National Industrial Chemicals Notification and Assessment Scheme
Download 1.35 Mb.
|
- Navigate this page:
- 8.8.1Recycling process
- 8.8.2Monitoring during recycling
- 8.8.3Potential sources of exposure
- 9. Toxicokinetics and Metabolism
- 9.2Distribution
8.8RecyclingThe majority of vapour degreaser users recycle trichloroethylene either through on-site stills or off-site recyclers. From information provided by industry more than 185 tonnes of trichloroethylene in total is recycled each year at three solvent recycling plants. Other companies are known to recycle trichloroethylene, however the amounts recycled are not known. One importer and one major distributor of trichloroethylene provide recycling services to customers. The importer supplies drums to customers to hold drummed off waste. The waste is transported to a recycling plant, and recovered trichloroethylene is bought back from the recycling company. The other company has its own recycling plant and since 1988 has offered a recycling service to its customers as part of its product stewardship, which includes dissemination of literature (company manual on chlorinated solvents; MSDS; and information on exposure standards, relevant Australian Standards, and a vapour degreasing handbook); analysis of trichloroethylene samples to determine degree of contamination or identify the sources of possible problems with the vapour degreaser; and collection of contaminated trichloroethylene for recycling. Some vapour degreasers incorporate stills that operate concurrently with the vapour degreaser, collecting waste oils as the contaminated solvent passes through. Twenty-one percent of respondents to the NICNAS industry survey who used trichloroethylene in vapour degreasers indicated that they operated such stills. Waste oil and trichloroethylene mixtures collected in stills is sent to a solvent recycler. Regardless of whether vapour degreasers had stills or not, the majority of respondents sent solvent to recyclers. 8.8.1Recycling processTwo site visits were made to solvent recycling plants. One plant operates three distillation units 24 hours a day, 5 days a week and recycles trichloroethylene in batches in an enclosed system. Contents of drums are pumped into one of three enclosed distillation stills, and distillate is siphoned into covered, but not fully enclosed 200 L drums. There was no bunding around the distillation units. Distillate is checked for specific gravity, acid acceptance value and clarity. The facility is open roofed providing natural ventilation and ventilation fans run 24 hours a day. Operators wear personal protective equipment consisting of Proban overalls and hood, glasses, gloves and respirator (when cleaning out stills). Stills are cleaned out by opening doors at the bottom of the unit and raking out sludge into containers. At the other site, the contents of each drum are tested prior to recycling to check the contents. Four 200 L drums are placed on a pallet in front of one of three distillation stills and contents sucked out by vacuum pressure through steel pipes. The distillation units are situated in an open workplace with natural ventilation. Distillate drains from the still into smaller pipes leading to an enclosed vessel. There is no bunding around the stills or collection vessel. Contents of the vessel are analysed and appropriate amounts of stabiliser added. Drums are filled from the vessel. Two operators are employed at the site. Drum filling takes about ten minutes a day and operators wear gloves and organic vapour respirators. 8.8.2Monitoring during recyclingAir monitoring is conducted at one site, however no test results for trichloroethylene were made available. At another site air monitoring using Drager tubes for grab samples is done occasionally, but not on a regular basis. No results were made available. No overseas monitoring data during recycling was available. 8.8.3Potential sources of exposureDuring the recycling process, transfer of contaminated solvent from drums into distillation units and of distillate into drums is a potential source of exposure through inhalation of vapour. Cleaning sludge out of stills presents a potential source of high exposure from inhalation of vapour. Accidental spills and splashes present a further potential of inhalation and dermal exposure. Exposure during recycling is likely to be low as it involves a closed process. 9. Toxicokinetics and MetabolismNumerous reviews of trichloroethylene that have been conducted include toxicokinetics of the chemical. This section is taken mainly from the UK SIAR and IARC (1995). 9.1AbsorptionTrichloroethylene is a low molecular weight, nonpolar, highly lipophilic compound. It is absorbed readily and rapidly by inhalation, oral and dermal routes in humans and animals. Skin absorption of the vapour is negligible (Lauwerys & Hoet, 1993; Goeptar et al., 1995). In humans, between 28 to 80% of the trichloroethylene in inspired air is taken up by the lungs (Monster et al., 1979) with a high initial rate of uptake. Uptake is dependent on the rate of respiration and the trichloroethylene concentration in the inspired air. Increased workload increases the uptake of trichloroethylene in humans (Monster et al., 1979). After inhalation, 40 to 70% of the absorbed dose is metabolised. In mice, the dermal absorption rate was reported to be 7.82 g/cm2/min on application of 0.5 ml of pure trichloroethylene in a closed cell to the clipped abdominal skin of mice for 15 mins (Tsuruta, 1978). The dermal absorption rate was also investigated in hairless female guinea pigs immersed in low (0.02 - 0.1 ppm) or high (100 ppm) concentrations of trichloroethylene in aqueous solution for 70 mins. The uptake rate was found to be approximately 5.4 g/cm2/min for both the high and low concentrations (Bogen et al., 1992). 9.2DistributionAbsorbed trichloroethylene is distributed rapidly throughout the body and, in humans, the major sites of deposition appear to be body fat and liver (McConnell et al., 1975). It readily crosses the blood:brain and placental barriers. Trichloroethylene was detected in the blood of babies at birth after the mothers had received trichloroethylene anaesthesia (Laham, 1970). The blood:air partition coefficient in humans is 15 (Monster et al., 1979) and the fat:blood partition coefficient is about 700 (Steward et al., 1973; Sherwood, 1976), leading to deposition of trichloroethylene in adipose tissue. Trichloroethylene is stored in the adipose tissue for about 40 h with detectable levels even after 70 h (Fernandez et al., 1977). Directory: data -> assets -> word doc -> 0017 word doc -> Rail safety news issue 6 – October 2011 word doc -> Review of Multiple Chemical Sensitivity: Identifying word doc -> Board Endorsed October 2009 amended 13-09-11 with extra units 0017 -> Rail Safety News Edition 8, December 2012 0017 -> Commonwealth of Australia 2010 0017 -> Real-Time License Plate Localisation on fpga 0017 -> Careers network bulletin issue 6 July 16 2012 0017 -> Wiser science: Finding References inspec for Physics and Engineering 0017 -> Part A: Depth Study: The globalising world Popular culture and public policy Download 1.35 Mb. Share with your friends:
|