Neutrophil-to-lymphocyte ratio as indicator of ozone exposure

Readily measurable differences in the neutrophil/lymphocyte ratios have been demonstrated to occur in rats exposed to 3 ppm for 2 hours. The N/L ratio differences occurred within a few hours after exposure, reached a maximum within 2.5 to 12 hours, and returned to preexposure values in 24 hours. The sensitivity (3 ppm) of the response is such as to recommend the test as a simple, early indicator of overexposure to O 3. The results also showed that the response was concentration dependent, rather than exposure dependent.