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Pesticide Residues Pose Different Risks to Children
Young children not only receive greater pesticide exposure, but they may
also be more susceptible to the toxic effects of pesticides as a result of their
immature physiological development. This was highlighted in a report published
in 1989 by the US Natural Resources Defence Council. A new report of the
prestigious US National Research Council, commissioned by the US Congress to
study pesticides in the diets of infants and children, confirms the cause for
concern. By Peter Beaumont.
The US National Research Council (NRC) was commissioned by the
US Congress to study scientific and policy issues concerning pesticides in the
diets of infants and children. A Committee on Pesticides in the Diets of Infants
and Children (Committee on Pesticides) was charged with responsibility for
examining what was known in the US about exposures to pesticide residues in the
diets of infants and children, the adequacy of current risk assessment methods
and policies, and toxicological issues of greatest concern(1). The enquiry was designed to find out the susceptibility of children to
pesticides.
Children are not mini-adults
Children are different from adults in that they are still developing, and have
different dietary needs and metabolism. In 1989, a study published by the
US Natural Resources Defense Council pointed out that young children generally
receive greater exposure to pesticides in food than adults(2). Relative to their
weight, children consume both more food than adults and larger quantities of
fruit—commodities more likely to be contaminated with pesticide residues. Data
from animal studies indicates that the young of many species are more likely to
retain a greater portion of a given dose of certain toxins because of increased
absorption and decreased elimination. Additionally, detoxifying enzymes are not
fully functional in the young. Finally, protein binding, a significant
detoxifying mechanism, is less well developed than in adults(3).
Greater risk in infancy
A number of laboratory studies have shown that animals are at greater risk of
developing cancer if exposure began in infancy rather than later in life. Of 14
carcinogens reviewed by the US Natural Resources Defense Council(4), the young
were more susceptible to 12. Another review found that the young were more
susceptible to 8 out of 10 carcinogens examined(5). The reasons for such
susceptibility may be linked with the rapid cell division entailed in
development and growth; but also with the fact that children have more of their
lives still to live during which exposure and carcinogenic action may occur.
Age-related susceptibility has been demonstrated for a number
of neurotoxins. Of 31 neurotoxic metals, pesticides and other organics analysed
in one review(6), there was an age-related difference in susceptibility for all
but two. In 66% of the cases where susceptibility differed with age, the young
were more susceptible. For example, they are especially susceptible to the acute
effects of organophosphate insecticides: young rats have been shown to be more
susceptible than adults to the lethal effects of 15 out of 16 organophosphate
insecticides tested. For parathion and methyl parathion the fatal dose in the
young rat is six to eight times lower in relation to body weight than in adult
rats(7).
Parental diet affects offspring
Parental diet has been shown to affect offspring. In a human developmental study
of the effects of consuming organochlorine-contaminated fish, the infants of
women who ate an average of two meals per month of fish from the US Great Lakes
were compared to those infants of the women who ate less than two such meals a
month. The children of women who ate the contaminated fish more often had a
lower birth weight, disproportionately smaller heads, and a shorter gestation
period than the children who had less exposure(8). Measurements were made later
of the powers of visual recognition of these children(9). At seven months, those
children with more exposure were less likely to recognise and look at a new
photograph after having seen one photograph. When they were tested at four years
of age, those children with more exposure had losses in short-term memory on
both verbal and quantitative tests(10).
New report confirms cause for concern
The Committee on Pesticides of the NRC studied whether toxicity tests are
sufficiently reliable in extrapolating from young or mature animals to young
children, and reviewed the current state of knowledge about perinatal and
paediatric toxicity. Neurotoxic and immune system effects can be critical
in the developing child. Cancer risk may be related to age at first exposure.
The study also looked at toxicity testing within the US registration system, the
monitoring of dietary exposure to pesticide residues in foods, and the sources
of exposure to pesticides other than in food. The monitoring data examined dated
from 1988 and earlier.
The Committee found quantitative and occasionally qualitative
differences in toxicity of pesticides between adults and children.
Qualitative differences are the consequence of exposures during vulnerable
periods of a child’s development: one example cited is exposure to
chloramphenicol in newborn babies, which leads to vascular collapse (grey baby
syndrome). The quantitative differences are due in part to age-related
differences in biological factors such as absorption or metabolisation.
The extent of toxicity is also related to size, immaturity, and variation in
body composition. The relative differences in toxicity between children and
adults were about 10-fold.
The Committee also found that infants and children differed
both qualitatively and quantitatively from adults in their exposure to pesticide
residues in foods. However the Chair of the Committee, Dr. Philip
Landrigan stressed that: “Our report should not be a cause for alarm . .
. children should eat a wide variety of fruit and vegetables to get the vitamins
and minerals they need, but the regulatory system needs to be changed.”(11)
Regulations need tightening
The report recommended that:
- changes be made in US regulatory practice, so that
estimates of expected total exposure to pesticide residues should reflect
the unique characteristics of the diets of infants and children and should
also account for non-dietary intakes of pesticides;
- EPA modify its decision-making process for setting
tolerances so that it is based more on health considerations than
agricultural practices;
- new methods of cancer risk assessment should be developed
to account for changes in exposure and susceptibility that occur as a person
matures.
The report argues that the conventional ‘safety factor’ that allows for the
uncertainty in extrapolating results from animal testing to humans, and for the
variation and differences in sensitivity between humans, should be increased by
an additional factor of 10 when there is evidence of postnatal toxicity of the
pesticide, or when data from toxicity testing relative to children are lacking.
Under-reporting on pesticide residues
Pesticides in children’s food is the subject of a further report from the
Environment Working Group, a non-profit environmental research organisation(12).
Using more recent data from the period 1990-92, the report looks at the patterns
of food consumption of young children, and the monitoring capabilities of US
Food and Drug Administration (FDA) laboratories. It considers that FDA seriously
under-reports pesticide residues in the food supply. From 80% to 100% of residue
analysis at five of 12 FDA regional laboratories were not capable of finding 80%
of the pesticides used in agriculture.
This report, which also considered the
exposure of children to pesticides that the US EPA considers probable or
possible human carcinogens, estimated that millions of US children receive up to
35% of their entire lifetime dose of some carcinogenic pesticides by age five.
This pattern is most evident for pesticides used on foods heavily consumed in
the first years of life—in the US these are the fungicides captan (35% of
lifetime risk by age 5) and benomyl (29%) and the insecticide dicofol (32%).
In contrast to the NRC report, the
Environment Working Group does not see a change in regulatory procedures as the
way forward. It also stresses the importance of continuing to eat fresh fruit,
vegetables, and other staples, but advocates reducing the use of pesticides in
food production, including:
- a targeted pesticide risk reduction strategy that will
gradually phase out the use of pesticides that present the greatest hazards
to children—including all those classed by the EPA as known carcinogens or
potential carcinogens;
- a programme of research for agricultural producers to help
them develop alternative pest control practices for high-risk pesticide/crop
combinations;
- steps to expand consumer access and farmer markets for
foods produced with fewer pesticides, and that contain no residues,
including the establishment of national organic standards, and a voluntary
‘no-detected’ or ‘ultra-low’ standard for pesticide residues in
food.
Response from the Clinton Administration
Responding to both reports, EPA’s Administrator Carol Browner together with
the FDA and the US Department of Agriculture, announced its commitment to
reducing the use of pesticides, and to promoting sustainable agriculture,(13)
although exactly how was not specified. Both reports would be used “as a basis
for formulating the legislative and regulatory policies needed to put the
Administration principles into effect.”
The UK position
Of the three pesticides identified in the Environment Working Group’s report,
benomyl is widely used in horticulture, captan has considerably fewer uses and
dicofol has no approved uses. Residue monitoring is more up-to-date than the
data used by the NRC, and UK authorities differ from the US EPA as to what
pesticides are carcinogens. Nevertheless, a number of concerns remain.
- Does the UK consider that the pesticides identified
in the Environment Working Group report are carcinogens and pose a cancer
risk to children?
- Does the UK consider valid the NRC recommendation that
methods of cancer risk assessment be developed to account for changing
exposure and susceptibility that occur as a person matures?
- Should changes be made to UK regulatory and farming
practices, so that estimates of expected total exposure to pesticide
residues reflect the unique characteristics of the diets of infants and
children and non-dietary intakes of pesticides?
The Pesticides Trust [now PAN UK] has written with these concerns to the
UK’s Advisory Committee on Pesticides, the independent body of scientists that
advises government ministers. The ACP has since replied saying it will examine
in detail the NRC report at future meetings.
- References:
- 1. National Research Council, Pesticides in :the Diets
of Infants and Children, National Research Council Committee on Pesticides
in the Diets of Infants and Children. National Academy Press, Washington,
386 pp., $47.95, 1993. (Available from NAS Office of News and Public
Information, 2101 Constitution Avenue NW, Washington DC 20416, USA, Tel: 800
24-6242).
- 2. Natural Resources Defense Council, Intolerable Risk:
Pesticides in Our Children's Food. NRDC, Washington, 1989.
- 3. Calabrese, E.J., Age and Susceptibility to Toxic
Substances. John Wiley and Sons, New York, 1986.
- 4. Whyatt, R., 'The Physiological Susceptibility of
Children to Pesticides.' Journal of Pesticides Reform, 9:3, pp. 5-9, 1989.
- 5. Calabrese, op. cit.
- 6. Calabrese, op. cit.
- 7. Murphy, S.D., 'Toxicity and Hepatic Metabolism of
Organophosphate Insecticides in Developing Rats.' In Hunt, V.R., et al. (eds),
Banbury Report 11: Environmental Factors in Human Growth and Development.
Cold Spring Harbour Laboratory, New York, 1983.
- 8. Fein, G., Jacobson J., et al., 'Prenatal Exposure to
Polychlorinated Biphenyls: Effects on Birth Size and Gestational Age.'
Journal Pediatr., 105, pp. 315-20, 1984.
- 9. Jacobson, S.W., Fein, G.G., et al., 'The Effect of
Intrauterine PCB Exposure on Visual Recognition Memory.' Child Dev., 56, pp.
853-60, 1985.
- 10. Jacobson, J., Jacobson, S., et al., 'Effects of In
Utero Exposure to Polychlorinated Biphenyls and Related Contaminants on
Cognitive Functioning in Young Children.' Journal Pediatr., 116, pp. 38-45,
1990.
- 11. National Research Council, Changes Needed to Protect
Children from Pesticides in Diet, NRC Press Release, 28 June 1993.
- 12. Environmental Working Group, Pesticides in
Children's Food. R. Wiles & C. Campbell, 88pp, $15, 1993.
Available from Environmental Working Group, Agricultural Pollution
Prevention Project, 1718 Connecticut Ave, NW, Suite 600, Washington DC 20009
USA (Tel: 202 667-6982, fax 202 2332-2592).
13.
Joint Press Release, EPA, FDA, and USDA, 25 June 1993.
[This article first
appeared in Pesticides News No.21, September 1993 pages 4-5]
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