Health and Safety
Executive / Commission
Regulatory Impact Assessments: Chemicals
Issue and Objective
Chlorobenzene is a colourless liquid with a boiling point of 132 C at 101.3 Kpa and vapour pressure of 1.665 KPa at 25 C. It has an odour threshold of 0.21 to 0.68 ppm, resembling almonds, benzene and/or moth balls.
Chlorobenzene is included in a European Commission Directive on Indicative Occupational Exposure Limit Values (IOELV). The IOELVs are 10 ppm as an 8-hour TWA, and 20 ppm as a 15-minute STEL. Member states are required to have set national occupational exposure limits for chlorobenzene that take into account the IOELVs by 31 December 2001. Chlorobenzene currently has an Occupational Exposure Standard (OES) of 50 ppm 8-hour TWA (but no STEL). ACTS has agreed that this OES should be withdrawn, and a proposal to this effect is included in a Consultative Document CD157 issued in May 2000. The ultimate objective is to replace the OES with a Maximum Exposure Limit (MEL). This document will inform ACTS as to the financial consequences of this procedure.
Evidence from studies in animals indicates that bone-marrow and liver are the key target organs for the toxic effects of chlorobenzene. There is an additional concern for possible genotoxic effects. Chlorobenzene also produces kidney damage but only at exposure concentrations greater than those required to cause effects on the bone-marrow and liver.
The available animal information does not permit the identification of a no-effect level for effects on the bone-marrow. The lowest exposure concentration at which effects on the bone-marrow have been observed is 21 ppm, which is the lowest airborne concentration tested. Similarly, it is not possible to identify a clear no-effect level for the effects of chlorobenzene on the liver.
There is evidence from a study conducted in vitro that chlorobenzene is genotoxic. However, there are no adequate studies to confirm whether this property may be expressed in vivo.
In relation to the value for the 8-hour TWA MEL, given the evidence for damage to the bone-marrow at 21 ppm, a value substantially below this concentration would seem appropriate to reduce the risk of bone marrow changes in workers. However, there are insufficient data to reliably quantify what the risk might be at any particular level of exposure below 21 ppm.
The Indicative Occupational Exposure Limit Values (IOELVs) for chlorobenzene include values for a STEL as well as an 8-hour TWA. The STEL recommendation was aimed at controlling peaks in exposure which might result in irritation. A human volunteer study claimed irritation at 60 ppm (7-hours exposure), whereas no irritancy was reported at 12 ppm. Hence, a value for a STEL MEL of 12 ppm or below would be suitable. Given that chlorobenzene is predicted to be well absorbed across the skin, and could thereby contribute to systemic toxicity, a 'Sk' notation would be required in relation to any MEL that is established.
Exposure to hazard and methods of control
Repackaging and distribution. There are a few companies involved with repackaging and distribution of chlorobenzene. About five companies import and distribute chlorobenzene in the UK, involving transfer between storage vessels and road tankers or drums. In addition, there are between five and ten companies who repackage the chlorobenzene in small containers, typically into 2.5 litre Winchesters or smaller, for supply to laboratories.
Occupational exposure data were not received from companies repackaging chlorobenzene. To determine this exposure modelling was carried out using the EASE model. Workers may carry out repackaging for a full 8-hour shift. Assuming that LEV is in place to control exposure the EASE scenario that best describes this exposure is non-dispersive with LEV. This results in an EASE prediction of 1 to 3 ppm 8-hour TWA.
Chemical plants. Occupational exposure for workers on chemical plants will be intermittent and as a result of tasks where the closed system is breached, for example, material sampling and tanker unloading. Consequently 8-hour TWA exposure arises from a series of short term exposures. Systems are adopted that minimise the potential for the release of chlorobenzene vapour during breaches of the plant. Occupational exposure may also occur from fugitive emissions, for example, leaks from pump seals.
Occupational exposure to chlorobenzene during its use as a process solvent will only occur at the earlier stages of the process. Similarly if chlorobenzene is being used as a chemical intermediate exposure will again not occur once the product reaction has been completed. Product sampling and tanker filling will not involve exposure to chlorobenzene, but the substance being produced on the plant. Therefore exposure will only occur during:
Occupational exposure data has been collected from UK industry as part of the review of the OES for chlorobenzene. Personal air sampling results at one site were up to 6 ppm 8 hour TWA, with 83% of results less than 1 ppm 8 hour TWA. At another site the highest personal air sampling result was 0.2 ppm 8-hour TWA. Published data showed higher exposures: Kusters and Lauwerys (1990), <0.05 to 106 ppm (median 1.2 ppm) at a Belgium plant; and Kumagai and Matsunaga (1994), 0.2 to 38.5 ppm 8-hour TWA for Japanese workers. The Kusters 1990 survey included a total of 251 workers carrying out maintenance work and the figure of 106 ppm was the only result greater than 50 ppm. The highest exposure data received was from a company who used chlorobenzene until the end of 1998 as a chemical intermediate. Exposures were up to 329 ppm for the duration of the task (1 to 2 hours) and up to 59 ppm when time-weighted over the 8 hour shift. These higher exposures were as a result of operators manually shoveling product wet with chlorobenzene on to oven trays or scraping wet product from the inside of centrifuges. LEV was provided during the latter operation and operators wore air fed RPE. This process ceased at the end of 1998.
Further results have been received as part of this regulatory impact assessment. Thirty eight personal air sampling results were received, thirty seven of which were less than 1 ppm 8-hour TWA. The one exception was at 3.2 ppm 8-hour TWA.
Short term exposure to chlorobenzene during its use as a chemical intermediate as predicted using the EASE model.
Table 1: Short-term exposure data (EASE modelled)
| Activity | Control | 15-min TWA exposure (ppm) |
| sampling | 4.6 to 6.7 | |
| tanker unloading | vapour return on storage vessel | 1.3 to 3.3 |
| no vapour return | 20 to 50 | |
| vessel charging from a drum | LEV / negative pressure | 1 to 3 |
| no ventilation control | 70 to 100 |
Laboratory use. The number of laboratories handling chlorobenzene could be quite large, although it is likely that in case they will only be handling small volumes on an infrequent basis. They tend to categorise their use of hazardous chemicals, with those deemed to present a greater risk to health used in fume cupboards. Those companies contacted reported that chlorobenzene is handled in fume cupboards.
Adhesives. Chlorobenzene also has limited use in adhesives, although it was not possible to identify the exact nature of the this use, the number of companies using it or the likely exposures. The manufacturer of this chlorobenzene based adhesives felt that due to commercial pressures and confidentiality issues, that they were not able to assist HSE with this regulatory impact assessment. Therefore they did not provide HSE with any details about the nature of this use, levels of exposure or costs that their customers may have to incur with the implementation of a new MEL. It was also not possible to identify any companies using adhesives containing chlorobenzene.
Options considered
HSE has undertaken a Regulatory Impact Assessment for a MEL at various levels of exposure.
The following levels were chosen for comparison.
Consultation with industry with reference to a short-term exposure limit for chlorobenzene was carried out during a second exercise. This asked companies to comment on the initial findings for the above options and the compliance costs for a short term exposure limit at three times the above values. The results of this second exercise are reported in paragraph 35.
Information sources
Information for this RIA was collected via a survey of the industries affected. Questionnaires, asking for information on processes, exposure patterns and potential costings were sent to the following:
A total of about 20 questionnaires were sent out to the above sectors. This concentrated mainly on the chemical industry, although some were sent to companies representing laboratory users. Visits were made to two users of chlorobenzene as part of the original occupational hygiene assessment. Trade associations were not contacted as no particularly relevant organisations were identified.
The above companies and any further businesses identified were sent a first draft of the regulatory impact assessment for comment, which highlighted the initial findings.
Technical assumptions
All costs are calculated in 1999/2000 prices over a ten year period11. The base year for appraisal is year 1999/2000. Details of the actual costings are described below.
The companies who returned the questionnaires reported that there had been no cases of ill health that they associated with exposure to chlorobenzene on their sites.
As explained in the risk assessment section, if the chlorobenzene is genotoxic in vivo, then reducing exposure will reduce the level of risk of genotoxic damage. However, we cannot quantify any aspect of this.
Furthermore, the information provided by the companies contacted suggests that exposure above 1 ppm is currently rare, and therefore the benefits from setting a MEL at any of the proposed levels are likely to be very small.
Business sectors affected
For the purposes of this document, the business sectors affected were divided into different categories. These categories are not mutually exclusive and the different trade associations who returned questionnaires did not always fit easily into one or other of the categories.
Nature of compliance costs to charities and voluntary organisations
There are no anticipated costs for charities and voluntary organisations.
For each business sector, the extra control costs will be considered for each potential MEL value. However, some costs are common to all three potential MELs and although calculated for each sector separately, the basis for these costings is given below. The only common cost felt to be relevant is air monitoring. It is unlikely that companies would increase health surveillance as there are no validated health surveillance methods available. In addition, there is unlikely to be the need for additional training.
Monitoring
Monitoring of chlorobenzene would be required at sites where the risk assessment suggests that there may be a problem. It is likely that many companies will carry out an initial air sampling exercise as part of their reassessment of exposure compared to a new MEL. These costs are likely to be common to all, although most laboratories will simply reassess their control for the small amount they use and not carry out any air sampling. The number of companies then instigating routine monitoring programs is likely to be minimal as for most, and in particular laboratories, exposure will probably be significantly below the MEL. Most chemical plants only use chlorobenzene infrequently therefore there also are unlikely to instigate routine monitoring programs. In addition, some of the chemical plants using chlorobenzene already undertake air monitoring.
For the monitoring of chlorobenzene we can calculate some typical costs. A day's time for a consultant is estimated to cost between £500 and £600. A day's time for a technician is estimated to cost between £200 and £300 and the cost of each chlorobenzene analysis is assumed to be £20. A small business would require one day of a consultant's time with an average of 10 samples making a total of between £700 and £800. A medium sized business would require a consultant and a technician for one day plus the analysis of about 20 samples. This would add up to between £1,100 and £1,300. A large business would require the services of a consultant and a technician for 2 days and the analysis of about 40 samples making a total cost of between £2,200 and £2,600. It is extremely unlikely that a small business, in this case a laboratory, would carry out any air sampling. As stated above they would simply carry on using it in the fume cupboard. Since it can not be assumed that no laboratories will carry this out, it is estimated that 10 small businesses (laboratories) may carry out this initial air sampling, with a total initial cost of £7,000 to £8,000. It is also estimated that 10 medium sized businesses would carry out this air sampling with a total initial cost of £11,000 to £13,000, and 5 large businesses with a total initial cost of £11,000 to £13,000. Total one-off costs are therefore equal to £29,000-34,000.
It is further estimated that 5 companies would carry out this air sampling on a routine basis, with an annual total cost of £5,500 to £13,000 (independently on the level at which the MEL is set), assuming they are medium to large scale businesses.
Over ten years, in present value terms, total costs due to monitoring are therefore equal to about £75,200 -143,100, for any of the three levels of MEL.
(a) Repackaging and distribution.
(i) For a MEL of 1 ppm, 5 ppm or 10 ppm.
Five questionnaires were received from companies who either distribute or repackage chlorobenzene. One reported that they no longer supplied chlorobenzene. A further laboratory chemical supplier reported that they do repackage chlorobenzene and supply to laboratories, but that only one person day per year was spent on this work. The work is also carried out inside an extracted packaging station. The company reported that exposures were below the OES of 50 ppm 8 hour TWA, but did not report to what extent and did not report any anticipated compliance costs for a new MEL. A further supplier of laboratory chemicals reported they only supplied small quantities annually and therefore that worker contact with chlorobenzene was minimal.
One company did report costs for the investment of better facilities. The reported costs were £20K to £30K irrespective of the value of the MEL. This is a one off cost for the upgrade of the LEV system. Since this only an upgrade of the system, then additional (i.e. in excess of current maintenance costs) annual maintenance costs are likely to be minimal. They reported that only one employee out of a workforce of 17 was exposed to chlorobenzene and that LEV was used as the primary control measure. In 1999 packing operations were carried out seven times, each lasting no more than 8 hours.
The total number of companies in this sector is estimated to be between 10 and 15. If we assume that the companies who replied to the questionnaire are a representative sample of the sector, we then have that one fifth (i.e. between two and three companies) would face one-off costs to upgrade the LEV system, each of them at a cost of £20K-30K. One-off costs will, therefore, total between £40,000 and £90,000.
(b) Chemical plants
(i) For a MEL of 1 ppm, 5 ppm or 10 ppm.
Completed questionnaires were received from six of the 10 chemical plants targeted. Two of these stated that they no longer use chlorobenzene. Three of the remaining four respondents reported that exposures on their plants were less than 1 ppm 8 hour TWA and therefore they would have no further control costs. The remaining company reported that they used chlorobenzene only about 3 times a year for campaigns that only lasted a few days each. They were unable to report the current level of exposure on their plant and therefore could not estimate control costs at the three proposed values. They did suggest that they could control to less than 10 ppm for the duration of an activity. With their current process exposure only occurs for periods of up to 30 minutes, therefore 8 hr TWA exposure may be much lower depending on the number of occasions such activities take place in a shift.
Activities involving exposure to chlorobenzene on chemical plants tend to be short duration, in some cases only minutes, for example taking a process sample.
(c) Laboratory chemical use
(i) For a MEL of 1 ppm, 5 ppm or 10 ppm.
Compliance costs have not been received from companies using it as a laboratory reagent. In most cases the use will be infrequent, for example, as a high performance liquid chromatography (HPLC) solvent or for laboratory synthesis in research. Laboratory technicians are only likely to be using small amounts of chlorobenzene on an infrequent basis, for short duration activities, for example, preparing a reference standard. They also tend to use it in fume cupboards as for many hazardous chemicals, therefore the introduction of the MEL is unlikely to result in an impact at any of the levels proposed. This was confirmed through discussion with several laboratories.
Laboratories are also unlikely to carry out additional air sampling, health surveillance or training as a result of the MEL. They use many chemicals in small volumes and take generic approaches to control, in terms of what should be carried out in a fume cupboard etc. In general most chemicals are used infrequently such as not to warrant air sampling or health surveillance. In addition, any training is likely to be general to work in a laboratory and not specific to any chemical. It is therefore likely that costs to laboratories for the introduction of the MEL would be small.
(d) Adhesives
(i) For a MEL of 1 ppm, 5 ppm or 10 ppm.
See paragraph 16.
(e) Short term exposure limit - all sectors
The results of the initial consultation with the sectors involved indicated that compliance costs for a MEL of 1 ppm 8-hour TWA would be negligible (see paragraphs 25 to 34). A second consultation exercise was carried out giving companies the opportunity to further comment on this outcome; that 1 ppm 8-hour TWA was achievable. It also gave companies the opportunity to comment on a short term exposure limit of 3 ppm 15-min TWA. Only one company contacted HSE after this second consultation exercise, stating that they would have no additional costs for these proposals. It therefore can be concluded that a short term exposure limit of 3 ppm 15-min TWA would not impose any compliance costs.
The information provided by the various sectors is quite limited. The quantifiable total costs to industry equal £115,200-£233,100 over 10 years, in present value terms, and do not appear to change with the level at which the MEL is set. The total costs for all the affected business sectors are summarised in Table 2.
Table 2: Summary of costs to comply with a variety of MELs,
present values over ten years (£).
| Business sector | Cost for a MEL of 1 ppm (£) | Cost for a MEL of 5 ppm (£) | Cost for a MEL of 10 ppm (£) |
|---|---|---|---|
| Costs common to all sectors (monitoring) | 75,200 - 143,100 | 75,200 - 143,100 | 75,200 - 143,100 |
| Repackaging and distribution | 40,000-90,000 | 40,000-90,000 | 40,000-90,000 |
| Chemicals | no other quantifiable costs | no other quantifiable costs | no other quantifiable costs |
| Laboratories | no other quantifiable costs - likely to be small | no other quantifiable costs -likely to be small | no other quantifiable costs - likely to be small |
| Adhesives | no information provided by industry | no information provided by industry | no information provided by industry |
| Total present value (ten years, £) | 115,200 -233,100 | 115,200 -233,100 | 115,200 -233,100 |
As part of a regulatory impact assessment small-sized businesses are normally contacted to determine the impact for this sector. This was difficult for chlorobenzene as none of the uses are specifically for small sized businesses. Its use as a chemical intermediate tends to be with large companies. Similarly for repackaging and distribution. Most laboratories using chlorobenzene are either universities or on large chemical plants. It is possible, however, that some laboratories are small firms. A number of universities were contacted as the users tended to be individual departments and they are more akin to a small business. Those contacted confirmed earlier investigations that they only used small amounts infrequently and that they handled chlorobenzene in a fume cupboard. They did feel that a MEL at any of the proposed values would not pose any additional cost. They would not carry out additional air sampling, training etc. for the reasons given in paragraph 33. The only action reported by one university laboratory was that they would send an instruction that chlorobenzene should always be handled in a fume cupboard. Even though small universities laboratories are not small businesses, it is likely that their activities and uses of chlorobenzene are similar to those in small businesses. This means that small businesses will therefore face minimal additional costs. In any case, it is likely that the impact will be proportional to the size, i.e. small businesses will not face disproportionate costs due to the introduction of a MEL, at any level.
Costs to HSE
Because of the proposed change to a MEL, there will be an increased emphasis on chlorobenzene exposure at all premises during inspection visits. However, since there are only a few companies handling chlorobenzene any increased workload for inspectors, and therefore any additional costs, are likely to be minimal.
Total costs to society
The vast majority of the societal cost is borne by industry. This is detailed above.
There are no environmental impacts other than the health effects already discussed. The external environmental effects of diffusing chlorobenzene using local exhaust ventilation are negligible.
Since benefits are unquantifiable, it is not possible to compare total costs and total benefits. We know, though, that there might be between 700 and 1500 workers exposed to chlorobenzene, and that total quantifiable costs add up to £115,200-233,100 over a period of ten years, in present value terms.
It is useful to consider what the costs per worker exposed are from setting a MEL for chlorobenzene, and how these costs compare with past MELs. Given the total compliance costs and the number of workers exposed, the cost per employee exposed with setting a MEL at any of the three level is equal to £77-333. This is at the low end of the range of costs per employee exposed obtained for MELs set for other substances.
Both total quantifiable costs and the cost per worker exposed appear to be fairly low.
On the basis of the information obtained from industry, costs do not seem to vary with the level of the MEL, and they are also likely to be quite low. We have no information on the adhesives sector and we therefore cannot comment on the impact on this sector. As far as the other sectors are concerned, the only quantifiable costs are those relative to monitoring, and LEV costs that some of the firms in repackaging and distribution may face.
In general, the responses to our questionnaire seem to suggest that exposure is currently mostly below 1 ppm and that, therefore, costs to industry are likely to be small. This also implies that workers are already benefiting from a high degree of control, and, therefore, the benefits from introducing a MEL, at any level, are not likely to be large.
In view of the information collected to date, we recommend to set the lower levels for a MEL (1 ppm) and a STEL of 3 ppm.
Uncertainties
The information received from industry is rather scarce, thus many of the assumptions are based on limited replies to our questionnaire and HSE's best judgement. The uncertainties of the assumptions made is reflected in the use of ranges.
RESULTS OF CONSULTATION
The draft regulatory impact assessment was sent to all those companies identified as either supplying or using chlorobenzene. The cover letter stated that current investigations showed that there would be no impact at 1 ppm 8-hour TWA. Only one company responded by the deadline given, stating that they would have no problem with complying with a MEL at this value.
Arrangements for monitoring and evaluation
The proposed MEL will be enforced by HSE at the premises where they are the enforcing agency and by the Local Authority at premises where they are the enforcing authority. Because of the proposed change to a MEL, there will be an increase in the emphasis inspectors attach to chlorobenzene exposure. However, since there are only a few companies handling chlorobenzene any increased workload for inspectors is likely to be minimal. The MEL will be revised if significant new information becomes available which places doubt on the current assessment of the health risks.
1. In arriving at ten year cost figures, two adjustments are made. Firstly, earnings are assumed to rise by 1.8% per year in real terms - the observed increase for the whole economy over the past twenty-five years or so. Secondly, costs are discounted to present value using the Treasury recommended 6% discount rate.