This chapter develops an effective toxicity factor (ETF) in units of doses/capita-pound that can then be used to evaluate the relative overall toxic impacts of the various Toxics Release Inventory chemical releases. A toxicity unit of 1 means that the pounds of a chemical released in a given year coupled with the quantified ETF of the chemical has reached the toxicity threshold if distributed evenly over the population of the United States (US). The chapter presents the proposed ETFs for TRI chemicals. The ETFs were derived by multiplying together each of the following factors: toxicity factor, mobility factor, persistence factor, and bioconcentration adjustment factor. The chapter also shows the 2007 TRI release data ranked by pounds released and includes the calculated TUs. TU was calculated by multiplying the ETF by the amount released in pounds and represents the estimated toxicity impact per capita of the release of that chemical.