toxicological profile for malathion - Agency for Toxic Substances and ...

MALATHION 70
3. HEALTH EFFECTS
approximate dose of 0.11 mg malathion/kg/day for 32 days, 0.23 mg malathion/kg/day for 47 days, or
0.34 mg malathion/kg/day for 56 days (Moeller and Rider 1962).
Limited information exists regarding renal effects in animals following oral exposure to malathion. A
single gavage dose of 1,950 mg/kg malathion (95% pure) (only level tested) induced kidney congestion in
male Wistar rats during 2 days after dosing and kidney enlargement on the second and third day
(Piramanayagam et al. 1996). Microscopically, the kidneys showed hyperemia, degeneratives changes in
the tubular epithelium, and microgranuloma. Without specifically mentioning the kidneys,
Piramanayagam et al. (1996) indicated that by day 12 after dosing, almost all organs appeared normal.
Treatment of rats by gavage with ≥130 mg malathion/kg/day (purity unspecified) for 1–2 weeks induced
atrophy of the glomeruli, degeneration of the tubular epithelium, and epithelial casts (Piramanayagam and
Manohar 2002). A lower dose of 75 mg/kg/day of malathion (95%) in the food for 90 days had no
significant histopathologic effects on the kidneys from female CFY rats (Desi et al. 1976).
Other studies have provided information of biochemical parameters in the kidney of unclear toxicological
significance. Increased lipid accumulation and decreased glutathione content were reported in female
Sprague-Dawley rats following three gavage doses of 500 mg/kg/day malathion (98% pure) (Prabharakan
and Devi 1993; Prabhakaran et al. 1993). A 32-day gavage study in rats reported increased AST, ALT,
and AP enzyme activities in the kidneys (Husain et al. 1987). An additional study in Sprague-Dawley
rats reported increased blood urea nitrogen (BUN) after 5 weeks of treatment with approximately
0.067 mg/kg/day malathion (98%) pure bound to milled rice (Syed et al. 1992). Increased BUN may
indicate glomerular disease, but may also have many other causes unrelated to kidney function.
None of the long-term studies reported any significant kidney lesions in rats administered malathion in
doses of up to 622 mg/kg/day (NCI 1978) or in mice administered up to 2,980 mg/kg/day (NCI 1978).
However, increased absolute and relative kidney weight was reported in male and female Fischer-344 rats
administered 359 or 415 mg/kg/day of malathion (97.1% pure), respectively, in the diet for 2 years (Daly
1996a); the corresponding NOAELs were 29 and 35 mg/kg/day. The available information in animals
suggests that the kidney is not a sensitive target for malathion toxicity.
Endocrine Effects. The only relevant information available of endocrine effects in humans is that
from a study of 22 patients with organophosphate poisoning that resulted from intentional ingestion of
undetermined amounts of malathion (Güven et al. 1999). Upon admission to the hospital, all patients
showed signs of organophosphate intoxication. Blood levels of several hormones, particularly pituitary