persistent or long-term effects. For example, Bhatnagar and colleagues (1980) studied workers at a pesticide-formulation factory in Agra, India. They compared blood samples from 42 employees who manufactured DDT, aldrin, lindane, malathion, parathion, and carbaryl with blood samples from 15 healthy subjects chosen as controls. The pesticide-exposed workers had lower hemoglobin (11 g/dL vs 14.48 g/dL). No attempt was made to control for dietary iron intake, age, sex, or other medical conditions that could have been confounding factors. It also could not be ascertained whether the observed changes were short- or long-term effects. The committee reviewed many other hematologic studies, but they did not provide information on persistent long-term health effects (e.g., Khan and Ali, 1993; Milby and Samuels, 1971; Morgan and Lin, 1978; Queiroz et al., 1999; Rosenberg et al., 1999; Straube et al., 1999; Traczyk and Rudowski, 1979; Vine et al., 2000).

Summary and Conclusion

A small number of case-control studies have examined exposure to insecticides in relation to aplastic anemia (Table 9.1). One study showed increased risk associated with exposure to a mixture of dichlorvos, propoxur, and a pyrethroid. Other studies have not shown substantially increased risks for insecticide exposure.

The committee concludes, from its assessment of the epidemiologic literature, that there is inadequate/insufficient evidence to determine whether an association exists between exposure to the insecticides under review and aplastic anemia.

TABLE 9.1 Selected Epidemiologic Studies: Aplastic Anemia and Exposure to Insecticides

Reference

Population

Exposed Cases

Estimated Relative Risk (95% CI)

Case-control Studies

Issaragrisil et al., 1997

Residents of rural Thailand

 

Organophosphate exposure

10

1.9 (0.6–5.9)

Kaufman et al., 1997

Residents of Thailand

 

 

Dichlorvos, propoxur, cyfluthrin

 

 

Any exposure

32

1.7 (1.1–2.8)

 

Regular use

17

1.6 (0.9–2.9)

 

Applied by subject

8

1.8 (0.8–4.1)

 

Carbamates

 

Any exposure

36

2.1 (1.2–3.7)

 

Regular use

19

2.0 (1.0–4.1)

 

Applied by subject

11

2.3 (0.8–6.5)

Wang and Grufferman, 1981

Residents of North Carolina in pesticide-exposed occupations

60

0.67 (0.26–1.7)

Guiguet et al., 1995

Residents of France and insecticide exposure

 

 

Hospital control comparison

18

1.6 (0.8–3.0)

 

Neighbor control comparison

4

0.4 (0.1–1.3)

Epidemiologic Studies of Aplastic Anemia and Exposure to Organic Solvents

Most of the relevant research on aplastic anemia has focused on exposure to benzene; a few studies have examined other specific solvents or solvent mixtures.



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