Pubh 6011 Final 102 Correctly Answered Questions Latest Update

explain typical water treatment processes in developed countries including disinfection by-products {Ans: 1. Screen, usually surface water only 2. Flocculation / coagulation: chemicals that are used to clump fine particles together. Particles stick and grow big enough and eventually settle out. 3. Sedimentation: all the particles stuck to flock are removed through gravity 4. filtration: activated charcoal takes chemicals and other things out of water by binding to them 5. disinfection 6. storage 7. Distribution of water}Dose-response evaluation {Ans: *an attempt to quantitatively determine the relationship between exposure to a toxicant and disease.}Explain the difference between 8-hour PELs/TLVs, STELs/Ceiling Limits and IDLH {Ans: ○ We regulate workplace chemicals by setting PELs or TLVs - limit set to protect adult worker exposed 40 hours per week for 40 yrs ■OSHA - PELs ■ACGIH - TLVs ■TLV: threshold limit values...ACGIH limit, so scientifically sound but not legally enforceable ■PEL: permissible exposure limit: OSHA value ● Both TLVs and PELs use either ceiling limits (max concentration allowed...denoted by c next to number) or 8 hour time weighted average (used for most chemicals with long-term toxicities) ■Most shifts are 8 hours, avg exposure is compared to