The business concerned was owned by Perloplast until 1984, when it was acquired by its present owner, Du Vergier. The company recovers methyl methacrylate (MMA) from polymer scrap at a site in Hoddesdon.
The site has several reactors in which solid scrap is heated to drive off MMA as vapour, which is then condensed and redistilled. These operations, as well as MMA transfers, all have the potential to cause a severe odour nuisance without high standards of abatement, operation and housekeeping. MMA, like many acrylates, has a particularly pungent smell as well as a very low odour threshold of around 200ppb, so even a tiny spillage can be detected well away from the plant.
In 1984, when the business was still owned by Perloplast, the then Industrial Air Pollution Inspectorate (IAPI) reported an "intense" complaint situation, with "numerous" complaints about odours being received and the local MP pressing for a solution. Improvements were subsequently made by the new owner, but the odour problem continued:
HMIP was finally moved to take legal proceedings after an inspector visited the site in response to yet another complaint in September 1992. The case was heard by Cheshunt magistrates in July, but, unlike successful HMIP prosecutions, was not publicised at the time.
Du Vergier was charged under section 5 of the Health and Safety at Work Act 1974 with failing to employ the "best practicable means" to prevent emissions of "noxious or offensive substances" and to render "harmless and inoffensive" any residual emissions.
According to Du Vergier's "schedule" or permit, each depolymerisation reactor on the site must have its own MMA receiver fitted with a level control and alarm. HMIP's investigations revealed that after a receiver had corroded, the piping from the reactor concerned was transferred to another receiver which also served an adjacent reactor.
Magistrates were told by HMIP that the odour problem which attracted the complaint apparently resulted from the non-activation of the second receiver's level alarm, and that this in turn resulted from Du Vergier's failure to ensure that the control panels for both plants were switched on after the transfer was made. An MMA spillage apparently resulted, and indeed appeared to have been confirmed by a manager who had told the inspector that he had seen liquid in a bund beneath the receiver.
However, HMIP proved unable to stand up this version of events in court. It conceded that it had no direct evidence that both control panels had not been switched on at the time of the incident, but had inferred this from a management instruction issued after the inspector's visit. Du Vergier's manager told the court that although the liquid he had seen in the bund might have been MMA, it could equally well have been water. And a potentially crucial omission was that no statement by the plant operator at the time of the incident was brought in evidence by HMIP.
The Inspectorate was also left flat-footed after a key witness - a regular complainant - was called away at the last minute and was unable to appear in court. Eventually, magistrates concluded that there was no case to answer and threw out the charge.
Although the outcome was unsatisfactory for HMIP, it will shortly gain an additional weapon in its armoury. Processes such as Du Vergier's come under integrated pollution control next March, and under the new regime they will be under an explicit duty not to cause any offensive odour beyond the site boundary. Breaches of this requirement, though, will still have to be traced back to a particular event or source, and HMIP will have to sharpen up its approach to securing evidence if it is to succeed where it failed in the Du Vergier case.