(Beyond Pesticides, August 8, 2007)
For the first time, the World Health Organization (WHO) released a report in July on children’s heightened vulnerability to chemical exposures at different periods of their growth and development. The organization cites over 30% of the global burden of disease in children can be attributed to environmental factors, including pesticides.
The report, Principles for Evaluating Health Risks in Children Associated with Exposure to Chemicals, is a new volume of the WHO’s Environmental Health Criteria series. It highlights the fact that for children, the stage of their development when chemical exposure occurs may be just as important as the magnitude of the exposure. In respect to pesticides, the report cites several studies that tie pesticide exposure during key periods of development to neurobehavioral problems, Parkinson’s disease, and immunotoxicity, including respiratory diseases.
“Children are not just small adults,” said Dr. Terri Damstra, Ph.D., WHO’s team leader for the Interregional Research Unit, in WHO’s press release. “Children are especially vulnerable and respond differently from adults when exposed to environmental factors, and this response may differ according to the different periods of development they are going through.”
Air and water contaminants, pesticides in food, lead in soil, as well many other environmental threats may cause or worsen disease and induce developmental problems. The report notes that children have different susceptibilities during different life stages, referred to as “critical windows for exposure” or “critical windows of development,” due to their dynamic growth and developmental processes, as well as physiological, metabolic, and behavioral differences. Exposure can occur:
- In utero through transplacental transfer of environmental agents from mother to fetus or in nursing infants via breast milk.
- Through diet – children consume more food and beverages per kilogram of body weight than do adults, and their dietary patterns are different and often less variable during different developmental stages.
- Through inhalation and absorption – children have a higher inhalation rate and a higher body surface area to body weight ratio, which may lead to increased exposures.
- Through behavior – children ‘s normal behaviors, such as crawling on the ground and putting their hands in their mouths, can result in exposures not faced by adults.
- Other physical factors – children’s metabolic pathways may differ from those of adults, and children have more years of future life and thus more time to develop chronic diseases that take decades to appear and that may be triggered by early environmental exposures.
- Also, children are often unaware of environmental risks and generally have no voice in decision-making.
Some examples of health effects resulting from developmental exposures prenatally and at birth include miscarriage, still birth, low birth weight and birth defects; in young children, infant mortality, asthma, neurobehavioral and immune impairment; and in adolescents, precocious or delayed puberty. Evidence also suggests that an increased risk of certain diseases in adults such as cancer, chronic respiratory disease and heart disease can result in part from exposures to certain environmental chemicals during childhood.
Traditional risk assessment approaches and environmental health policies have focused mainly on adults and adult exposure scenarios, utilizing data from adult humans or adult animals. The report highlights there is a need to expand risk assessment paradigms to evaluate exposures relevant to children from preconception to adolescence, acknowledging each developmental stage.
The study, while pointing out risk assessment is flawed and encouraging new and improved research, also states “A lack of full proof for causal associations should not prevent efforts to reduce exposures or implement intervention and prevention strategies.”
Real world exposure is indeed complicated and makes it difficult to conclusively draw causal associations, especially taking into account synergistic effects, etc., leaving a clear and vital need to exercise the precautionary principle. The easiest and safest solution regardless of risk assessment methods is to avoid chemical use and exposure by using alternative, non- and least toxic management methods for species that can cause economic and health problems, being more tolerant of species that are solely a nuisance or aesthetically displeasing, and using organic products, especially foods.