ROSIN CORE SOLDER

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: None; Chemical Formula: None

OSHA previously had no limit for rosin core solder pyrolysis products. Based on the ACGIH TLV, the Agency proposed an 8-hour TWA of 0.1 mg/m³ for these compounds, measured as formaldehyde. OSHA has determined that a TWA limit of 0.1 mg/m³ is necessary to prevent workers from experiencing severe irritant reactions, and the Agency is including this limit in its final rule. This limit applies to the thermal decomposition products of gum rosin soldering flux (3 to 6 percent rosin and 30 to 70 percent tin-lead solder)(Lozano and Melvin, unpublished data, as cited in ACGIH 1986/Ex. 1-3, p. 514).

A two-week exposure of guinea pigs and rats to these products at average concentrations of 0.96 mg/m³ caused reduction in rate of weight gain in male guinea pigs, abnormal liver-to-body-weight ratios in guinea pigs of both sexes, and abnormal heart-to-body-weight ratios in male rats (Industrial Bio-test Lab, Inc., as cited in ACGIH 1986/Ex. 1-3, p. 514). Lungs of the animals exposed in this same study were hyperemic.

In humans, slight bronchial irritation has been reported at 1 mg/m³ (Industrial Bio-test Laboratories, Inc. 1967, as cited in ACGIH 1986, p. 514). Several workers who were chronically exposed to levels as high as 0.15 mg/m³ had to be removed from exposure because of intractable upper respiratory tract irritation; when concentrations were kept below 0.1 mg/m³, such irritation was not reported (Christy 1965, as cited in ACGIH 1986/Ex. 1-3, p. 514). In a study designed to quantify dose-response levels for irritation in human volunteers, subjects were exposed for 15 minutes to these products at aldehyde concentrations (measured as formaldehyde, which is the best indirect measure of rosin pyrolysis products) of 0.04 to 0.2 mg/m³ (U.S. Public Health Service 1965, as cited in ACGIH 1986/Ex. 1-3, p. 514). Subjects detected the odor at 0.07 mg/m 3, and 80 percent of subjects reported moderate to severe irritation of the eyes, nose, and throat at concentrations of 0.12 mg/m³ or above. At levels below 0.05 mg/m³, fewer than 10 percent of subjects experienced irritation. Mucous membrane irritation occurred in 30 percent of subjects exposed at 0.07 mg/m³ (U.S. Public Health Service 1965, as cited in ACGIH 1986/Ex. 1-3, p. 514).

NIOSH (Ex. 8-47, Table N6B; Tr. p. 3-97 to 3-98) did not concur with OSHA’s selection of a TWA limit of 0.1 mg/m³ and recommended a ceiling limit of 0.1 ppm for a 15-minute period. In addition, NIOSH (the only commenter to the rulemaking record) considers these thermal decomposition products to be likely candidates for a separate 6(b) rulemaking.

OSHA is establishing an 8-hour TWA limit of 0.1 mg/m³, measured as formaldehyde, for rosin core solder pyrolysis products. OSHA concludes that this limit will protect employees from the significant risk of respiratory tract irritation, which is a material impairment of health, that exists at levels above the new PEL.