SIAM 18, 20-23 April 2004
SIDS INITIAL ASSESSMENT PROFILE
SUMMARY CONCLUSIONS OF THE SIAR
Maleic anhydride is readily hydrolyzed to maleic acid under aqueous conditions.
As a result, these two chemicals are
presented because of the conditions used to test their toxicity.
The only difference may be due to the potential for
maleic anhydride to form haptens by acylating with amino acids, resulting in an immunological response (dermal and
Maleic anhydride and maleic acid exhibit relatively low acute toxicity by the oral and dermal routes, with the oral
of about 1.0 g/kg in rats and an acute dermal LD
in the range of 1.6 to 2.6 g/kg in rabbits.
and maleic acid have been reported to be severely irritating to the skin and eyes of rabbits.
Maleic anhydride has
been shown to be a skin sensitizer to guinea pigs and a possible respiratory sensitizer to rats.
There have been a few
published human cases suggesting that maleic anhydride provokes asthma in a relatively small proportion of exposed
workers; however, questions have been raised about whether the asthma was related to maleic anhydride exposure.
Although no sensitization data exist for maleic acid, it is not predicted to be either a skin or respiratory sensitizer.
Repeated exposure of maleic anhydride by inhalation to rats, hamsters, and monkeys have resulted in effects that were
limited to the respiratory tract and eye irritation.
In a four-week study, rats exposed six hours/day to 0, 12, 32, and 84
(0, 3, 8, 21 ppm) maleic anhydride showed evidence of nasal, trachea, and lung irritation at all exposure levels.
These effects were concentration-related and included epithelial hyperplasia and the presence of inflammatory
exudates in the nasal turbinates and trachea; and epithelia hyperplasia, squamous metaplasia, and intra-alveolar
hemorrhage in the lung.
Increased incidence of hemorrhagic lung foci were also observed in the 32 and 86 mg/m
The LOAEL was 12 mg/m
In a six-month inhalation study in which rats, hamsters, and
monkeys were exposed to 0, 1.1, 3.3, or 9.8 mg/m
(0, 0.3, 0.8, or 2.4 ppm), respiratory tract and eye irritation were
observed in rats and hamsters exposed to 3.3 or 9.8 mg/m
(0.8 or 2.4 ppm) and monkeys to 9.8 mg/m