m-PHTHALODINITRILE

OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.

CAS: 626-17-5; Chemical Formula: C₈H₄N₂

OSHA has no previous limit for m-phthalodinitrile. The proposed PEL was 5 mg/m³ as an 8-hour TWA, and this limit is established in the final rule. NIOSH (Ex. 8-47, Table N1) concurred with the selection of this PEL. The ACGIH has a TLV-TWA of 5 mg/m³ for this substance. meta-Phthalodinitrile exists in the form of needles obtained from solutions containing either water or ligroin as the solvent.

In rabbits, slight skin reactions have been reported from dermal applications of m-phthalodinitrile to intact or abraded skin for six hours/day, five days/week over a three-week period. The doses applied were 0.5, 1.0, and 2.0 g/kg; at the two higher dose levels, some changes in organ (unspecified) size, without histopathologic changes, were observed. Female rabbits exposed at the highest dose lost weight (Owen 1972, as cited in ACGIH 1986/Ex. 1-3, p. 488).

A 15-year review of industrial experience revealed no reports of adverse effects from exposure to m-phthalodinitrile (Zeller,Hofmann, Thiess, and Hey 1963, as cited in ACGIH 1986/Ex. 1-3, p. 488). Williams (1959/Ex. 1-1176) attributes this absence of exposure effects to the fact that the aromatic nitriles, of which m-pthalodinitrile is one, do not liberate cyanide in the body, as is the case with the aliphatic nitriles. No comments other than NIOSH’s were received by OSHA on this substance.

OSHA is establishing an 8-hour TWA limit form-phthalodinitrile of 5 mg/m³. The Agency concludes that this limit will protect exposed workers from the significant risk of skin irritation, a material health impairment that exists at m-phthalodinitrile levels above the new limit.