Lead smelting at Avonmouth.

Abstract

A committee was appointed on 29 February 1972 under the chairmanship of Sir Brian Windeyer 'to enquire into the circumstances which gave rise to the cases of lead poisoning at the RTZ Smelter at Avonmouth and to report in the light of the con sideration at present being given by the Committee on Safety and Health under the chairmanship of Lord Robens to the general problems of health at work'. The committee reported to the Secretary of State for Employment on 23 June 1972. Lead and zinc smelting has been an established industry on the site at Avonmouth since 1917 and there is evidence of earlier operations there going back to the eighteenth century. The responsibility for the current smelter had rested with the Rio Tinto Zinc Corporation since 1962. A new plant was commissioned in 1968 which was an expanded version of a well-established process operated by the company in the United Kingdom and in 10 other countries under licence. The process consists fundamentally of oxidizing lead and zinc sulphide by combustion on a moving chain grate. The sulphur dioxide so formed is removed together with a mixture of finely divided oxides and eventually converted to sulphuric acid. The sintered oxides are fed into a blast furnace from whence the lead is tapped off at the base and the zinc is volatilized and sublimes in a condenser at the top of the furnace. There is no mention in the report of cadmium sulphide which is likely to be present as an impurity in the zinc sulphide and which would be converted to cadmium oxide during these operations. In particular, the first fraction of zinc given off during the blast furnace operation would probably contain most of the cadmium. The problems of cadmium poisoning and the release of cadmium salts were not included in the terms of reference of the committee and hence were not investigated by them. Between 1968 and 1972 there was a gradually increasing concern about the health of the workers on the site and about the possible pollution of the environment outside the site. The Factory Inspec torate had considered applying for a court order, the works doctor repeatedly drew the problem to the attention of the top management, and there was a loss of confidence in the management by the Trades Union. The company had tried to improve the performance of the plant while at the same time meeting the minimum standards of hygiene in the environment. The difficulties had been aggravated by frequent changes in local and higher management, a factor emphasized by the committee. Events were brought to a head by the death of a worker from an unrelated disease, and the diagnosis at a local hospital of lead poisoning in a worker certified as fit for employment by the company. Requests by the workers to examine the health register were refused and eventually a meeting of all parties, Factory Department, Medical Services, TUC Medical Adviser, works doctor, and company management, agreed to an early date for extensive modifications to be made to the plant by advancing the date for the annual overhaul programme. The hazard to the health of the worker in this process arises from inhalation of lead dust and to a lesser extent from ingestion. Evolution of dust is likely to happen during maintenance and cleaning operations and particularly during unplanned shut downs due to failure of the plant. The number of cases of lead poisoning notified to the Chief Inspector 199