Alert issued on diacetyl vapour

A new HSE safety alert warns that exposure to diacetyl vapour, often used as a flavouring and a by-product of coffee roasting, can lead to severe and irreversible lung disease. Even exposure to low concentrations of the vapour within mixtures or flavourings may be above safe workplace exposure limits (WELs).

In the alert, the regulator outlines the risks in coffee manufacture, during roasting and grinding. Concentrations are significantly greater if the roasted beans are ground when still warm, around 40°C, and reduced if beans are cooled between roasting and grinding down to room temp, around 16-20°C.

In flavour manufacture, it says, airborne concentrations and the potential for exposures above safe workplace limits is significantly increased if flavour mixtures containing diacetyl, even at low concentrations of below 5%, are heated, added to hot processes, or spray dried. Diacetyl vapour may also be present during brewing of some beers.

The Control of Substances Hazardous to Health (COSHH) Regulations 2002 require employers to ensure work-related exposure is assessed, prevented or adequately controlled so that it is below the WELs, and sets out the action required. This includes carrying out risk assessments, checking safety data sheets, using sampling and analysis, and working through a hierarchy of prevention and controls, beginning with substitution with a safer alternative product.