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Consultation Document

Control of Substances Hazardous to Health Regulations 1999 Proposals for Maximum Exposure Limits, and Occupational Exposure Standards - responses

HSC/01/12 - Annex 3

Consultees who responded to the consultative document Cd157/00 - Proposals for Maximum Exposure Limits and Occupational Exposure Standards

HSC/01/12 - Annex 4

Summary of the substantive comments made on the domestic proposals set out in the consultative document CD 157/00, and HSE's response and recommendations presented to ACTS on 2 November 2000 (except for Flour Dust - see HSC/01/13)


ACTS/HSC Proposal:

MEL of 0.05 mg.m-3 (8 hour TWA).

Current OESs/MELs:


1 All except two of the 15 respondents who expressed a view on vanadium pentoxide agreed to the MEL proposals.

2 One employer whilst agreeing with the MEL proposals questioned whether the proposed 8 hour TWA MEL of 0.05mg.m-3 would give rise to measurement problems which would be costly for industry to resolve.

3 A consultant electrical engineer disagreed with the MEL proposals on the basis that the mutagenicity data was flimsy and might reflect the absence of metabolic protection in the tissue cultures/test system.

4 The principal response was from a company, Orbit Metallurgical Limited, which extracts vanadium and nickel compounds from power station ash. The company has a main plant, and has also recently established an experimental drying plant. The main points made by the company were as follows:

  1. it had not been consulted during the development of the RIA and as a major primary producer would have expected to have been included in the process. Inclusion of its views, that a limit of 0.05 mg.m-3 TWA MEL could result in its closure, might have influenced ACTS' conclusions. Certain data contained in HSE's assessments are inadequate and poorly researched without its input;
  2. despite its enquiries, there appears to be no evidence of new or mutagenic effects of vanadium pentoxide;
  3. initial results using personal monitoring at its plant reveal exposure levels below the proposed MEL. However, the sample size was too small to draw final conclusions, and the sampling was conducted during a period when a dryer was not operating. The company is currently assessing its long term ability to achieve the proposed limit but has not yet reached any final conclusions. A preliminary assessment is that the cost differential for a lower limit would be significant and could drive it out of business for no proven advantage. Urine sample results are not yet available;
  4. several investigations show considerable variation in the toxicity of different vanadium compounds. Its primary product is measured as vanadium pentoxide, but the chemical form of the product contains many different vanadium salts. Some methods of measuring vanadium content do not differentiate between different forms of vanadium and this should be considered in assessing the limits applied to its processing facility;
  5. it would strongly support a limit of 0.1 mg.m-3 while assessing its situation and may be in a position to support the lower limit when more workplace monitoring results become available;
  6. it expressed real concern about the impact on its business of the proposed MEL. While supporting the reduction in exposure to hazardous materials it requested additional time to assess the impact on its operations, and access to ACTS and WATCH to discuss the various issues raise by the MEL proposal.

HSE Response to paragraph 2 above

5 Estimates of vanadium pentoxide monitoring costs were set out in detail in the RIA. For a MEL of 0.05 mg.m-3 recurring annual costs were estimated between £101K and 241K. HSE does not believe that this is costly and no other respondents have raised this particular aspect of expenditure during consultation.

HSE Response to paragraph 3 above

6 Evidence is not restricted to vanadium pentoxide, but positive results have been found with a variety of vanadium salts. The evidence is detailed and shows that the mutagenicity of vanadium ions is largely, but not entirely, due to its ability to cause aneugenic changes (changes in chromosome number). The UK Committee on Carcinogenicity has advised that aneugenicity is likely to be an important mechanism for cancer development, and aneugenic changes can be found in many cancerous tissues. WATCH has reviewed the evidence on vanadium pentoxide in detail, and concluded that mutagenicity is a key concern, in addition to the respiratory tract toxicity. Furthermore, vanadium pentoxide is classified in Europe as a Category 3 Mutagen with R40.

HSE Response to paragraph 4 above

7 The information used to develop the RIA/Risk Assessment Document (RAD) was well researched and made available by companies known to HSE whose employees were exposed to vanadium pentoxide. These companies were involved in boiler/furnace cleaning and furnace demolition, catalyst refurbishment, alloy manufacture, and pigment manufacture. Together they employed some 1,100 employees. It is unfortunate but almost inevitable that some organisations are not identified and missed at the information gathering stage. However, the exclusion of one company employing 18 people does not mean that the assessment is inadequate and poorly researched.

8 HSE is arranging to send a copy of the RAD to the company which clearly indicates the mutagenic potential of vanadium pentoxide through an aneugenic mechanism. HSE will also inform the Company of the advice of the UK Committee on Carcinogenicity, WATCH's deliberations, and the European classification of a Category 3 Mutagen with R40.

9 The company is concerned about the cost of complying with the COSHH Regulations for an 8-hour TWA MEL of 0.05 mg.m-3. However, HSE believes that the main plant will not incur any costs in complying with the proposed MEL. This is based on the personal exposure data supplied by the company. Twelve exposure results (mean = 0.02 mg.m-3, range = 0.02 to 0.04 mg.m-3) were supplied and all were less than the proposed MEL. In addition, an HSE specialist inspector's report of a visit to the company in March 2000, indicated that vanadium exposure at the main plant was substantially controlled so far as is reasonably practicable. HSE cannot comment on the effects of the proposed MEL or the costs of the experimental drying plant complying with it because exposure in that plant has not yet been fully assessed. However, the specialist inspector judged that, for a MEL of 0.05 mg.m-3, adequate exposure control in that area will require great care.

10 HSE believes that the company's product comprises mainly vanadium pentoxide plus other vanadium compounds. HSE does not know the oxidation state of vanadium in the other compounds, but suspects it would be +5 because the chemical treatment of the product/impurity mixture has been the same. The proposed limit is for vanadium pentoxide, which is in the +5 oxidation state. Given that +5 forms of vanadium have been demonstrated to be mutagenic, it would seem reasonable to apply the proposed MEL for vanadium pentoxide to all the measured vanadium compounds present in the company's product. The analytical procedure does not distinguish between different vanadium compounds nor does it determine oxidation state, but produces results for vanadium expressed as mg.m-³. Also, it is not possible to extrapolate from percentage product composition to composition in air. The overall likely effect of this is that exposure results for vanadium pentoxide could be artificially high. However, HSE does not believe that anything can be done for the company in response to its request for consideration in assessing the limits applied to its processing facility, because:

  1. there is no analytical method which will distinguish vanadium pentoxide from other vanadium compounds;
  2. it is not possible to extrapolate product into air composition; and
  3. the oxidation state of any "impurities" is likely to be +5 and the health effects of inhaling these compounds is likely to be similar to those resulting from inhaling vanadium pentoxide.

11 Although the company has indicated that a MEL of 0.1 mg.m-3 (as vanadium) is acceptable, HSE notes that this is a level that has been reported to cause respiratory tract toxicity in humans. Consequently, a value lower than 0.1 mg.m-3 would seem to be more appropriate.

12 The Company has not presented any firm evidence of difficulties with complying with the proposed MEL. However, given that it did not participate in the RIA, it would seem reasonable to allow it a short time to put any further information concerning its case to HSE before the November ACTS meeting.

HSE Recommendation

13 HSE officials will provide an oral update at the November 2000 ACTS meeting about their discussions with Orbit Metallurgical to aid ACTS members' consideration of the MEL proposal.

14 As there is majority support, HSE recommends that the 8- hour TWA MEL proposal is supported by ACTS.


ACTS/HSC Proposal:

Revised OES of 200 ppm (8 hour TWA) and new OES of 400 ppm (STEL).

Current OES:

400 ppm (8 hour TWA).

15 13 of the 16 responses received supported the new OES proposals.

16 Three respondents (one employer and two trade associations) supported the arguments in the draft EH64 summary for the proposed new 8hr TWA OES of 200ppm (a reduction from the current level of 400ppm). However they supported a STEL of 600ppm derived from the "three times rule" in EH40. They disagreed with the proposed STEL of 400ppm for four reasons:

  1. there is limited data to support the proposed STEL. The only study supporting the STEL proposal was a UK human volunteer study whose findings WATCH had noted were unclear in terms of whether they identified adverse ill-health effects or mild nuisance effects;
  2. there is little data available to confidently predict that UK industry would find it easy to comply with the proposed STEL;
  3. in order to comply with the proposed STEL UK industry would have to operate more stringent engineering exposure control measures than competitors in most of Europe thereby putting it at a competitive disadvantage; and
  4. given that OES reductions are linked in many users' minds with increased toxicity, the proposed STEL might lead to unjustified pressure to substitute other solvents for ethyl acetate.

17 The employer who opposed the proposed STEL also drew HSE's attention to additional research currently being undertaken by the European Oxygenated Solvents Producers Association which included a consideration of ethyl acetate.

18 A consultant electrical engineer supported the new OES proposals but advised that currently available measurement methods in urine and breath were not good. He also questioned whether setting a low STEL, thereby negating the need for Sen and Skin notations, was a sensible approach.

HSE Response

19 WATCH held a detailed discussion of the available information from human studies on the sensory irritation effects of ethyl acetate in January 1998. While acknowledging the uncertainty of the significance of the health effects reported at a concentration of 400 ppm, WATCH concluded that a cautious interpretation of the human data was justified when setting the specific levels for the STEL OES proposals. Separately, SCOEL has reviewed this same human data and has made recommendations for health based OELs of 200 ppm (8 hour TWA) and 400 ppm (STEL). These recommendations have not yet been taken forward as IOELVs.

20 While some European Union member states currently have weaker OELs for ethyl acetate (eg. Germany), others have tighter ones (eg. Netherlands, and Sweden).

21 During the manufacture and use of ethyl acetate workers will primarily be exposed as a result of a number of short term tasks. These tasks will include, for example, taking process samples and tanker filling. Although no data is available, professional judgment suggests that exposures would not exceed the proposed STEL. These activities will, in most cases, only take a few minutes; for example, uncoupling a tanker line will take less than a minute. In addition, these activities will generally be carried out in the open air.

22 Higher short term exposures will be experienced in the printing industry. For example, operators carrying out cleaning or maintenance activities will be exposed for the duration of the activity, which will typically be longer than 15 minutes. Very little exposure data is available for such activities and therefore there is uncertainty about the level of this exposure. Ethyl acetate is a moderately volatile solvent and workers may come into close contact during activities such as cleaning, therefore exposures greater than 400 ppm 15 min TWA are possible. However, it is considered reasonably practicable to control exposure to below this value if good working practices are followed. In most cases local exhaust ventilation (LEV) will be fitted and can be used during cleaning. To further clarify this the EASE model was used to predict exposures. Where LEV is present exposures were predicted to be in the range 10 to 20 ppm 15 min TWA and where only general ventilation is used, were in the range 100 to 140 ppm 15 min TWA. In addition, there has been a general move to the use of higher boiling point solvents in the printing industry to reduce solvent exposures during such activities.

23 The STEL has no bearing on the need for a Sen and Skin notation, nor on biological monitoring.

HSE Recommendation

24 In view of the majority support, and the scientific evidence supported by WATCH, HSE recommends that the both the revised 8 hour TWA OES and the new STEL OES proposals are supported by ACTS.


ACTS/HSC Proposal:

Revised OESs of 5 ppm (8 hour TWA) and 10 ppm (STEL).

Current OESs:

10 ppm (8 hour TWA) and 15 ppm (STEL).

25 16 of the 17 responses received on hydrogen sulphide supported the new OES proposals. One trade association disagreed with the proposals on the grounds that they are not reasonably practicable in the UK wastewater industry. This association argued that the resources necessary to control hydrogen sulphide exposure to the new OES greatly outweigh any proven potential reduction in risk to human health. The association suggested that the OESs should remain unchanged pending further research to assess the link between low level exposure and ill-health effects.

26 One trade association supported the proposals but indicated that they might result in significant costs to industry arising from knock-on changes in environmental protection legislation (see paragraphs 11(ii) and 12(iv-(v) of main paper).

27 A consultant electrical engineer supported the OES proposals but suggested that the NOAEL should be substantiated by human rather than animal data as soon as possible.

HSE Response

28 In the wastewater industry, hydrogen sulphide is produced following the anaerobic breakdown of waste material for example, during effluent and sewage treatment. Under normal working conditions personal exposure should not exceed the proposed OESs of 5 ppm 8-hour TWA and 10 ppm 15 minute STEL. However, it is expected that in some situations in particular during work in underground sewers and manholes (ie. confined spaces) that personal exposure will exceed the proposed OESs. For such work, the wastewater industry has indicated that they use appropriately placed gas monitors to detect high gas excursions and have instigated steps to deal with them when they occur. These include the use of forced ventilation, the wearing of suitable respiratory protective equipment etc. As most of the risk management strategies for controlling hydrogen sulphide are already in place, HSE considers that it should be reasonably practicable for the industry to control exposure to the gas to below 5 ppm 8-hour TWA without significant additional cost.

29 WATCH proposed to reduce the current OESs for Hydrogen Sulphide primarily on the basis of findings from a series of human volunteer studies which demonstrated some potentially adverse effects on aerobic metabolism following relatively short exposures to 10 ppm during vigorous exercise. WATCH acknowledged that there was some uncertainty regarding the toxicological and health significance of these changes but they considered that the evidence for biological effects at 10 ppm caused some concerns over whether the current 8-hour TWA OES of 10 ppm was sufficiently protective to health. On the basis of this human data, together with an indication from an occupational hygiene survey that lower OESs were practical across industry, WATCH proposed the tighter OESs detailed in CD157/00.

HSE Recommendation

30 In view of the majority support, and the scientific evidence supported by WATCH, HSE recommends that the 8 hour TWA and the STEL OES proposals are supported by ACTS.


ACTS/HSC Proposal:

Withdraw the three separate OESs and develop a single MEL.

Current OESs:

Manganese & its inorganic compounds - 5 mg.m-3 (8 hour TWA), Manganese Fume - 1 mg.m-3 (8 hour TWA) and 3 mg.m-3 (STEL), Trimanganese Tetraoxide - 1 mg.m-3 (8 hour TWA).

31 13 of the 15 responses received on manganese and its inorganic compounds were in favour of the proposal to withdraw the OES and develop a MEL.

32 Two respondents opposed the proposal on the grounds that the OES should not be withdrawn until a MEL is in place (see paragraphs 11(i) and 12(i)-(iii) of main paper).

33 One trade association, while supportive of the proposal to develop a MEL for manganese and its inorganic compounds, indicated that a MEL might have significant implications for the UK manganese steel industry depending on the level set. A MEL at 5 mg.m-3 (8 hour TWA) would not cause problems. However, a tighter limit might do. They advised that, disregarding Respiratory Protective Equipment, exposures above 1 mg.m-3 (the current OES for manganese) had been measured at furnaces melting manganese steel. They requested an indication from HSE of the likely MEL.

HSE Response

34 HSE officials have spoken to the trade association and have explained that, subject to ACTS/HSC approving the development of a MEL, HSE will ensure that the association is kept informed of the MEL proposals as they are progressed.

HSE Recommendation

35 As there is majority support for this proposal HSE recommends ACTS supports the withdrawal of the three OESs for manganese and its inorganic compounds, manganese fume, and manganese tetraoxide, and the development of a single MEL for these substances.

Updated 2009-05-28