The Minerals Council of Australia (MCA) appreciates the opportunity to comment on selected Safe Work Australia (SWA) airborne contaminants workplace exposure standards (WESs) covering releases 2 to 14. The specific WESs commented on are limited to airborne contaminants commonly encountered in the workplace of MCA members, for which controls are provided.
As requested by SWA, the feedback focuses on comments of a technical nature regarding the toxicological information and data that the value is based upon, and measurement and analysis information provided.
The submission does not cover the practicality and cost to industry of complying with the proposed WES values. The MCA has specific concerns for the practicality and cost of implementation of some of the proposed WESs and may provide further comment on these aspects in a subsequent submission.
MCA recommends that SWA conduct a phased implementation of any new WES with prioritisation informed by the highest materiality associated with the existing WES. Further, consideration for the timing of any new WES needs to account for establishing baselines, assessing gaps and development and implementation of exposure reduction plans. This work will take time to complete as some of the substances under review are currently not routinely monitored (as the levels are well below the existing WES). It is also possible that with some agents the magnitude of reduction required under the new WES may not be technically feasible to achieve.
The key consideration from a compliance and monitoring perspective is whether the contaminant can be accurately measured at levels well below the proposed WESs, not whether the proposed WESs are measurable. When assessing whether or not accurate sampling and analytical methods are available to measure exposure to compare with or assess compliance against a recommended exposure standard, the European Commission 2017 document ‘Methodology for derivation of occupational exposure limits of chemical agents’ states that ‘Measurement techniques should be able to assess exposure at: 0.1 times the OEL for 8-hour TWA.’ The use of an action limit (e.g. half the WES) and application of a reduction factor due to extended or unusual shifts (> 8-h day / 40-hour week) would further complicate quantification of exposure concentrations against some proposed WESs. If a substance exposure concentration cannot be meaningfully compared to a WES (adjusted or otherwise) due to results being below the analytical method limit of quantitation, then the exposure data is likely to be perceived as being of little value to drive exposure controls other than the provision of respiratory protection.
The MCA questions the need for a regulatory exposure limit (WES) for a substance with irritation as the primary health effect and with warning properties. Any change in such a WES should take into consideration current toxicological data and severity of associated health outcomes. However, the MCA:
- Agrees that further study/review is required to determine an appropriate WES for both soluble and insoluble forms of aluminium, for arsenic and soluble compounds, and for fluorides, but agrees with both the arsenic and fluorides WESs as suggested
- Supports the proposed change to the WES for ammonia, benzene, cadmium and compounds (as Cd), cyanides (as CN), hydrogen cyanide (HCN – except that a short-term exposure limit (STEL) value of 5 mg/m3 is more appropriate than the proposed peak value) and nickel metal and insoluble compounds
- Suggests that the beryllium time-weighted average (TWA) WES take into account different toxicity levels depending on whether the beryllium is soluble or insoluble, as well as measurability, adopting the OSHA limit value in the interim
- Believes that the recommended WES reduction for borate compounds from 1 to 0.75 mg/m3 (as B) is not justified
- Does not support the removal of the current 12,500 ppm carbon dioxide (CO2) TWA-WES value for coal mines without further consultation
- Agrees with a reduction of the carbon monoxide (CO) TWA-WES, but believe that the ACGIH TWA of 25 ppm may be more appropriate
- Considers that a TWA-WES of 2 ppm rather than 1 ppm is probably most appropriate for carbon disulfide (CS2) potential exposures
- Considers that a TWA-WES of 0.5 ppm rather than 0.1 ppm would be sufficiently protective for chlorine exposures
- Believes that the interim TWA-WES for chromium II, III and metal (as Cr) should remain at 0.5 mg/m3 until further review is conducted
- Believes that the recommended TWA-WES for chromium VI cannot be measured using current analytical methods and that the OSHA limit value be adopted in the interim
- Prefers that the AIOH recommendations for coal tar pitch volatiles and for diesel particulate matter (DPM) be used
- Prefers that there are separate WESs for copper fume (0.05 mg/m3 respirable fraction) and copper dust and mist (0.1 mg/m3 inhalable fraction)
- Agrees with increasing the current WES for hexane to 50 ppm
- Believes that a hydrogen fluoride (HF) TWA-WES of 1 ppm and a STEL of 3 ppm would be sufficiently protective of health and irritation for the majority of workers
- Believes that a hydrogen sulfide TWA-WES of between 1 to 5 ppm and a STEL of between 5 to 10 ppm would be sufficiently protective of health and irritation for the majority of workers, depending upon measurability
- Does not agree that further study involving a review of the available carcinogenicity data for iron oxides is required (such review has already been undertaken and the determination is that iron oxides are not human carcinogens) and believe that the proposed TWA-WES value of 5 mg/m3 for the respirable fraction should be maintained
- Believes that the WES for isocyanates should be based on preventing the sensitisation of workers, and if this is the case, then the current WES may be sufficiently protective, particularly where medical surveillance is also required to detect susceptible / sensitised individuals
- Suggests that the SCOEL (2011) recommended exposure limits of 0.05 mg/m3 (respirable fraction) and 0.2 mg/m3 (inhalable fraction) would be more appropriate WESs for manganese and its compounds
- Suggests that the SCOEL (2014) recommended exposure limits of a TWA of 0.5 ppm and a STEL of 1 ppm would be more appropriate WESs for nitrogen dioxide (NO2).
The MCA also considers that in some cases where there are complexities in determining toxicity and/or assessing hazardous in-air exposure (e.g. beryllium, coal tar pitch volatiles, DPM, isocyanates), rather than depend on a ‘one-size-fits-all’ regulatory exposure limit (WES), it would be best to have an industry-specific guidance / best practice approach.
For carcinogens, exposures should be controlled to as low as reasonably practicable (ALARP) and medical surveillance should be provided. In addition, where skin absorption or hand to mouth contamination is an issue (e.g. arsenic, benzene, cadmium, carbon disulfide, carbon monoxide), and where there are validated biological indicators of exposure, then biological monitoring should be undertaken as a part of a medical surveillance program. This can also serve to check on the efficacy of controls.