Tolerance and cross-tolerance development to atmospheric pollutants ketene and ozone

¹ U.S. Department of Health, Education, and Welfare, Public Health Service, Bureau of State Health Services, Occupational Health Program, Cincinnati, Ohio

Tolerance to oxidants, that is remarkable both in its rapidity of onset and its high degree of protectiveness, has been demonstrated in mice exposed briefly to ketene. Exposure of mice to concentrations of ketene in excess of 5 ppm for 10 minutes protected mice 3–14 days later against otherwise lethal exposures. Similarly, a cross-tolerance was demonstrated for ozone; a pre-exposure to ketene protected mice against lethal concentrations of ozone. Ozone likewise produced a cross-tolerance for lethal exposures to ketene. The 10-day LC₅₀, which is the concentration required to produce a 50% kill in 10 days by a 10-minute exposure of mice to ketene, approximates 17 ppm (v/v), with production of pulmonary edema. Pulmonary edema of lesser degrees resulted at lower exposure concentrations, but was not present to a significant extent in mice exposed to lethal concentrations of the respiratory oxidants, provided the mice had first received a tolerance-producing pre-exposure of the respiratory oxidant.