ACUTE PERCUTANEOUS SYSTEMIC TOXICITY OF CYANIDES

The acute percutaneous systemic toxicity of hydrogen (HCN), sodium (NaCN), and potassium cyanides (KCN) was investigated in female albino rabbits. LD(50) values (with 95% confidence limits), in mmol/kg, for solutions applied to intact skin were 0.260 (0.238-0.278) for HCN, 0.299 (0.282-0.315) for NaCN, and 0.344 (0.315-0.369) for KCN. The corresponding values for solutions applied to abraded skin were 0.087 (0.076-0.097), 0.231 (0.188-0.259), and 0.220 (0.204-0.233). NaCN powder applied at 200 mg/kg to dry intact skin did not produce death or signs, and applied to intact moist skin it gave an LD(50) of 0.243 (0.152-0.388) mmol/kg and NaCN powder applied to abraded skin gave an LD(50) of 0.151 (0.137-0.160) mmol/kg. For each application condition there was a wide range of times to onset of signs and times to death. Mean times to death were shortest with NaCN powder applied to abraded skin (44.5 min) and longest with NaCN solution applied to intact skin (252.1 min). Signs, seen mainly in animals that died, included tremors, retrocolic spasms, convulsions, abnormal breathing patterns, and prostration. In a follow-up investigation, cyanide was measured in blood, serum, and various tissues removed immediately after death following epicutaneous dosing with solutions of HCN, NaCN, or KCN to intact rabbit skin at 35 mg CN/kg (i.e., 3.9-5.3 x LD(50)). High cyanide concentrations were measured in whole blood and serum from all groups, and detected analytically in heart, liver, kidney, spleen, lung, brain, and spinal cord. Highest average tissue concentrations were measured in heart, kidney, brain, and lung. Lowest individual concentrations were in liver. These results indicate a potential for acute lethal toxicity by single sustained contact of cyanide solutions with intact skin, or NaCN powder on moist skin. Lethal toxicity (as LD(50)) is enhanced by skin injury. There are clear indications for the use of protective measures when handling cyanide.