External considerations: Reduction of exposure or accessibility ❖ A. Properties related to environmental distribution/dispersion ❖ 1. Volatility/density/melting point ❖ 2. Water solubility ❖ 3. Persistence/biodegradation ❖ a. oxidation, b. hydrolysis, ❖ c. microbial degradation ❖ 4. Conversion to biologically active substances ❖ 5. Conversion to biologically inactive substances
External considerations: Reduction of exposure or accessibility ❖ A. Properties related to environmental distribution/dispersion ❖ 1. Volatility/density/melting point ❖ 2. Water solubility ❖ 3. Persistence/biodegradation ❖ a. oxidation, b. hydrolysis, ❖ c. microbial degradation ❖ 4. Conversion to biologically active substances ❖ 5. Conversion to biologically inactive substances
❖ B. Properties related to uptake by organisms ❖ 1. Volatility ❖ 2. Lipophilicity（亲油性） ❖ 3. Molecular size ❖ 4. Degradation ❖ a. hydrolysis（水解）, b. Effect of pH, ❖ c. susceptibility to digestive enzymes （消化酶） External considerations: Reduction of exposure or accessibility
❖ B. Properties related to uptake by organisms ❖ 1. Volatility ❖ 2. Lipophilicity（亲油性） ❖ 3. Molecular size ❖ 4. Degradation ❖ a. hydrolysis（水解）, b. Effect of pH, ❖ c. susceptibility to digestive enzymes （消化酶） External considerations: Reduction of exposure or accessibility
❖ C. Consideration of routes of absorption by man, animals or aquatic life ❖ 1. Skin/eyes ❖ 2. Lungs ❖ 3. Gastrointestinal tract（消化系统） ❖ 4. Gills(鳃) or other specific routes External considerations: Reduction of exposure or accessibility
❖ C. Consideration of routes of absorption by man, animals or aquatic life ❖ 1. Skin/eyes ❖ 2. Lungs ❖ 3. Gastrointestinal tract（消化系统） ❖ 4. Gills(鳃) or other specific routes External considerations: Reduction of exposure or accessibility
❖ D. Reduction/elimination of impurities ❖ 1. Generation of impurities of different chemical classes ❖ 2. Presence of toxic homologs（同系物） ❖ 3. Presence of geometric, conformational or stereoisomers(几何、构象及光学异构体) External considerations: Reduction of exposure or accessibility
❖ D. Reduction/elimination of impurities ❖ 1. Generation of impurities of different chemical classes ❖ 2. Presence of toxic homologs（同系物） ❖ 3. Presence of geometric, conformational or stereoisomers(几何、构象及光学异构体) External considerations: Reduction of exposure or accessibility
❖ Bioaccumulation（生物集聚）or ❖ Bio-magnification (生物放大): ❖ It refers to the increase of tissue concentration of a chemical as it progresses up the food chain. External considerations:
❖ Bioaccumulation（生物集聚）or ❖ Bio-magnification (生物放大): ❖ It refers to the increase of tissue concentration of a chemical as it progresses up the food chain. External considerations: