SAS probit analysis for cadmium mortality

Abstract

In the quantitation of heavy metal effectiveness it is useful to compute the median lethal dose (LD 50) to the exposed population. The computerized Statistical Analysis System (SAS) of probit analysis is particularly useful in analyzing dose-response data because it is more accurate than the graphical methods currently in use and, in addition, provides fiducial limits with its estimates. Acute and chronic cadmium mortalities of young adult male and female Sprague-Dawley rats were determined by the SAS probit analysis. When male and female rats were administered comparable doses of cadmium chloride, based on individual body weights, males were more susceptible. A plausible explanation for this greater sensitivity of males to the heavy metal is testicular necrosis. The acute LD 50 (30 days) value for males was 5.99 mg Cd/kg body wt, with 95% fiducial limits of 4.71-7.54 mg Cd/kg body wt, as compared to 7.13 (5.18-8.85) mg Cd/kg body wt for females. When multiple (chronic doses of cadmium were injected, LD 50 (30 days) values were 4.25 (3.42-5.05) mg Cd/kg body wt and 5.14 (4.42-5.92) mg Cd/kg body wt for males and females, respectively. Values calculated 30 days after the last injection (at Day 60) were 3.38 (2.61-4.05) mg Cd/kg body wt and 4.65 (4.00–5.25) mg Cd/kg body wt for males and females, respectively. Chronic LD values indicate an increase in effectiveness of dose as time of injections was protracted.