Volume 6: Human Health, 1989-96
8. Development of guidance on occupational risks from BSE and other TSEs
Guidance produced by ACDP
Structure and function of ACDP
Guidance produced by ACDP Working Group
Fast-track letter to neurosurgery staff
The Guidance Document 'Precautions for work with human and animal Transmissible Spongiform Encephalopathies'
Further developments
EC Directive on the classification of biological agents

Structure and function of ACDP

8.153 As described in Annex 2, HSC/HSE operates with the assistance of advisory Committees. One of these, the ACDP (Advisory Committee on Dangerous Pathogens) had a significant role in the preparation of guidance in relation to BSE.

8.154 The ACDP was set up by HSC and DH in 1981. It had a tripartite membership, consisting of an independent chairman (Dr David Tyrrell from 1981 to 1990; Dr Michael Crumpton from 1991 to date), with representatives of employers, employees and specialist members selected from nominations by professional bodies. It had a dual (HSE/DH) secretariat. HSC's Annual Report of 1986/87 described ACDP's role as follows:

The Advisory Committee on Dangerous Pathogens (ACDP) advises Health and Agriculture Ministers as well as the Commission [HSC]. ACDP advises on general standards of safe working in laboratories handling dangerous pathogens; new hazards involving pathogens; control measures; categorisation of pathogens according to hazard; and research on pathogens. ¹

8.155 The ACDP's terms of reference were widened in October 1991, and its membership made more compact. A briefing note prepared for the first meeting following these changes said:

Membership

The newly reconstituted ACDP now consists of 8 'expert members' (whose names are selected from suggestions solicited from a range of professional associations), 4 representatives of employers and 4 of employees. (In the past there were 10 plus 6 plus 6 members respectively.) This arrangement upholds the standard tripartite structure of all HSC advisory Committees.

Terms of reference

The new terms of reference of the ACDP (see below) were very much supported by the Commission and the Health Minister. They represent a sharp change away from the largely laboratory safety angle of the old terms of reference which were prompted by the Birmingham smallpox outbreak in 1978. There was however enough latitude in the latter to allow some other issues to be put before the Committee but the change is designed to encourage as wide a selection of business as possible. HSE can now more comfortably address the needs of other occupational groups through the ACDP.

The new terms of reference are:

To advise the Health and Safety Commission, the Health and Safety Executive and the Health and Agriculture Ministers, as required, on all aspects of hazards and risks to workers and others from exposure to pathogens. ²

8.156 As explained earlier (see paragraphs 8.24-8.26), one of ACDP's functions was to review and categorise pathogens into four Hazard Groups and publish the findings. ³

ACDP's precautionary note on the BSE agent: 1990

8.157 The ACDP categorised CJD, GSS and kuru as Hazard Group 2: agents that might cause human disease and might be a hazard to laboratory workers but were unlikely to spread to the community. ⁴ The second edition of the ACDP's guidance note 'Categorisation of Pathogens according to Hazard and Categories of Containment' (published in 1990) contained an appendix entitled 'Slow Virus Infections of the Central Nervous System'. ⁵ The appendix dealt only briefly with BSE, and although the agent was not allocated to an ACDP hazard group, the application of Containment Level 2 precautions was advised for laboratory work with the agent. It stated:

Following detailed examination of BSE by the Southwood Committee it is clear that at this stage there is insufficient evidence on which to consider the allocation of the agent responsible for this newly emerged encephalopathy to an ACDP hazard group. However, while uncertainty remains about the potential for its transmission to man, it is prudent to treat known or suspected BSE-affected tissues with caution when working with them in the laboratory or animal room. Containment level 2 precautions with additional measures to guard against puncture wounds and cuts and the contamination of broken skin and eyes are considered to be appropriate. There is no specific information at present on the susceptibility of the BSE agent to heat and chemical disinfectants. ⁶

Establishment of the ACDP Working Group on SEs

8.158 In September 1990, the ACDP Secretariat circulated a paper on slow viruses to the members. It referred to the 'recent emergence' of BSE, and stated that this had 're-stimulated interest in the wider field of slow virus infections in general'. It reminded members of the new appendix on slow virus infections added to the second edition of the ACDP guidance note mentioned above. It continued:

The Secretariat is not aware of any conclusive evidence to show that the agent of CJD has been responsible for occupational infections although there are anecdotal reports of cases in workers exposed to neurological tissue. There are documented instances of patients known to have been infected by means of contaminated surgical instruments, certain human tissue implants and transplants and the use, in the past, of human growth hormone prepared from cadaver pituitary glands.

As all members will know, there is as yet no other evidence to suggest that the agent responsible for BSE presents a risk to man either from food or occupation.

Although on present evidence the agent of CJD does not appear to represent a significant occupational hazard it is suggested that in the current climate of concern it may be appropriate for the ACDP to draw together all the relevant information on the subject. (Science, the potential risks, the means by which the agent(s) concerned may or may not be inactivated, the properties of slow viruses and some detail on appropriate control measures). A distinct publication carrying the ACDP's authority could be useful in a number of working environments. These would include, for example, neurosurgery, neurophysiology research, histopathology Departments, post-mortem rooms, anatomy department dissection rooms and embalmers' premises. Those working on slow viruses in laboratories and animal rooms may need additional guidance in dealing with everyday practical problems such as decontamination of safety cabinets, disposal of filters, treatment of reusable glassware and instruments etc. New scientific evidence supports the current advice from the Department of Health although DA(81)22 and DA(84) 16 may need some modification.

If the Advisory Committee considers that guidance of this type is appropriate at this time, it will be important not to raise alarm by implying that the risk of slow virus infection has increased. There is no evidence to support this.

At present, the problem is that the facts and guidance that are available are scattered and there may be a case for drawing it together for the information of those with concerns in this field.

Therefore, the Committee is asked to consider the following:

Is there a need for a compendium of up-to-date information and/or guidance on slow viruses?

If so, to whom should it be addressed?

Is the ACDP the most appropriate body to produce a document of this nature?

Members will recall being issued with a copy of the Southwood Report at an earlier meeting. This contains some useful background information on slow viruses. ⁷

8.159 After further discussions on this matter at subsequent meetings, and consultation with DH, the minutes of the ACDP meeting on 4 December 1990 record:

Dr Harper [DH Secretariat] informed members that, following consultation with the Department of Health, the suggestion that a document carrying ACDP's authority would be a most useful and effective means of providing the necessary guidance, was readily accepted.

The Chairman agreed that ACDP should accept the request for guidance in principle. He pointed out, however, that ACDP's work in producing guidance on health surveillance and risk assessment had to take priority. It was agreed to set up a small Working Group, with co-option of outside members with specialist knowledge as necessary. ⁸

8.160 Accordingly, in February 1991 the ACDP Working Group was established. It met eight times between March 1991 and May 1993. Its terms of reference were:

To report to the ACDP on the need for additional guidance on health and safety aspects of work with animals or humans, their tissues or in vitro systems infected or potentially infected with spongiform encephalopathy agents, and to draw up such guidance. ⁹

8.161 The ACDP Working Group was chaired by Professor Biggs (although the first two meetings were chaired by Dr Pickles). It consisted of four ACDP members: Professor Biggs, Mr Clare, Mr P Taylor and Dr Wyatt. Other members were:

1. Dr D Taylor and Dr J Bell (Neuropathogenesis Unit);
2. Dr Jeffries and Mr A Taylor (HSE Advisory Committee on Genetic Modification);
3. Ms Heywood, Specialist Inspector Biohazards (Dangerous Pathogens) from HSE.
4. Dr Pickles, Ms McGinty, Mr Sweasey, Mr Lister.

8.162 The guidance drafted by the ACDP Working Group was agreed by the main Committee in June 1993, approved by the HSC and Health Ministers, and finally published in July 1994. It focused primarily on CJD and other known TSEs and only incidentally offered guidance on potential BSE risks. ¹⁰

8.163 The ACDP Working Group was wound up in 1993 ¹¹ and any subsequent TSE issues were dealt with by the main ACDP Committee (until the announcement on 20 March 1996).

Guidance produced by ACDP Working Group

Dr Pickles produces a background working paper: the Reference Document

8.164 Before the ACDP Working Group had their first meeting Dr Pickles prepared a draft guidance note entitled 'Spongiform Encephalopathy and Exposure at Work'. ¹² She told us that she had given considerable attention to the need for updated guidance to certain occupational groups.

The pressing practical issues were first, for the neuropathologists who were conducting examinations as part of the CJD surveillance project and secondly, for the many laboratory scientists who, thanks to new funding, were moving into this area with a biological agent which did not seem to obey the rules, especially in relation to susceptibility to disinfection procedures. ¹³

8.165 The paper itself was divided into several sections, including a review of the current guidance, ¹⁴ a discussion of the pathogenicity of SE agents and their decontamination, and recommendations for possible areas for guidance and research. The paper noted that CJD, GSS and kuru were known TSE agents in man and had been classified as Hazard Group 2 by ACDP. ¹⁵ BSE was, however, categorised as Hazard Group 1. ¹⁶ The paper explained that animal TSEs could be formally categorised only as 1 (non-pathogenic) as there was no evidence that any animal SEs had ever been transmitted to humans or that scrapie was causally linked to CJD.

8.166 The draft paper was sent to Mr Lister and Mr Sweasey. In her covering letter Dr Pickles set out her view that the main areas of work appeared to be human neuropathology in CJD and laboratory investigation particularly on the genetic modification side. She added:

I suspect none of us would have difficulties with authoritative advice in these areas. Inevitably, however, there will be anomalies with practices outside these settings, say for surgeons and others exposed to tissues of patients or veterinarians or farmers exposed to tissues of animals potentially but not known to be infected. To my mind it would be better to fudge these issues than abort the whole idea of getting advice out on the more clear-cut priority areas. ¹⁷

8.167 On possible areas for guidance, the paper set out the following for consideration:

Human SEs:

- clinical management in CJD (and for informal carers)

- general pathology/surgery/tissue handling in CJD

- neuropathology in CJD/GSS

- more general aspects of neuropathology or handling of tissue with a high risk of infection in subclinical cases.

Animal SEs:

- human agents or PrP genes in experimental animals

- neuropathology or in vitro studies in animal SEs

- handling of animals with clinical SE or their tissues (a) laboratory (b) veterinary/surgical procedures (c) farm or field

- handling of 'high risk' tissues from potentially asymptomatic cases eg on farm. ¹⁸

The Reference Document and the Guidance Document

8.168 Dr Pickles's draft paper was discussed at ACDP Working Group's first meeting, on 28 March 1991. ¹⁹ The Group decided:

. . . that in view of recent developments a new guidance document on SE was needed for workers exposed or potentially exposed to all the SE agents. ACDP was thought to be the most appropriate body to bring this guidance together with expert input on specialist areas such as neuropathology, GM experimentation and disinfection procedures as required. ²⁰

8.169 At the second meeting, on 13 May 1991, the paper was adopted as a working document for internal use. ²¹ After the meeting Dr Pickles wrote to Mr Lowson (MAFF) and noted, among other things, that the draft paper 'was considered of an inappropriate weight to be accessible to an audience that covered farm workers as well as laboratory scientists'. ²² It was to be used as the basis for a briefer practical guidance for wider circulation in the work-place.

8.170 From this point Dr Pickles's draft paper was called the 'Reference Document'. The briefer practical guidance was called the 'Guidance Document'. Both were to undergo protracted revisions.

Fast-track letter to neurosurgery staff

8.171 When ACDP Working Group began consideration of both the Reference Document and the Guidance Document it became apparent that the drafting process was to be a lengthy one and that neurosurgical staff, who were considered at particular risk, needed more urgent advice.

8.172 It was decided that such advice would be fast-tracked through a 'Dear Doctor' letter. In October 1991 the ACDP Working Group Secretariat circulated a draft letter on precautions to avoid cross-contamination with TSE agents in neurosurgery. ²³ The covering note from the Secretariat presented the draft letter as 'possible fast-tracking of guidance for neurosurgery staff' and commented that the 'guidance on SEs that is currently being developed will deal with this but inevitably it will be some months before it is published'. ²⁴ The fast-track letter (also referred to as the Professional Letter (PL)) was the first guidance produced by the ACDP Working Group. However, it took 14 months to agree.

8.173 During that time the ACDP Working Group worked on the draft in consultation with DH. The letter ultimately went through five drafts ²⁵ and a number of rounds of consultation within both DH and HSE and with the advisers to the CMO ²⁶ and SEAC. ²⁷ It was eventually issued to relevant medical professionals through the office of the CMO on 8 December 1992, entitled 'Neuro and Opthalmic surgery procedures on patients with or suspected to have, or at risk of developing CJD or GSS'. ²⁸ It covered the handling of surgical procedures involving patients with CJD-type diseases and dura mater recipients. It did not cover guidance for situations involving corneal implants. ²⁹

8.174 Professor Biggs told us about the fast-tracking of guidance for neurosurgery work:

This was considered by the WG to be urgent and of importance such that it at times took priority over the Reference and Guidance Documents in the time of the Secretariat. It apparently had an unexpectedly difficult consultation period within the DoH partly due, I was informed, to the sensitivities of possible litigation by recipients of human growth hormone and partly from initial disagreements of some over the inclusion of recipients of duramater in the high risk category . . . ³⁰

Decision to put the Reference Document aside and develop the Guidance Document

8.175 The Reference Document also went through extensive redrafting and consultation. However, in January 1992, after the fifth meeting of the ACDP Working Group, it was decided that the Guidance Document should take precedence over the Reference Document. ³¹ In the event the Reference Document was never issued. At its seventh meeting in May 1993 the Working Group considered that extensive re-drafting and up-dating would be required to compile the proposed Reference Document 'which would only be of value if it was kept regularly up to date in any case'. ³² It was agreed that:

ACDP should aim to issue the guidance document only, although the benefits to workers and others, if a 'reference' document were to be produced in another quarter were fully appreciated by members. ³³

The Guidance Document 'Precautions for work with human and animal Transmissible Spongiform Encephalopathies'

ACDP Working Group deliberations

8.176 By the time the ACDP Working Group decided to stop work on the Reference Document, the Guidance Document had already undergone four drafts. ³⁴ It then underwent three more drafts and rounds of consultation before publication. ³⁵

8.177 On 28 March 1994, Dr Roger Skinner (Principal Medical Officer, DH) submitted the final draft of the guidance to Dr Metters (Deputy CMO) seeking endorsement from the Ministers. ³⁶ In his covering minute Dr Skinner said:

The emergence of BSE in the late 1980s re-stimulated academic and scientific interest in human and animal TSEs. At the same time, awareness of potentially contaminated tissues and body fluids from animals or humans who had or were suspected of suffering from a TSE was heightened.

. . .

In view of the increasing activity in this field and the lack of existing guidance for work with TSEs, the ACDP at the request of DH undertook to produce comprehensive guidance covering work with these agents. ³⁷

8.178 On 15 April 1994 Mr Sackville (Parliamentary Under-Secretary of State, DH, 1992-95) approved the issuing of the guidance. ³⁸ After some delay the Guidance Document was eventually published in September 1994. ³⁹

Content of 1994 ACDP guidance: 'Precautions for work with human and animal Transmissible Spongiform Encephalopathies'

8.179 The published guidance, divided into four parts, aimed to draw together the basic facts about TSEs in order to provide information for all concerned in laboratory work, in clinical care and animal handling. The guidance gave particular advice to laboratory workers, health care workers, pathologists, anatomy and pathology teachers, post-mortem workers, embalmers and veterinarians and was divided into the following general sections: ⁴⁰

1. Part I 'Introduction' included sections on the TSEs, diagnosis of TSE infections, the nature of TSE agents and transmission of TSEs;
2. Part II 'Hazards and risks' comprised sections on hazard categorisation of TSE agents and hazard containment;
3. Part III 'Control of infection and containment' included sections on Control of Substances Hazardous to Health (COSHH) Regulation requirements, basic precautions to avoid exposure, accident reporting and health surveillance, as well as sections on exposure to human TSE agents in the health care setting ⁴¹ and exposure to animals with TSE ⁴²;
4. Part IV 'Decontamination and waste disposal procedures for TSE agents', highlighting ineffective and effective methods of decontamination.

Further developments

8.180 In 1995 ACDP published the fourth edition of Categorisation of biological agents according to hazard and categories of containment. ⁴³ Appendix 19, entitled 'Transmissible Spongiform Encephalopathies', listed BSE as a known TSE. It stated:

Following detailed consideration by the Southwood Committee and other groups since then, it is clear that there is insufficient evidence on which to consider the allocation of the agent responsible for BSE to an ACDP hazard group. However, whilst uncertainty remains about the potential for its transmission to humans, it is prudent to treat known or suspected BSE-affected tissue with caution. The new guidance addresses this issue and also provides recommendations applicable to work with other animal TSE.

8.181 On 18 April 1996, ACDP and HSE issued a press release entitled 'Review of BSE guidance issued to occupational groups'. This stated:

Following a recommendation made by the Spongiform Encephalopathy Advisory Committee (SEAC), which was announced by the Secretary of State for Health in a statement to the House of Commons on March 20 1996, the Advisory Committee on Dangerous Pathogens (ACDP) has met to review all the guidance on bovine spongiform encephalopathy (BSE) issued to workers in various occupational groups.

. . .

The ACDP has re-examined, in light of current evidence, the principles of the control measures recommended in the various guidance publications for abattoir workers, farmers, laboratory workers, vets, zoo-keepers and others published since 1990.

The ACDP advises that, subject to some adaptation to specific occupational settings, the prudent precautions incorporated in the current guidance remain valid.

The Committee considers that there is no evidence of risk of transmission of BSE to humans from contact with live cattle in normal farming practices, or in dealing with their carcasses. Furthermore in considering likely routes of transmission, it is the Committee's opinion that transmissible spongiform encephalopathies (TSEs), including BSE, are unlikely to be transmitted by the respiratory route. Nevertheless, the Committee strongly recommends that high standards of personal and occupational hygiene are maintained. Most importantly, there is a continuing need to protect persons in exposed occupations against splashing by specified bovine material (SBMs) especially those from the central nervous system. ⁴⁴

8.182 In June 1996, the ACDP issued BSE - (Bovine spongiform encephalopathy) Background and general occupational guidance. The guidance stated:

This new more general guidance, which has been agreed by the Health and Safety Commission and Health and Agriculture Ministers, is based on the most up-to-date knowledge and if it is followed then it is considered that workers will have a negligible risk of being exposed to BSE. Its main purpose is to provide information about BSE and to re-emphasise the need to use the precautionary protective measures that are judged to be generally appropriate.

People responsible for health and safety matters in the various workplaces where there is contact with material that may be contaminated with the BSE agent, especially those newly involved in disposal operations, will find this guidance helpful in developing local codes of practice for the safe conduct of the work. In addition, the separate sector-specific publications, which provide more detailed information, are being revised to reflect the principles incorporated in this document. ⁴⁵

8.183 The guidance listed those who might be exposed to BSE. This included farmers, veterinary surgeons, hauliers, slaughterhouse workers, renderers, incinerator operators, maintenance engineers (eg, in abattoirs, rendering plants, incinerators) and land-fill site workers where rendered material is disposed of. Other groups of workers included those involved in the storage of greaves or meat and bone meal. The guidance gave general background information about BSE and went on to reiterate the advice given in the press release of 18 April.

EC Directive on the classification of biological agents

8.184 During the early period of the work of the ACDP Working Group, the EC ⁴⁶ was negotiating a directive on the classification of biological agents. Mr Lister told us:

Meetings on 'biological agents' convened by the European Commission...began in the late 1980s. These concerned the development of a Directive to do with protection against exposure to biological agents (ie bacteria, viruses, fungi and parasites) at work including those causing spongiform encephalopathies which were known at that time to be transmissible to humans. HSE was fully involved in these formative meetings.

When the proposed Directive on control measures (90/679/EEC) ⁴⁷ was finally put forward for adoption, the HSE, as the body concerned with health and safety legislation in the UK, worked in very close collaboration with UKREP (United Kingdom Permanent Representative in Brussels) in negotiating the terms of the Directive at meetings of the Social Questions Working Group of the Council of Ministers of the EU. I attended about a dozen of those meetings in Brussels along with an administrative colleague from HSE. I do not recall any mention of BSE at that time.

However, a later Directive, amending the first, concerned a classification of biological agents (ranked in risk/hazard groups 1 to 4) ⁴⁸ Preparatory work on this was the function of a group of 'national experts' convened again by the EC at which all Member States were represented. I represented the UK (via HSE) with support from my fellow joint secretary of the ACDP and on several occasions also a member of HSE's THSD. The line to take at all these meetings was, where time allowed, prepared in consultation with ACDP and others and, where necessary, with Ministerial approval. ⁴⁹

8.185 On 30 May 1991, Ms McGinty reported to Dr Pickles about a recent EC meeting to discuss the draft directive. She said:

As anticipated there was considerable pressure from the other member states at the last meeting of experts in Luxembourg to classify the agents of CJD, GSS and Kuru in Group 3 rather than Group 2 (our current classification). There seemed to general agreement that the agents of BSE and scrapie should be excluded from the list on the basis that they are animal infections with no evidence of human pathogenesis, and there should be no difficulties in defending this position.

However, in order to resist pressure to up grade the human SE agents we will need some convincing arguments as to why lower classification is appropriate.

. . .

If you consider that we should resist the classification of human SE agents to Group 3, and that the political and practical consequences of not doing so are too great, I can put a reserve on this classification. We will hopefully get a further chance to discuss matters when the draft Directive is considered by the [EC] Social Questions Working Group, though it is unlikely that this group will be willing to overthrow the decision of the national experts without very good reason. ⁵⁰

8.186 The ACDP Working Group was kept informed about developments on the draft directive. In August 1991 Mr Lister reported to the Group that the EC Working Group on the directive had prepared a final draft on the classification, which included human SEs as Group 2 and did not list animal SEs. He advised that the draft proposal would be put to the Commission's Advisory Committee for Safety, Hygiene and Health in September. He expected that the directive might be adopted 'later in 1992'. ⁵¹

8.187 Professor Biggs told us that, at the sixth meeting of the ACDP Working Group on 15 June 1992, the members were informed that the draft directive was likely to classify the human TSEs in Hazard Group 3. He continued:

The UK did not agree with this and was negotiating for a derogation on containment for these agents to be handled as group 2+. Because it was likely that these negotiations would be prolonged, I agreed with the Secretariat in January 1993 that we should proceed to finalise the Guidance on the basis of the current ACDP categorisation of these agents as group 2. ⁵²

8.188 The Directive was adopted in 1993 (Directive 93/88/EEC) and classified the agents responsible for human TSEs in Hazard Group 3. The Directive also recommended the use of a Containment Level 2 for laboratory work with the BSE agent. ⁵³

8.189 Mr Lister told us:

In the absence of any evidence in 1995 and very early in 1996 of a compelling link between BSE and human disease (and there is still none in relation to occupational exposure), it was appropriate for the UK to resist the moves made by several of the Member States (notably Germany, Austria and initially France) to have BSE classified formally as a biological agent under the terms of the Directive. Such premature classification, and its consequent implementation in domestic legislation as would have been required, may have had a profound effect in terms of limitation of important research activities in the UK and in many other respects could have been damaging to the UK's interests. (Later on, in 1996 or 1997, when the link between BSE and nvCJD was more firmly established, the UK itself, via HSE's representation at further EC meetings, proposed the appropriate classification of the BSE agent. Notably though, a suitable derogation from the full stringency of containment measures was successfully negotiated as this had already been applied to CJD and other human spongiform encephalopathies. There is no proven record of CJD having been transmitted through occupational exposure and for some years containment measures have been modified accordingly). ⁵⁴