Influence of alkalinization of glutaraldehyde biocidal solutions on acute toxicity, primary irritancy, and skin...

Aqueous glutaraldehyde (GA) is used at a concentration around 2% for the cold sterilization of endoscopy and dental instruments. Stock GA solution (pH 3.1-4.5) is alkalinized (pH 7.8-8.0) before use to optimize biocidal activity. The possible differential handling hazards between acidic unbuffered GA (UGA) and alkaline buffered GA (BGA) were compared for acute toxicity, primary irritancy and skin sensitizing potential using a 2.2% GA solution. Peroral LD5.0 values (with 95% confidence limits) in rats (combined sexes) were 3.45 (3.13-3.80) g/kg for UGA and 4.16 (3.13-5.52) g/kg for BGA; signs and gross pathology were similar. A 24-h occluded cutaneous application of 16.0 g/kg in the rabbit did not produce mortality; moderate skin irritancy was observed. No systemic effects occurred with UGA and only a few with BGA (unsteady gait, sluggishness, rapid breathing). Local skin irritation from a 4-h occluded contact with 0.5 ml was relatively minor and slightly more marked with BGA than UGA. Rats exposed to a statistically generated saturated vapor atmosphere for 6 h did not show any signs or gross pathology, and only slight weight loss occurred (UGA females). Rabbit eye irritation studies (0.1 ml) showed slightly more marked conjunctival reactions with BGA, but corneal injury was marked and persistent with BGA and only slight and transient with UGA. With 0.01 ml, no corneal injury occurred, but conjunctival reaction was more marked with UGA. A guinea pig maximization study showed UGA to produce a higher sensitizing index (68% at challenge, 32% at rechallenge) than BGA (30% at challenge, 5% at rechallenge). Severity indices at challenge was also higher for UGA [0.84 (24 h), 0.47 (48 h)] than BGA [0.45 (24 h), 0.18 (48 h)]. Both UGA and BGA have generally similar acute toxicity and skin irritancy; BGA has greater corneal injuring potential, and UGA has a greater skin sensitizing potential.