Worldwide, as much as two thirds of all preventable ill health due to environmental conditions occurs among children (1). Children most affected belong to impoverished populations living in rural and peri- urban areas in developing countries. Currently, many of these children are exposed not only to biological hazards associated with lack of access to a clean environment, but also to toxic chemicals and other pollutants that stem from uncontrolled development. These pollutants include agrochemicals, industrial chemicals such as polychlorinated biphenyls (PCBs), heavy metals such as lead and arsenic, and a variety of air pollutants. These substances have been linked with birth defects, cancer, and weakening of the immune system.
The risk for contracting environmentally related illness is altered by several factors including a person’s genetic background, nutritional status, age, lifestyle, and income level. Age is a major determinant of risk because the processes that determine exposure, absorption, metabolism, excretion, and tissue vulnerability are all age-related. The metabolism of infants and children differs from those of adults, as do their physiological and biochemical processes (2).
Susceptibility – the capacity to be affected – is a key factor in determining environmental risks to children. It also varies among different populations, ethnic groups, and genetic backgrounds, as well as by age, experience, and development. The combination of increased susceptibility and increased opportunity for exposure to a particular set of environmental threats – such as some pesticides and air pollutants – can increase health hazards for children (3).
Exposure to environmental agents is the first step in the sequence of environmentally related health effects. Exposures to these agents can occur even before conception, if the mother is exposed to certain pollutants that cross the placenta, such as lead or mercury. Exposures vary depending on one’s physical location, breathing zones , oxygen consumption, and behavioral and eating patterns, all of which can change several times before an individual reaches adulthood.
The sources and routes of exposure to toxic substances for children are multiple. Some exposures are occupationally related – when children work in fields sprayed with pesticides, for instance, or when parents carry home chemical residues on clothing, or when chemicals to which the mother is exposed at work are transferred via breast milk to the child. Still other exposures can come from discharges to the air and water, certain waste sites, and on occasion, industrial accidents (4).
Because they have higher metabolic rates than adults, children breathe more air – twice as much per pound of body weight – than adults. In addition, children breathe air that is closer to the ground, where concentrations of contaminated dust can be higher. When children are more active, they inhale more deeply and may deposit pollutants deeper into their lungs than adults. These particles are more readily retained in the lungs and absorbed (5).
The maximum concentration of air pollutants recommended by the World Health Organization (WHO) is routinely exceeded in many Latin American cities including São Paulo and Rio de Janeiro, Brazil; Santiago, Chile; and Mexico City. Approximately 76 million people in Latin American cities are exposed to levels of suspended particulates well beyond maximum allowable levels. Annually in this region, as many as 3 million cases of chronic coughing in children have been attributed to this cause (6).
Poor indoor air quality is a major contributor to disease in the developing world, especially among low-income women and children whose families cook with biomass fuels. Worldwide, an estimated 3 million premature deaths, mostly due to acute and chronic respiratory infections, have been attributed to foul air; of these deaths, 2.8 million are due to indoor air pollution and 90 percent occur in developing countries (7).
Exposure of children to lead and persistent organic pollutants is another particular concern. Although mounting evidence shows that many developed countries have reduced human exposure and health risks of toxic chemicals such as lead, cadmium, mercury, DDT, and PCBs, in other parts of the world these problems have yet to be addressed (8).
Children are also likely to be exposed to higher levels of toxics from agrochemicals than are adults. Children are particularly vulnerable to health damage from some agrochemicals. A child’s susceptibility is greater between conception and age 5, before organ systems and other functions mature, such as the liver’s detoxification potential and the kidneys’ filtration potential. Because those body cells are reproducing rapidly, children may be especially vulnerable to carcinogens. Likewise, children may be more susceptible to loss of brain function if exposed to neurotoxins during critical periods of development, as suggested by studies on lead, methyl mercury, PCBs, and dioxin (9).
Because the dietary diversity of most very young children is low – consisting of breast milk, infant formula and/or cow’s milk first, and then fruit juices together with pureed fruits and vegetables before finally switching to the table foods of their parents – their exposure to agrochemical residues in both water and foods may often be higher than that of adults. For example, children in the United States eat up to seven times more of certain fruits in proportion to their body weight (10).
Children of farmworkers are believed to be at elevated risk of pesticide exposure. Particularly in developing countries, peasant children may work in the fields alongside their parents, and infants are sometimes carried and breast-fed by their mothers while at work. Pesticide contamination of breast milk has been found even in remote villages in Papua New Guinea and India. Studies have shown that women in developing countries suffer the greatest exposure to pesticide residues (11).
It is clear that children are exposed to certain chemicals more than adults and that certain of their organs and biological functions are more susceptible to damage during specific phases of their development. However, the poor quality of information on food consumption, plus the inconclusive data on pesticide residues and toxicity, make it impossible to establish with any certainty the health risks for children. It is likely, however, that where general standards for pesticide exposure levels have been set, they may be inadequate for protecting children.
References and notes
1. World Health Organization (WHO), Health and Environment in Sustainable Development: 5 Years After the Earth Summit (WHO, Geneva, 1997), p. 199.
2. Cynthia F. Bearer, “How Are Children Different From Adults?” in National Institutes of Health/National Institute of Environmental Health Sciences Environmental Health Perspectives Supplements, Vol. 103, Supplement 6 (1995), pp. 7-12.
3. Lynn R. Goldman, “Children – Unique and Vulnerable: Environmental Risks Facing Children and Recommendations for Response,” in National Institutes of Health/National Institute of Environmental Health Sciences Environmental Health Perspectives Supplements, Vol. 103, Supplement 6 (1995), pp. 13-18.
4. Ibid., p. 16.
5. Robin Meadows, “Growing Pains,” in National Institutes of Health/National Institute of Environmental Health Sciences Environmental Health Perspectives Supplements, Vol. 104, No. 2 (1996), p. 147.
6. Henyk Weitzenfeld, “Contaminación atmosférica y salud en América Latina, Bolétin de la Oficina Sanitaria Panamericana, Vol. 112, No. 2 (1992), pp. 97-109.
7. Op cit. 1, p. 87.
8. Op cit. 1, p. 201.
9. John Wargo, Our Children’s Toxic Legacy: How Science and Law Fail to Protect Us from Pesticides (Yale University Press, New Haven, Connecticut, 1996), pp. 11-12.
10. Op cit 5.
11. Pratap Chatterjee, “Pesticide Poison Circles the Globe,” Panoscope, No. 39 (April 1994), p. 24.
