Pesticide Toxicity PPM (parts per million)-1 oz in 62,500 Ibs or 1 tbs in 3,906 gal PPB (parts per billion)-1000 times less than ppm 1 tbs in 3,906,000 gal Half-life time for 1/2 of initial concentration to be degraded Volatility ability of a liquid to evaporatePesticide Toxicity PPM (parts per million) - 1 oz in 62,500 lbs or 1 tbs in 3,906 gal PPB (parts per billion) - 1000 times less than ppm - 1 tbs in 3,906,000 gal Half-life - time for 1/2 of initial concentration to be degraded Volatility - ability of a liquid to evaporate