TABLE 3-1 Summary of Epidemiologic Studiesa


Study Design



Adjustment Factors


Major Findings


Studies of Occupational Groups and Adult Cohorts

Rockette and Arena 1983

SMR study, 1970-1978

3,963 chemical workers, 94% male

Magnesium perchlorate, unknown amount, in combination with 23 other chemicals

Age, calendar time

Cause-specific mortality

For males 1970-1978, all cancer SMR = 143.7, p < 0.01; respiratory cancer SMR = 169.6, p < 0.01; stomach cancer SMR = 236.7, p < 0.05

Very few deaths recorded in females, so only data on males analyzed in detail; multiple chemical exposures; no adjustment for cigarette-smoking or potential confounders other than age

Gibbs et al. 1998

Repeated cross-sectional (preshift and postshift)

18 workers exposed to ammonium perchlorate and 83 nonexposed workers

Respiratory exposure at 0.2-436 µg/kg, depending on work area

Duration of shift

Compared preshift and postshift serum free T4 index, total T4, and TSH

No significant relation of perchlorate dose to change in thyroid hormone and TSH measures across shift

Respiratory exposure; small number of exposed workers; subject to potential bias of affected workers who left employ ment before study

Gibbs et al. 1998

Historical cohort

53 high dose, 44 low dose, 192 nonexposed

Lifetime cumulative exposure to perchlorate; mean in “low-dose” group, 3,500 µg/kg; mean “high-dose,” 38,000 µg/kg


Compared medical records on thyroid hormone and TSH measures and disease; medical surveillance data from cohort

Neither estimated cumulative lifetime exposure nor exposure category significantly associated with abnormalities of thyroid hormone measures and TSH

Respiratory exposure; subject to potential bias of affected workers who left employment before study; no statistical adjustment for BMI or activity level

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