Scientific advances provide opportunities to improve pediatric environmental health

Abstract

The health consequences of contaminants in the environment, with respect to the health of children and infants, recently have been dramatically brought to public attention by the motion pictures Erin Brockovich and A Civil Action. These productions focused public attention on the potential link between water contaminants and pediatric health, a continuing subject of public concern. As a consequence of the increasing production of new commercial chemicals, many chemicals have appeared in the scientific and public awareness as potential threats to health. These new or novel compounds eventually distribute in the environment and often are termed emerging contaminants. Gitterman and Bearer stated, “Children may serve as unwitting sentinels for society; they are often the youngest exposed to many environmental toxicants and may become the youngest in age to manifest adverse responses.”1.Gitterman B.A. Bearer C.F. A developmental approach to pediatric environmental health.Pediatr Clin North Am. 2001; 48: 1071-1083Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar The discipline of pediatric environmental health is still in its adolescence,2.Landrigan P.J. Children's environmental health: lessons from the past and prospects for the future.Pediatr Clin North Am. 2001; 48: 1319-1330Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar but it will be increasingly important as new chemicals are generated and as more is learned about the health effects of chemicals already in commerce. Here, we provide an overview of recent advances in biomonitoring and environmental monitoring of environmental contaminants including emerging contaminants. Our purpose in writing this commentary is to make pediatricians aware of the current resources available for learning about pediatric environmental health and of ongoing research initiatives that provide opportunities to improve pediatric environmental health.1. BiomonitoringThe most extensive overview to date of the nation's exposure to environmental contaminants was recently released by the Centers for Disease Control and Prevention (CDC) (available online at: http://www.cdc.gov/exposurereport).3.Centers for Disease Control and Prevention Second National Report on Human Exposure to Environmental Chemicals. Department of Health and Human Services, Atlanta (GA)2003http://www.cdc.gov/exposurereportGoogle Scholar The CDC reported biomarkers of exposure (ie, concentrations of a chemical or its metabolite) for 116 chemicals in blood and/or urine samples, collected from people as young as aged 1 year, across the United States during the 2-year period of 1999 to 2000. Samples were from selected participants in the National Health and Nutrition Examination Survey. This survey was designed to include a representative sample of people so that the typical exposure levels of the civilian, noninstitutionalized US population could be characterized. The report results can be used in several ways: (1) trends in changing exposure levels can be tracked, revealing whether efforts to reduce exposures are really working; (2) the number of people with elevated levels of chemicals with known toxicity can be identified; (3) human health effect research priorities can be set based on the study results; and (4) people with high exposures compared with typical exposure levels can be identified.3.Centers for Disease Control and Prevention Second National Report on Human Exposure to Environmental Chemicals. Department of Health and Human Services, Atlanta (GA)2003http://www.cdc.gov/exposurereportGoogle Scholar It is important to recognize that the presence of a chemical in the blood or urine does not necessarily mean a person is at risk for adverse health effects. For many contaminants in the report, no health effect standards or environmental safety levels have been established, but currently the health effects of many of these contaminants are being studied to determine safe and unsafe levels.4.Hileman B. Environmental chemicals. CDC releases most extensive assessment to date of human exposure.C&EN. 2003; 81: 33-36Google ScholarOnly a fraction of the contaminants present in the environment were included in the CDC study. Chemicals were included for many reasons such as the seriousness of health effects known or suspected to result from some level of exposure. A key consideration for the inclusion of chemicals in the biomonitoring study was the availability of adequate biomonitoring methods that had a feasible cost. Future CDC surveys will include additional contaminants such as speciated arsenic and speciated mercury.4.Hileman B. Environmental chemicals. CDC releases most extensive assessment to date of human exposure.C&EN. 2003; 81: 33-36Google ScholarIn the CDC study, for most chemicals only urine biomonitoring data were available, and results were reported only for people older than aged 12 years; but more information was included for several chemicals, including lead. The geometric mean blood lead concentrations for children and adolescents aged 1 to 5 years, 6 to 11 years, and 12 to 19 years were 2.23, 1.51, and 1.10 μg/dL, respectively, illustrating that typically younger children have higher blood lead levels than older children. The CDC recommend that children's blood lead levels not exceed 10 μg/dL, and only 16 of the 723 children aged 1 to 5 years in the study exceeded that guideline. The geometric mean of the creatinine-adjusted urine concentrations were frequently higher for children aged 6 to 11 years than for adolescents aged 12 to 19 years (eg, for metals such as antimony and thallium and phthalates such as mono-butyl phthalates and mono-benzyl phthalates).Higher contaminant concentrations in the blood and urine of children, in comparison with those of adolescents or adults, are not unexpected. Children and babies can be exposed to higher internal doses than adults because they eat much more food per body weight, potentially contaminated with emerging contaminants, than do adults. Differences in patterns of behavior also can result in higher internal doses for infants (eg, from crawling around on the ground) and for children (eg, from playing in the mud). Higher internal doses could translate to a greater risk for this sensitive population. Clearly, it is important to include children in biomonitoring studies to quantify their exposure levels to environmental contaminants.As an example of the importance of biomonitoring, consider the issue of breast milk. Many studies have demonstrated that breast milk can be a source of chemical exposure for babies, eg, for persistent pesticides, industrial chemicals and metals,5.Jensen A.A. Chemical contaminants in human-milk.Residue Rev. 1983; 89: 1-128PubMed Google Scholar and polychlorinated biphenyls.6.Jacobson J.L. Jacobson S.W. Intellectual impairment in children exposed to polychlorinated biphenyls in utero.N Engl J Med. 1996; 335: 783-789Crossref PubMed Scopus (969) Google Scholar Research is ongoing on the health risks associated with chemical exposure from breast feeding. Van Oostdam et al provided the following guidance based on their study of persistent bioaccumulative toxic chemicals in a Michigan fish consumers study7.Van Oostdam J. Gilman A. Dewailly E. et al.Human health implications of environmental contaminants in Arctic Canada: a review.Sci Total Environ. 1999; 230: 1-82Crossref PubMed Scopus (227) Google Scholar:“There are many recognized advantages to breast-feeding to infants and to mothers, including improved nutrition, increased resistance to infection, protection against allergies, better parent-child relationships….With full regard for the uncertainty over the toxic effects of organochlorines in human milk, the known benefits of breast-feeding are extensive and serve as a strong rationale for advising mothers to continue to breast-feed their newborns unless cautioned by their local health care worker to reduce or stop.”Only mothers exposed to significantly elevated levels of contaminants known to cause adverse health for the infant should consider using formula. Getting an appropriate patient history may help identify those children at risk from contaminants in breast milk. Additionally, biomonitoring and environmental monitoring studies can help identify the specific regions or locations where mothers may be at risk. Recently, at the Technical Workshop on Human Milk Surveillance and Research on Environmental Chemicals in the United States, the prioritization of chemicals included in human milk research and/or surveillance was suggested to reflect chemicals that are persistent in the environment, that women may be exposed to at high levels, that are known or suspected to have toxic effects, that are of historical interest for identifying trends, that women are exposed to in medicine or occupationally, and that are of emerging concern.8.Berlin C.M. Kacew S. Lawrence R. LaKink J.S. Campbell R. Criteria for chemical selection for programs on human milk surveillance and research for environmental chemicals.J Toxicol Environ Health A. 2002; 65: 1839-1851Crossref PubMed Scopus (33) Google Scholar2. Environmental monitoringAdvances in instrumentation, methods of isolation, purification, and determination in contaminant analytical chemistry are providing scientists with increasing amounts of information on the number and levels of emerging contaminants that are present in our environment. Recently, the US Geological Survey (USGS), Water Resources Discipline, published the first nationwide study of the concentration and distribution of emerging contaminants in water resources (available online at http://toxics.usgs.gov/pubs/OFR-02-94/index.html).9.Koplin D.W. Furlong E.T. Meyer M.T. et al.Pharmaceuticals, hormones, and other organic wastewater contaminants in U.S. Streams, 1999-2000: a national reconnaissance.Environ Sci Technol. 2002; 36: 1202-1211Crossref PubMed Scopus (6627) Google Scholar Several types of chemicals were included as emerging contaminants. Some are common, and others are unfamiliar but widely used in commerce. Chemicals in the USGS study included: pesticides, prescription and nonprescription drugs, veterinary pharmaceuticals, steroids, reproductive hormones, personal care products, biogenic hormones, industrial byproducts, products of oil use and combustion, and other extensively used chemicals.In 1999 and 2000, concentrations of 82 emerging contaminants in water samples from 139 streams in 30 states were determined using 5 newly developed analytical methods.9.Koplin D.W. Furlong E.T. Meyer M.T. et al.Pharmaceuticals, hormones, and other organic wastewater contaminants in U.S. Streams, 1999-2000: a national reconnaissance.Environ Sci Technol. 2002; 36: 1202-1211Crossref PubMed Scopus (6627) Google Scholar Sampling sites were biased to reflect streams affected by intense urbanization or livestock production. The USGS study found that the most frequently detected compounds in these highly affected streams were associated with commercial products from residential, industrial, or agricultural use: coprostanol (fecal steroid), cholesterol (plant and animal steroid), N,N-diethyltoluamide (insect repellant), caffeine (stimulant), and triclosan (antimicrobial disinfectant). Although multiple emerging contaminants were detected in the majority of samples, with a median of 7 and as many as 38 emerging contaminants being detected in a single sample, only 5% of the measured emerging contaminant concentrations in sampled stream waters were greater than 1 μg/L.The results of the USGS study can be used to identify candidate chemicals to include in future biomonitoring studies. Recognition of potential water contamination by emerging contaminants has prompted federal agencies to issue advice about the disposal of drugs and household products (eg, see online: http://www.epa.gov/nerlesd1/chemistry/pharma/faq.htm). Results of the USGS study are significant for pediatric environmental health because these data demonstrate for the first time the widespread presence of emerging contaminants in the environment and thus the potential of exposure pathways to children.3. New scientific initiativesThe issue of the effects of the environment on pediatric health is complex, but there have been many recent scientific advances on this topic. The National Institute of Environmental Health Sciences (NIEHS) and the United States Environmental Protection Agency (US EPA) have jointly funded 12 Centers for Children's Environmental Health (for additional information, online see: http://www.niehs.nih.gov/translat/children/children.htm). The goals of this program are to conduct research to reduce hazardous exposures and their adverse health effects; to develop strategies for the measurement of children's exposures to chemicals of concern; to decrease the prevalence, morbidity, and mortality of pediatric environmental disease; to disseminate research findings to the public health community; and to increase the training of pediatricians so that they can recognize and treat environmentally induced diseases.10.Centers for Children's Environmental Health and Disease Prevention Research. National Institute of Environmental Health Sciences and the United States Environmental Protection Agency, Bethesda (MD)January 18, 2003Google ScholarThe NIEHS and the US EPA have focused on five disease areas for research. The first area encompasses asthma and other respiratory diseases. Research currently funded includes studies on the effectiveness of specific interventions at reducing and preventing asthma and studies on genetic susceptibility to asthma. In the second research area, birth defects and the fetal basis of adult disease, the observation that genotype does not necessarily dictate phenotype, has garnered much interest in exploring gene-environment interactions and the role of these interactions in causing birth defects. Third, research has been focused on the relationship between environmental contaminants and learning behavioral and developmental disorders. Chemicals known to cause neurological impairments include lead, methylmercury, and polychlorinated biphenyls. Although the gross toxicological effects of these compounds have been studied, the possibility of subtle effects (eg, whether exposure to low levels plays a role in causing attention deficit hyperactivity disorder) is being examined. For the fourth research area, childhood cancer, in one research initiative researchers are attempting to link specific chemical exposures with genetic changes in childhood leukemia. The fifth research area targets endocrine disruptors, which are chemicals that can interfere with hormonal systems critical in the development of the brain, the immune system, and the reproductive system. Infants and children may have enhanced risk from low-level exposures to these compounds because of the importance of the endocrine system in development. The NIEHS and the CDC are collaborating in a project attempting to quantify 70 compounds thought to be endocrine disruptors in blood samples collected during the National Health and Nutrition Examination Survey. Additional information on this research program can be found online (http://www.niehs.nih.gov/oc/factsheets/ceh/home.htm).An additional benefit has been attained through the experiences of the Children's Environmental Health Research Centers. Based on the belief that it is essential not only to identify risk factors but also to reduce exposures and to translate advances in science into policy and medical practice, the use of the innovative community-based participatory research (CBPR) project has been encouraged. In CBPR, scientists work with the community in all aspects of the research process in a partnership. The CBPR facilitates collaboration and helps build trust between the community and the scientist while making available community resources to the scientist and providing additional focus to the research. This aids in the dissemination of research findings and helps the community relay environmental health concerns to policy makers. Additionally, it provides the researchers with a partnership for developing interventions that work. Collaboration between people with different backgrounds and different ideas can contribute valuable new ideas to the field of pediatric environmental health.4. Resources for pediatriciansTypically, pediatricians do not have special training in environmental health, but they need to be informed when faced with a patient whose parents are concerned. The pediatrician can play a critical role in the prevention of environmentally induced disease by educating parents and patients, taking into consideration the fact that prevention must be approached differently for patients of varying ages.1.Gitterman B.A. Bearer C.F. A developmental approach to pediatric environmental health.Pediatr Clin North Am. 2001; 48: 1071-1083Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar Often parents visit the doctor with concerns about their child's environmental exposures, but the child exhibits no clinical signs or symptoms. Some of these patients may have nothing to be concerned about, but others may be experiencing subclinical toxicity. Although high doses of environmental toxicants typically cause obvious adverse health effects, lower doses can exhibit subtle effects that may or may not be detected with special testing. For example, there has been a historical decline in the level of lead exposure deemed to be safe because it took many years to identify subtle effects associated with lower-level exposures.11.American Academy of Pediatrics Committee on Environmental Health Etzel R.A. Balk S.J. Pediatric environmental health. 2nd ed. American Academy of Pediatrics, Elk Grove Village (IL)2003Google Scholar In one study on the long-term effects of lead exposure, children exposed to low levels of lead (ie, children with dentin lead levels >20 ppm) and demonstrating no obvious signs of lead toxicity had a markedly increased risk of dropping out of high school and of having reading disabilities years later.12.Needleman H.L. Schell A. Bellinger D. Leviton A. Allred E.N. The long-term effects of exposure to low doses of lead in childhood: an 11-year follow-up report.N Engl J Med. 1990; 322: 83-88Crossref PubMed Scopus (951) Google Scholar The issues involved in environmentally related illness are complex, and pediatricians need to know what types of chemicals present in a child's environment could make them sick so that they know what questions to ask, eg, asking about a parent's occupation or a child's hobbies could provide critical information.There are many resources from which pediatricians can draw. The recently revised second edition of the American Academy of Pediatrics book Pediatric Environmental Health, a practical compilation of clinically relevant pediatric health issues, covers topics ranging from specific chemical and physical hazards (eg, environmental chemicals, air pollutants, and radiation) to communicating about environmental health.11.American Academy of Pediatrics Committee on Environmental Health Etzel R.A. Balk S.J. Pediatric environmental health. 2nd ed. American Academy of Pediatrics, Elk Grove Village (IL)2003Google Scholar The recently published monograph “Child health and the environment” has themes such as the susceptibility of the developing fetus and infant to toxicants, the effects of modifying factors such as poverty and nutrition, and the importance of timely intervention.13.Wigle D.T. Child health and the environment. Oxford University Press, New York2003Google Scholar For general information about pediatric environmental health issues such as the health effects of lead and asthma and allergy prevention, NIEHS pamphlets are available online (http://www.niehs.nih.gov/oc/factsheets/fsmenu.htm).The Agency for Toxic Substances and Disease Registry (ATSDR) together with the American Academy of Pediatrics Committee on Environmental Health sponsored an initiative for the environmental safety of children and held a workshop called the Environmental Safety Net for Children to educate local pediatricians and public health representatives in the promotion of pediatric environmental health.14.Balk S.J. Shea K.M. A partnership to establish an environmental safety net for children.Pediatrics. 2003; 112: 209-264Google Scholar Additionally, the ATSDR has posted online the document, “Case studies in environmental medicine, pediatric environmental health” (http://www.atsdr.cdc.gov/HEC/CSEM/pediatric/principles.html).For sick children for whom environmental factors may be important, there are other resources besides the pediatrician, clinical toxicologist, and poison centers. Currently, 10 Pediatric Environmental Health Specialty Units in the United States are funded by the ATSDR and the US EPA in collaboration with the Association of Occupational and Environmental Clinics. These Pediatric Environmental Health Specialty Units, staffed by pediatricians who specialize in environmental medicine, occupational medicine physicians, and other specialists, are designed to be a resource for community pediatricians (for more information, online see: http://www.atsdr.cdc.gov/HEC/natorg/pehsu.html).15.Balk S.J. Resources for pediatricians: how do I answer questions from parents, patients, teachers, and others?.Pediatr Clin North Am. 2001; 48: 1099-1111Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar5. SummaryThe field of pediatric environmental health is changing and will continue to change rapidly as emerging chemical threats to children are identified, as further advances in biomonitoring and environmental monitoring are achieved, and as research programs of the NIEHS and the US EPA bear fruit. Besides the obvious responsibility of pediatric practitioners to stay abreast of recent developments, pediatricians can play an important role in guiding future areas of research. Through multidisciplinary interactions and participation in CBPR and workshops, pediatricians can take advantage of the opportunities provided by scientific advances to improve pediatric environmental health. The health consequences of contaminants in the environment, with respect to the health of children and infants, recently have been dramatically brought to public attention by the motion pictures Erin Brockovich and A Civil Action. These productions focused public attention on the potential link between water contaminants and pediatric health, a continuing subject of public concern. As a consequence of the increasing production of new commercial chemicals, many chemicals have appeared in the scientific and public awareness as potential threats to health. These new or novel compounds eventually distribute in the environment and often are termed emerging contaminants. Gitterman and Bearer stated, “Children may serve as unwitting sentinels for society; they are often the youngest exposed to many environmental toxicants and may become the youngest in age to manifest adverse responses.”1.Gitterman B.A. Bearer C.F. A developmental approach to pediatric environmental health.Pediatr Clin North Am. 2001; 48: 1071-1083Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar The discipline of pediatric environmental health is still in its adolescence,2.Landrigan P.J. Children's environmental health: lessons from the past and prospects for the future.Pediatr Clin North Am. 2001; 48: 1319-1330Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar but it will be increasingly important as new chemicals are generated and as more is learned about the health effects of chemicals already in commerce. Here, we provide an overview of recent advances in biomonitoring and environmental monitoring of environmental contaminants including emerging contaminants. Our purpose in writing this commentary is to make pediatricians aware of the current resources available for learning about pediatric environmental health and of ongoing research initiatives that provide opportunities to improve pediatric environmental health. 1. BiomonitoringThe most extensive overview to date of the nation's exposure to environmental contaminants was recently released by the Centers for Disease Control and Prevention (CDC) (available online at: http://www.cdc.gov/exposurereport).3.Centers for Disease Control and Prevention Second National Report on Human Exposure to Environmental Chemicals. Department of Health and Human Services, Atlanta (GA)2003http://www.cdc.gov/exposurereportGoogle Scholar The CDC reported biomarkers of exposure (ie, concentrations of a chemical or its metabolite) for 116 chemicals in blood and/or urine samples, collected from people as young as aged 1 year, across the United States during the 2-year period of 1999 to 2000. Samples were from selected participants in the National Health and Nutrition Examination Survey. This survey was designed to include a representative sample of people so that the typical exposure levels of the civilian, noninstitutionalized US population could be characterized. The report results can be used in several ways: (1) trends in changing exposure levels can be tracked, revealing whether efforts to reduce exposures are really working; (2) the number of people with elevated levels of chemicals with known toxicity can be identified; (3) human health effect research priorities can be set based on the study results; and (4) people with high exposures compared with typical exposure levels can be identified.3.Centers for Disease Control and Prevention Second National Report on Human Exposure to Environmental Chemicals. Department of Health and Human Services, Atlanta (GA)2003http://www.cdc.gov/exposurereportGoogle Scholar It is important to recognize that the presence of a chemical in the blood or urine does not necessarily mean a person is at risk for adverse health effects. For many contaminants in the report, no health effect standards or environmental safety levels have been established, but currently the health effects of many of these contaminants are being studied to determine safe and unsafe levels.4.Hileman B. Environmental chemicals. CDC releases most extensive assessment to date of human exposure.C&EN. 2003; 81: 33-36Google ScholarOnly a fraction of the contaminants present in the environment were included in the CDC study. Chemicals were included for many reasons such as the seriousness of health effects known or suspected to result from some level of exposure. A key consideration for the inclusion of chemicals in the biomonitoring study was the availability of adequate biomonitoring methods that had a feasible cost. Future CDC surveys will include additional contaminants such as speciated arsenic and speciated mercury.4.Hileman B. Environmental chemicals. CDC releases most extensive assessment to date of human exposure.C&EN. 2003; 81: 33-36Google ScholarIn the CDC study, for most chemicals only urine biomonitoring data were available, and results were reported only for people older than aged 12 years; but more information was included for several chemicals, including lead. The geometric mean blood lead concentrations for children and adolescents aged 1 to 5 years, 6 to 11 years, and 12 to 19 years were 2.23, 1.51, and 1.10 μg/dL, respectively, illustrating that typically younger children have higher blood lead levels than older children. The CDC recommend that children's blood lead levels not exceed 10 μg/dL, and only 16 of the 723 children aged 1 to 5 years in the study exceeded that guideline. The geometric mean of the creatinine-adjusted urine concentrations were frequently higher for children aged 6 to 11 years than for adolescents aged 12 to 19 years (eg, for metals such as antimony and thallium and phthalates such as mono-butyl phthalates and mono-benzyl phthalates).Higher contaminant concentrations in the blood and urine of children, in comparison with those of adolescents or adults, are not unexpected. Children and babies can be exposed to higher internal doses than adults because they eat much more food per body weight, potentially contaminated with emerging contaminants, than do adults. Differences in patterns of behavior also can result in higher internal doses for infants (eg, from crawling around on the ground) and for children (eg, from playing in the mud). Higher internal doses could translate to a greater risk for this sensitive population. Clearly, it is important to include children in biomonitoring studies to quantify their exposure levels to environmental contaminants.As an example of the importance of biomonitoring, consider the issue of breast milk. Many studies have demonstrated that breast milk can be a source of chemical exposure for babies, eg, for persistent pesticides, industrial chemicals and metals,5.Jensen A.A. Chemical contaminants in human-milk.Residue Rev. 1983; 89: 1-128PubMed Google Scholar and polychlorinated biphenyls.6.Jacobson J.L. Jacobson S.W. Intellectual impairment in children exposed to polychlorinated biphenyls in utero.N Engl J Med. 1996; 335: 783-789Crossref PubMed Scopus (969) Google Scholar Research is ongoing on the health risks associated with chemical exposure from breast feeding. Van Oostdam et al provided the following guidance based on their study of persistent bioaccumulative toxic chemicals in a Michigan fish consumers study7.Van Oostdam J. Gilman A. Dewailly E. et al.Human health implications of environmental contaminants in Arctic Canada: a review.Sci Total Environ. 1999; 230: 1-82Crossref PubMed Scopus (227) Google Scholar:“There are many recognized advantages to breast-feeding to infants and to mothers, including improved nutrition, increased resistance to infection, protection against allergies, better parent-child relationships….With full regard for th