Neurotoxicology and Teratology 24 (2002) 467 – 469 www.elsevier.com/locate/neutera
Research ethics in pediatric environmental health Lessons from lead Howard W. Mielke* Division of Basic Pharmaceutical Sciences, College of Pharmacy, Xavier University of Louisiana, 70125 New Orleans, LA, USA Received 9 January 2002; accepted 4 April 2002
From my perspective, the ethical problems in pediatric environmental health research stem from a profound societal lack of understanding about the role that environment plays on health. An Institute of Medicine report states the environmental health hypothesis as follows: ‘‘Healthy environments promote individual and community health; unhealthy environments can create substantial morbidity, mortality, and disability, in addition to sapping economic welfare of societies’’ . The connection between the environment and health is amply illustrated by lead. The purpose of my contribution is to describe empirical research findings as they pertain to lead and to explore the ethical consequences for failing to apply the environmental health hypothesis toward treating this preventable disease. Empirical research about the connection between community lead contamination and environmental health is from a series of studies conducted in New Orleans, LA, beginning in 1989 and being concluded in 2002. The exceptional sensitivity of young children to lead is related to their crawling and hand-to-mouth behavior plus their physiological need for minerals such as calcium and iron . Children are super efficient absorbers of environmental minerals, and excessive lead absorption is one of the manifestations of these childhood characteristics. In addition to neurotoxicity, childhood exposure has long-term consequences to the immune and respiratory systems . The total tolerable daily intake for lead is about 6 mg/day for very young children . One of the first empirical studies we conducted was on the amount of lead children pick up on their hands during indoor and outdoor play at daycare centers of New Orleans. The usual approach for studying lead exposure is to screen children’s blood lead. Inserting needles into veins is traumatic to many children, and for this and other reasons, studies involving blood lead screening have been prohibited by most daycare centers. As an
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alternative approach for evaluating environmental health we developed a protocol for a hand wipe study of children that was benign and provided direct information to the owners of the daycare center about environmental trouble spots on their property . Each child was its own control. First children’s hands were wiped after playing indoors. Then, the children went outdoors. Finally, the children’s hands were wiped a second time as they were returning inside from the outdoor play area. At private daycare centers in the inner city, the indoor play resulted in an average of 4 mg lead per hand, while outdoor play resulted in 28 mg lead per hand. In the outer city, children had an average of 3 mg lead per hand inside and 4 mg per hand after outdoor play. It is important to note that private daycare centers had bare soils. The study also included public daycare (Head Start) centers where the outdoor play areas had rubberized ground cover and no bare soils. In that situation there was only a small increase (from 1.4 to 1.9 mg lead averages per hand) between indoor and outdoor play . We reasoned that on ordinary inner-city private properties children pick up and ingest more lead than children living in outer-city locations because the inner-city environment, especially outdoor play areas, contained larger quantities of accessible lead. While daycare centers may differ from ordinary homes, the findings are suggestive of the broader environmental health situation; lead-contaminated environments are linked with unhealthy levels of lead exposure by children. Further empirical research was conducted to test the environmental health hypothesis. Our studies focused on surveying the distribution of lead in the residential environment of the entire city of New Orleans located on the Mississippi River delta. New Orleans soils are of alluvial origin, meaning that they were transported as sediments by the Mississippi River from the entire watershed and were subsequently deposited (as alluvium) during annual flooding in the river delta. The fresh alluvium deposited along the river provides a measure of the modern background. The median background of alluvial soil lead is about 5 mg/g
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H.W. Mielke / Neurotoxicology and Teratology 24 (2002) 467–469
(i.e., ppm) (range 1.7– 22.8). This quantity is 1/24th the median lead (120 ppm, range < 1 –191,000) of metropolitan New Orleans alluvial soils [9,11]. The residential soils of the total New Orleans metropolitan area were mapped for lead. The soil analytical results were stratified by census tracts (see Fig. 1). Then, the results of the 1996 Louisiana blood lead screening program were used to evaluate the association between children and the amount of lead in the environment. At the same time, we considered the association between children and age of housing by census tract. The analysis showed that age of housing was acceptable ( p = 10 12) for predicting the communities of the city with highest blood lead levels, but that newer housing did not reliably predict communities with lower exposures . On the other hand, soil lead was superior ( p = 10 24) in predicting the exposures of children in communities . That study was followed up by a study that mapped the areas of the city where children’s lead exposures were higher and places where children’s exposures were lower, and overall, Fig. 1 describes the pattern of childhood lead exposure in New Orleans . Perspective on the effect that environmental lead has on the children of New Orleans is suggested by a preliminary evaluation of elementary school achievement scores of students in two school attendance districts, both predominantly African American . District A has a median lead content of 405 ppm, while District B has a median lead content of 152 ppm. In District A, the school performance score is 23.6 (meaning that about 75% of the children are failing), while in District B, the school performance score is 75.8 (or about 25% of the children failing) . As indicated by many studies, lead is a neurotoxin that strongly influences learning and behavior . To reiterate Pope and Rall , ‘‘. . . unhealthy environments can create
substantial morbidity, mortality, and disability, in addition to sapping economic welfare of societies.’’ In New Orleans, there is strong evidence that excessive environmental lead is associated with disability and the sapping of economic welfare. Conducting blood lead screening of children and then, if their blood lead is elevated above the guideline at the time, treating the source (usually thought of as paint) is fraught with serious ethical and social problems. Given our current understanding about measuring environmental lead, it is unconscionable to use children as bioindicators of environmental lead. We have explored hand lead, surveyed the lead accumulation in the environment, found a strong association between the environment and children’s exposure and undertaken a preliminary examination of school performance consequences of unhealthy environmental lead. Currently, 25 – 30% of the children of New Orleans are exposed at 10 mg/dl or higher blood lead, and there is no known medical treatment to reverse the effects of exposure . Once exposed, the children are left with various degrees of intellectual and social disabilities. The only known treatment is primary prevention. This means identifying and treating a variety of environmental sources in living spaces, both indoor and outdoor, to prevent children from becoming exposed to lead. As a starting point, prevention must focus on the legacy of two major lead products, dust from lead-based paint and residual dust that settled in the city from the use of lead in gasoline [7,13]. Soils integrate all sources of lead, and mapping soil lead is an excellent tool for accessing the environmental health of communities and setting priorities for cleanup . Changing the focus of pediatric environmental health research toward understanding the role that environment plays on health would emphasize primary prevention of exposure sources and diminish the unethical and senseless practice of using children as bioindicators of environmental lead contaminants. Fortunately, environmental medicine (also known as medical geology) is an active topic of research with many examples of success in identifying and treating environmental diseases [4 – 6,8,14,18]. Collaborative efforts in using environmental measurements (dust wipes and tests of other media) instead of blood lead screening for detecting lead hazards shifts the focus away from the ethically untenable position of using children as bioindicators of unhealthy environments.
Acknowledgments Fig. 1. Distribution of lead in metropolitan New Orleans. The mapping was done by interpolation (kriging) of census tract centroids with their assigned median values for soil lead. Note the high lead values in the first ring of inner-city communities and the reduction of lead as distance increases from the paved over central business district of New Orleans. Empirically, children’s exposure to lead is strongly associated with the integrated lead that has accumulated in soil ( p = 10 24).
The research on hand lead was funded by the National Institute of Environmental Health Sciences (Grant no. P20 ES06435) and research on the environment of New Orleans was funded by an ATSDR/MHPF cooperative agreement no. U50/ATU398948 to Xavier University. Christopher Gonzales developed Fig. 1 at Xavier University.
H.W. Mielke / Neurotoxicology and Teratology 24 (2002) 467–469
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