will impact both a child's susceptibility to toxic effects as well as the potential for exposure. An understanding of physiological and behavioral characteristics as a function of the age and developmental stage of a child is critical for categorizing children and collecting data on their exposures.
Children behave very differently than adults. Children's behavior and the way that children interact with their environment may have a profound effect on the magnitude of their chemical exposures. Children crawl, roll, and climb over contaminated surfaces, resulting in higher dermal contact than would be experienced by adults in the same environment. Increased dietary ingestion of contaminants occurs when children handle and eat foods that have come in contact with the floor or other contaminated surfaces. Children's mouthing activities (hand-to-mouth and object-to-mouth) will result in non-dietary ingestion of chemicals if the hands or objects are contaminated. An improved understanding of the behaviors that lead to exposures as well as the inter and intra-individual variability associated with these behaviors is needed.
It is difficult to develop and verify exposure factors for infants and young children. Controlled laboratory studies in which children are intentionally exposed to contaminants are inappropriate. Using adult surrogates for these studies introduces bias, because adults cannot mimic the contact activities of children. Developing an accurate record an infant's activity patterns also poses a challenge. Direct observation (including videotaping) is considered the most accurate way to record an infant's activities, especially as they relate to dermal exposure. However, this methodology is very labor intensive and costly. Before detailed activity data can be effectively collected and evaluated, knowledge is required on important activities and contact parameters.
It is also difficult to monitor children's exposures in the field. Current techniques for measuring dermal exposure are limited in utility. Measures of skin contamination do not reflect changes in dermal loading that occur subsequent to sampling and do not indicate the amount of contamination actually absorbed through the skin. In addition, dermal measurement methods developed for occupational use (where the environment and physical activities may be relatively homogenous) may not be useful for measuring children's residential exposures. There are also significant challenges associated with collecting and interpreting biomarker data (e.g., urine) from children, making it difficult to verify exposure factors and assessment approaches for infants and young children.
Currently, the data on children's exposures and activities are insufficient to adequately assess residential exposures to consumer products and environmental contaminants. To improve this database, several general areas of research are required. Appropriate age/developmental benchmarks for categorizing children in exposure assessments must be identified. To do this, a better understanding is required of the relationship between behavioral and biological development as well as the importance of each in creating critical windows of susceptibility. The activity pattern data for children (especially young children) required to assess exposure by all routes need to be developed. Methods for monitoring children's exposures need to be developed and improved. Finally, population based field studies are needed to monitor for compounds of concern in residential media and for the associated biomarkers in children's blood and urine.
Researchers in government, academia, and industry have begun to address all of these issues. Collaborative efforts among these groups promise to quickly move the state of exposure science forward. As a result, over the next five to ten years, expect to see improved methods and approaches for conducting exposure assessments, development of the databases required to conduct these assessment, and significant reduction in the uncertainty associated with exposure assessments for children.
This work has been funded wholly or in part by the United States Environmental Protection Agency. It has been subjected to Agency review and approved for publication.