National Industrial Chemicals Notification and Assessment Scheme
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- 17.4Exposure standard
- 17.5Public health protection
- Recommendation 16
- 17.6Environmental protection
- 17.7Further studies
- 18.Secondary Notification
Recommendation 14:Workers potentially exposed to trichloroethylene should be provided with training in the safe handling of the chemical. Workers should be aware of the health hazards of the chemical. For trichloroethylene, the training program should address those aspects detailed below.
Training should be given to the workers at induction and repeated at regular intervals to reinforce the information. Training and education needs for workers should be reviewed on a regular basis. Guidelines for the induction and training of workers are provided in the NOHSC National Model Regulations and Code of Practice for the Control of Hazardous Substances (NOHSC, 1994) 17.4Exposure standardRecommendation 15:It is recommended to NOHSC that the present occupational exposure standard for trichloroethylene of 50 ppm TWA be reviewed noting: the critical effect is renal toxicity; the inhalation NOAEL for renal toxicity is 100 ppm, the LOAEL is 300 ppm. These values do not include a margin of exposure (uncertainty factor); a classification of carcinogen Category 2 has been recommended; a classification of mutagen Category 3 has been recommended; and trichloroethylene is readily absorbed through the skin. recent monitoring data indicate that exposures around the current occupational exposure standard (TWA) or even higher are occurring at workplaces; and the monitoring data included and other relevant information included in this assessment report. 17.5Public health protectionTrichloroethylene is not expected to present a significant hazard to public health provided that consumer products containing trichloroethylene are labelled in accordance with the requirements of the Standard for the Uniform Scheduling of Drugs and Poisons (Australian Health Ministers' Advisory Council, 1997) and the instructions on the labels strictly adhered to (See Section 17.3.2). During preparation of this report, it was noted that the lowest oral LD50 value for trichloroethylene in rats is 4900 mg/kg bw (IPCS (International Programme on Chemical Safety), 1985). Recommendation 16:It is therefore recommended that the T-value for trichloroethylene in Appendix E Part 2 of the SUSDP, be revised from 715 to 490. There are no objections to the continued use of trichloroethylene in the indicated applications, subject to the above provisions. If the conditions of use are varied, greater exposure of the public to the product may occur. In such circumstances, further information may be required to assess the hazards to public health.
Recommendation 17:Solvents such as trichloroethylene should not be allowed to contaminate either surface water or ground water. The residue obtained following distillation of the used solvent, in the form of a highly concentrated final waste, should be disposed of by a licensed contractor. 17.7Further studiesThere is a large body of literature on trichloroethylene, however, some gaps identified in the database for trichloroethylene are: the mechanism of action of carcinogenicity in kidneys (to elucidate the relevance of these tumours to humans); methodical studies with ‘pure’ trichloroethylene in systems that detect a point mutation end point; information to estimate the skin absorption rate of trichloroethylene in humans (to provide a better estimate of skin absorption); information relating metabolism of trichloroethylene in humans to that in rats and mice (to determine the most appropriate model for humans. Differences in metabolism across species may account for the different outcomes in cancer studies in rats and mice. Additionally saturation of metabolism at high doses is postulated to occur in humans but sufficient data is lacking); and studies on the developmental neurotoxicity of trichloroethylene in animals (as a series of oral studies from a laboratory have indicated that trichloroethylene may produce developmental neurotoxicity); data on the fate and persistence of trichloroethylene released into Australian groundwater, sediments and subsurface soils, including any sites contaminated with this substance, other than Orica Botany, would enable a more complete evaluation of the potential environmental hazard of trichloroethylene in Australia.
In the case of trichloroethylene, a secondary notification may be required if significant new information about its health and/or environmental effects becomes available, for example new data on the mutagenic or reproductive effects of trichloroethylene. Notification will also be required if trichloroethylene is used in wool scouring or any other new use resulting in a significant increase in the quantities imported into Australia. APPENDIX 1 OCCUPATIONAL EXPOSURE CALCULATIONS
A total internal dose, (D) that is an estimated human dose, is the sum of the doses resulting from absorption of vapours (Dv) and dermal absorption of liquid (Ddl). D = Dv + Ddl Vapour absorption (Dv) comprises of inhalation absorption across the lungs (Div) plus dermal absorption of vapours (Ddv). Dv = Div + Ddv However, as dermal absorption of trichloroethylene vapour is negligible, only inhalation absorption is considered in this assessment. Therefore, for trichloroethylene D = Div + Ddl Exposure to vapours The dose arising from the inhalation of vapours (Div) is as follows: Div in=CREB mg/kg/day BW Where C=concentration of substance in air (mg/m3) R=inhalation rate (m3/h) E=exposure duration = h/day days/yr 365 days/yr B=bioavailability of vapours across the lungs (1=100%) BW=average body weight of worker (kg) Bioavailability (B) is the proportion of inhaled substance absorbed through the lungs. After inhalation of trichloroethylene, 40 to 70% of the administered dose is metabolised with the rest being exhaled (IARC, 1995). The default value used often in international assessments is 0.75 (75%) and as the values for trichlorethylene are similar, a value of 0.75 was used for this assessment. For consistency with international assessments, a value of 1.3 m3/h was used for the inhalation rate (R) for occupational exposure during light work activities (OECD, 1993; European Commission, 1994) and a value of 70 kg was used for body weight (BW). The exposure duration (E), that workers may be potentially exposed to trichloroethylene, during the various activities were obtained from responses to questionnaires. Exposure to liquid The daily total dose from liquid exposure (Ddl) is calculated as follows: Ddl = W x S x A x E x F mg/kg/day BW
S = skin absorption rate (mg/cm2/h) A = skin surface area exposed (cm2) E = exposure duration = h/day x days/yr 365 days/yr F = skin contact time (as fraction of exposure duration, e.g. 0.2 for 20% of time). BW = average body weight of worker (kg) For skin absorption rate, no human data either in vivo or in vitro using human tissue were available. The skin absorption rate (0.32 mg/cm2/h) used in the calculations was derived from an experiment in hairless guinea pigs (Bogen et al, 1992)(see Section 9). For skin surface area (A) standard area estimates for the adult male include the following standard US EPA values (in cm2): arms 2280 upper arms 1430 forearms 1140 hands 840 head 1180
Liquid trichloroethylene can be in contact with the skin for various fractions (F) of the exposure duration (E) so skin contact can be extensive, intermittent or incidental. Extensive dermal exposure is taken as continuous contact (F=1) with the skin. Taking into account assumptions made in the UK EASE* (Estimation and Assessment of Substance Exposure) model for dermal exposure, intermittent exposure is taken as being skin contact for 20% of the time (F=2), and incidental exposure as skin contact for 1% of the time (F=0.01). * The EASE model is the second version of the knowledge based electronic system in development by the UK Health and Safety Executive (HSE), and was formerly called EES (Exposure Expert System).
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