Acceptable daily intake 2 ,3,7 ,8-TCDD

Symptoms of exposure Skin irritation. May also cause eye, nose, and throat irritation (NIOSH, 1987). An acceptable daily intake reported for humans is 0.03 mg/kg body weight provided the product contains <0.01 mg TCDD/kg 2,4,5-T (Worthing and Hance, 1991). 

There is no reference dose for dioxins. The acceptable daily intake is l-10pgkg day . A threshold limit value for TCDD has not been established. 

The recommended daily intake values as estimated by the United States Environmental Protection Agency (EPA) (4) and the Centers for Disease Control (CDC) (5,6) have been used for the present calculations. For the EPA the "Acceptable Daily Intake" (ADI) for 2,3,7,8-TCDD is 1 x 10" g/kg/day. This value is based on the lowest-observed-adverse-effect-level (LOAEL) of 1 X 10 g/kg/day for a reproductive effect in rats (7,8), a 10-fold uncertainty factor because a LOAEL is used as the basis of the calculation rather than a no-observed adverse effect level (NOAEL), and an additional uncertainty factor of 100 based on the existence of lifetime animal studies and lack of knowledge of the effects in man. (4). For a 10" (1/1,000,000) cancer risk, the EPA has estimated a 95% lower-limit criteria for a lifetime intake of... 

As early as 1981, Rodricks (72) suggested that in light of TCDD s lack of genotoxicity, the safety factor approach would be appropriate for setting an acceptable daily intake (ADI) using this approach, he calculated a 10 pg/kg/day figure. More recently, the Province of Ontario and several Western European countries, as well as European scientists, have estimated TCDD risk to humans that Is significantly less than EPA s estimate. 

EPA uses the 0.006 pg/kg/day 2,3,7,8 - TCDD equivalents although several states have accepted 2.0 pg/kg/day. European countries us acceptable daily intake levels ranging from 1.0 pg/kg/day to 10 pg/kg/day. 

There have been few recent advances in the toxicological literature as to the hazards of 2,3,7,8- TCDD or its equivalents. At a recent European conference reported human pharmocokinetic studies indicate the biological half-life of 2,3,7,8- TCDD has been calculated to be on the order of five years. Such conclusions were interpreted as justifying the rethinking of the reduction of acceptable daily intake levels. TCDF data on the biological fate of PCDF s support the five year biological half-life theory. 

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