Environment and Chemicals
Researchers from the Harvard School of Public Health suggested in 2006 that
fetal and early childhood exposures to chemicals in the environment
can damage the developing brain and can lead to
neurodevelopmental disorders. They described
202 chemicals that have the capacity to damage the human brain and concluded
that chemical pollution may have harmed the brains of millions of children
Concern about disease-causing effects of agricultural chemicals has been
expressed for several decades. In 1982, for example, Alan Anderson
[ii] reviewed the importance of nervous system toxins from
the environment in causing mental malfunction. He stated:
"Of the 100,000 or so chemicals used by American industry, 575 are deemed dangerous in large
doses and many of these are known to be associated with catastrophic illness,
from cancer to respiratory disease. Perhaps no class of chemicals is more subtle
and treacherous in its effects, however, than neurotoxins, which can damage the
nervous system even in modest doses and cause a variety of behavioral and
emotional symptoms - among them, hallucinations, loss of memory, confusion,
depression and psychosis."
There are several groups of pesticides used to control insects, weeds, and
fungi. The chemicals are classified by target organisms as insecticides,
herbicides, fungicides, or fumigants. Insecticides are classified by chemical
type as organophosphates (OPs), organochlorines, carbamates, and pyrethroids.
Direct exposure to these chemicals when they are spayed on crops, forests,
residential area, and used in and around the home are more obvious and more
toxic that indirect exposure to low concentrations by drinking contaminated
water and eating contaminated food. The effect of agricultural chemical
contamination of the food supply is not known. Individual sensitivity to
contaminant chemicals varies and is interactive with other chemical stressors.
Some pesticides are longer-lasting than others and can be generally distributed
in the environment. DDT use, for example, is banned in North America, still
shows up, carried on air currents from distant countries who continue to use it.
Organochlorines have a long half-life, and serum levels can be used as a general
marker of exposure to pesticides.
The biological effects of low levels of agricultural chemicals in the human
body are uncertain. No authority can assure you that all is well.
[iii] Chronic exposure to low but cumulative doses of
chemicals may lead to chronic illness, and sooner or later, avalanche into
catastrophic illness. People who use pesticides on regular basis risk toxicity
and should reconsider this use. Individuals are frequently exposed to many
different pesticides or mixtures of pesticides repeatedly over many years.
Common pesticides (Malathion, Parathion, EPN, Schradan) are
related to nerve gases (Saran, Soman), which all block the breakdown of
acetylcholine in synapses, so that it accumulates and blocks receptors.
The result of a large dose is respiratory failure and convulsions, quickly fatal
if the dose is high enough. Acute poisoning would only occur in people exposed
to high concentrations of these chemicals in agriculture and industry. Kamel and
Hopping summarized the problem: “Pesticides are used extensively throughout the
world. In the United States, more than 18,000 products are licensed for use, and
each year more than 2 billion pounds of pesticides are applied to crops, homes,
schools, parks, and forests.
Such widespread use results in pervasive
human exposure. Evidence continues to accumulate that pesticide exposure is
associated with impaired health. Occupational exposure is known to result in an
annual incidence of 18 cases of pesticide-related illness for every 100,000
workers in the United States. The best-documented health effects involve the
nervous system. The neurotoxic consequences of acute high-level pesticide
exposure are well established: “Exposure is associated with a range of symptoms
as well as deficits in neurobehavioral performance and abnormalities in nerve
function. Whether exposure to more moderate levels of pesticides is also
neurotoxic is more controversial. Pesticide exposure may also be associated with
increased risk of neurodegenerative disease, particularly Parkinson disease.”
Sixteen pesticides have been detected in eight brand-name baby foods In the
USA, according to a study by the Environmental Working Group (EWG) and the
National Campaign for Pesticide Policy Reform (1997). A random sampling of 76
jars of baby food from grocery store shelves in Denver, Philadelphia, and San
Francisco revealed that 53% had traces of one pesticide, and 18% had two or more
pesticides. Plums contained the highest amounts at 46 parts per billion and
peaches contained 29 parts per billion. The EWG was concerned that pesticides
are not “tested for safety in the way babies are exposed to them," and that
babies and young children "react differently than adults to many drugs and toxic
Lead, mercury compounds, pesticides, herbicides, fungicides, aluminum,
styrene, tetrachlorobiphenyl, and dioxins are among the neurotoxins that may be
airborne and contaminate the food supply. The Environmental Protection Agency in
the USA reported that the magnitude of chemical contamination of the USA in 1987
was 9.7 billion pounds of chemicals into streams and 2.7 billion pounds into the
air. The allowance of toxic chemicals for each citizen was about 50 pounds.
Despite concern about chemical toxicity, little has changed in the last 3
decades except that more chemicals have been added to the environment.
Individual sensitivity to contaminant chemicals varies and is interactive with
other chemicals entering the body.
[i] Grandjean et al. Developmental neurotoxicity of
industrial chemicals. Lancet.
Nov. 8, 2006. Also see online Department of
Environmental Health, Harvard School of Public Health, Boston, MA, USA
Silent Pandemic: Industrial Chemicals Are Impairing the Brain Development of
Children Worldwide. http://www.hsph.harvard.edu/neurotoxicant/appendix.doc
[ii]Anderson A. Neurotoxic Follies. Psychology Today
July 1982: 30-42
[iii]Morgan DP Minimizing occupational exposure to
pesticides: acute and chronic effects of pesticides on human health Residue
Reviews 1980; 75:97-102 Springer-Verlag N.Y.
[iv] Freya Kamel; Jane A. Hoppin. Association of
Pesticide Exposure With Neurologic Dysfunction and Disease.
Perspect 112(9):950-958, 2004. © 2004 National Institute of Environmental Health
Sciences. Freya Kamel and Jane A. Hoppin are at the National Institute of
Environmental Health Sciences, National Institutes of Health, Department of
Health and Human Services, Research Triangle Park, North Carolina, USA .