Farm Chemicals

Parental occupational and nonoccupational exposures to pesticides have been associated with childhood cases of neuroblastoma, retinoblastoma, non-Hodgkin's lymphoma, Wilms' tumor, astrocytoma, and primitive neu-roectodermal tumors. Not all studies have shown a positive association between parental exposures in agricultural work and diseases in the offspring. However, larger studies have reported a positive association between parental occupation in agriculture and childhood brain tumors. Children of mothers who were employed as farmers or farm workers or were exposed to fertilizers, pesticides, animal manure, or unprocessed wool were more likely to have childhood brain tumors. In addition, children exposed to pigs, horses, and cats in combination with living on a farm had a threefold risk for childhood brain tumors (14-18).

Congenital anomalies associated with farm chemicals are a hazard for children whose parents live and work in agricultural areas. While most of the research has focused on the causal association between congenital anomalies and agricultural chemicals, one must also note that children with the long-term disabilities associated with these defects may be living in rural areas, giving rise to a special-needs population in remote areas. An increase in limb reduction defects, hypospadias, and epispadias was reported in an area in New Zealand where 2,4,5-T (an herbicide) was sprayed for 4 to 6 months a year. Women who resided in Imperial County, California, a highly agricultural community, were more likely to have infants with limb reduction defects than women who resided in urban areas. Malathion, an organophosphate insecticide and acaricide, has been reported to be associated with an increase in rates of gastrointestinal, limb, and orofacial defects, but these associations were not supported in a later study in which only tracheoesophageal fistulas were reported to be elevated (19-22).

In Colombia, Captan, a fungicide with structural similarities to thalidomide, was reported to be associated with a moderate increased risk of congenital malformations among occupationally exposed mothers. In an ecological study in Colorado, chromosomal defects were significantly elevated in counties with high fungicide and herbicide use, and with intensively irrigated pastureland. Heart defects were elevated in counties with intensive irrigation of pastures and cropland. Some investigators have suggested that the solvents used in the pesticide application mixture play a significant role in the teratogenic activity associated with agricultural activities. Despite substantial evidence indicating birth defects associated with pesticide exposures as an important health problem, there is virtually no published literature assessing disabilities among children on farms (23-25).

Children may have enhanced susceptibility to pesticide exposures because of their size, increased metabolism, and rapid growth. As a result, studies of adult pesticide exposure and associated adverse health effects cannot be extrapolated to children. In a qualitative study among farm-worker mothers and their children, the potential sources of exposure to pesticides were described among those aged 8 to 16 years in Colorado and Texas. The following farm activities increased the chance of exposure of children to pesticides:

1. Playing in farm fields

2. Playing in dirt near fields

3. Swimming in irrigation ditches (a big risk)

4. Being outside when fields were being sprayed with chemicals

5. Eating fruits and vegetables without washing them

6. Eating food while working in a field

7. Picking crops

8. Spraying weeds and insects (Figure 12.1)

9. Driving tractors to cut wheat and corn or to pick up trash (Figure 12.2) 10. Helping to move or feed cattle

Figure 12.1. A young man in China using a backpack sprayer to apply pesticide. Note that he is not wearing gloves, goggles, or a mask. Dermal exposure and inhalation are significant routes of exposure to pesticides. In addition, he is spraying over his head, which allows drift that can cover his body in the pesticide. His long-sleeved shirt and long pants provide some protection. However, cotton can absorb the compounds and keep them next to his skin for long periods of time if he is out spraying for several hours, thereby increasing his exposure. (Photograph by Huiling Xiang.)

Figure 12.1. A young man in China using a backpack sprayer to apply pesticide. Note that he is not wearing gloves, goggles, or a mask. Dermal exposure and inhalation are significant routes of exposure to pesticides. In addition, he is spraying over his head, which allows drift that can cover his body in the pesticide. His long-sleeved shirt and long pants provide some protection. However, cotton can absorb the compounds and keep them next to his skin for long periods of time if he is out spraying for several hours, thereby increasing his exposure. (Photograph by Huiling Xiang.)

Many of these activities clearly also may put the children at risk of an acute illness or injury (26,27).

Due to the intense use of synthetic fertilizers and livestock manure in agriculture, levels of nitrate in water may be elevated. This waterborne chemical hazard for very young children on farms results in a potential for overexposure to nitrates through drinking water. Nitrate contamination in shallow wells may lead to methemoglobinemia in infants. Nitrate is converted to nitrite by commensal bacteria in the gut and absorbed primarily in the small intestine. Levels of nitrate that are safe for adults pose a significant hazard for infants, due to the inability of the infant to process the nitrate and excrete it in the nontoxic form (28-30).

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