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2 TCDD: Physicochemical Properties and Health Guidelines
Pages 16-26

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From page 16...
... can serve as a chemical "signature" of these herbicides used by the military in Vietnam. After the Vietnam War, analyses of residual herbicide stocks found that contamination by the TCDD congener specifically ranged from less than 0.05 parts per million (ppm)
From page 17...
... , such as TCDD, are in constant flux around equilibrium. Prior to reviewing past interpretations of the available sampling data, it is worthwhile to explore the theoretical distribution of TCDD and other SVOCs in the indoor environment and relate this to the exposure potential for AF Reserve personnel who served on C-123s that had formerly sprayed defoliants in Vietnam.
From page 18...
... From these concepts we can assume that a satisfactory sampling scheme would involve multiple media types (such as air, residue or films, and dust)
From page 19...
... The recognition that most of the toxicity of PCBs and also furans results from specific congeners that share the AH-receptor mechanism of action with TCDD with a lower degree of potency has permitted development of a unified measure of toxic potency for dioxins, PCBs, and furans. Exposure standards for these chemicals have been set in terms of TEQs, which are the summed TEFs weighted by the measured amount of their associated congener in a particular analyzed sample.
From page 20...
... Technical Guide 312     3.5 (CHPPM, 2009) World Trade Center 1 2 Working Group (WTC, 2003)
From page 21...
... TCDD: PHYSICOCHEMICAL PROPERTIES AND HEALTH GUIDELINES 21 Routes Included in Population Targeted Guideline Lifetime Risk by Guideline Exposure Duration (source-mode of entry) 4 × 10−4 to 70-kg adult 40-yr working lifetime Air: inhalation 4 × 10−3 cancer < 2 × 10−4 cancer Adult office worker 30 yrs Air: inhalation; Surface residues: ingestion, inhalation 1 × 10−6 to 5 × 10−5 65–70-kg adult Working lifetime cancer office worker 9 × 10−8 to 50-kg adult office 250 days/yr, 30 years Air: inhalation; 2 × 10−4 cancer worker Surface residues: ingestion, inhalation < 1 × 10−6 cancer Adult office worker Working lifetime 65-kg adult office Working lifetime worker 1 × 10−6 cancer Long-term office   Surface residues: workers ingestion, dermal, and inhalation 1 × 10−4 cancer 70-kg adult Residence for 30 yrs, Air: inhalation; 365 days/yr, 24 hr/day Settled dust: ingestion, dermal General public  Acute(< 15 days)
From page 22...
... 10   NOTES: ADI, acceptable daily intake; ATSDR, Agency for Toxic Substances and Disease Registry; CSF, cancer slope factor; EPA, Environmental Protection Agency; JECFA, Joint FAO/WHO Expert Committee on Food Additives; kg-time, body weight of exposed individual over specified time period; LADD, lifetime average daily dose; LOAEL, lowest-observed-adverse-effect level; MRL, minimal risk level (daily human exposure that is likely to be without appreciable risk of adverse, noncancer effects over a specified duration of exposure -- ATSDR) ; NOEL, no-observed-effect level; NRC, N ­ ational Research Council; OEL, occupational exposure limit; PTI, provisional tolerable intake; RfD, ­ reference dose (estimate with uncertainty spanning about an order of magnitude of a daily exposure likely to be without appreciable risk of deleterious noncancer effects during a lifetime)
From page 23...
... TCDD: PHYSICOCHEMICAL PROPERTIES AND HEALTH GUIDELINES 23 Routes Included in Population Targeted Guideline Lifetime Risk by Guideline Exposure Duration (source-mode of entry)   General public  Cumulative over extended Oral period General public  Chronic  Oral    General public  Chronic Oral    General public  Lifetime Oral   General public  Chronic  Oral   General public  Chronic  Oral   General public  Lifetime Oral and inhalation   General public Continuous exposure over Oral lifetime General public Lifetime
From page 24...
... . Most of these surface contamination and air guidelines were derived for protection of office workers working in TCDD-contaminated buildings, and utilize exposure scenarios and assumptions pertaining to work practices of office workers, such as breathing rates, rate of contact of hands and arms with contaminated surfaces, percent of contaminant transferred to hands or arms after surface
From page 25...
... Because fires involving PCB-containing equipment can release TCDD and PCB-related combustion products into the environment in toxicologically relevant concentrations, such fires are the basis for numerous federal and state regulatory and other actions designed to reduce human harm. EPA's "Transformer Rule" under Toxic Substance Control Act (40 Code of Federal Regulations, Part 761)
From page 26...
... The screening level assumes exposure to contaminated surfaces through dermal contact and absorption, incidental ingestion by hand-to-mouth behaviors, and inhalation through breathing resuspended particulates. The upper bound cancer risk is set to 1 × 10−6 for a 70-kg office worker over a 10-year exposure duration.


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