It is estimated that 10,539 workers in the EU may be exposed to isoprene. At workplaces where isoprene is produced or used, exposure can occur primarily through inhalation of vapours and through skin contact, but dermal uptake is considered negligible. According to CLP, isoprene is classified as carcinogen category 1B (H350: May cause cancer). Chronic and high exposure may lead to liver cancer as the main effect, but also anaemia, degeneration of olfactory epithelium (the tissue inside the nasal cavity that is involved in odour perception) and degeneration of spinal cord white matter.

Where risks occur

Isoprene is used as a monomer in polymer production and -processing. Further, it is used as an intermediate in the synthesis of chemical substances. Exposure might also occur during manufacturing of isoprene or when it is used as sustainable aviation fuel. Workers in the sectors of manufacturing of industrial chemicals and plastic or rubber production are at risk of exposure.

More about the substance

Isoprene is a colourless flammable liquid with a mild odour. It has a low boiling point of only 34°C and thus an extremely high vapour pressure of 634 hPa already at 21.1 °C. This means it evaporates rapidly at room temperature. The released vapours can be inhaled or create an explosive atmosphere. Isoprene is a metabolite naturally occurring in many plants, animals and humans. Isoprene is emitted by many species of trees in large amounts (but degrades rapidly, meaning that environmental concentrations are low) and is also detectable in human breath. Isoprene itself is not genotoxic, but is readily metabolised to a genotoxic mono- and diepoxide, predominantly in the liver. Isoprene polymers are the main component of natural rubber. The most common products made from isoprene are tyres.

Hazards that may occur

The highest potential for occupational exposure to isoprene is through inhalation of vapours. A single or short-term exposure to isoprene can cause irritation of nose, throat and lungs, and can lead to headache or dizziness. Whilst acute toxicity is low (i.e., it is very unlikely to die from a single short-term exposure), long-term or repeated exposure to isoprene is associated with liver cancer, degeneration of the olfactory epithelium and degeneration of spinal cord white matter.

For liver cancer, the latency period is estimated to be 18 years.

What you can do

The most effective way to prevent exposure is substitution of isoprene by safer alternatives. Where substitution of isoprene is not possible and use of isoprene cannot be avoided, measures to reduce exposure must be taken. In the sector manufacturing of refined petroleum products, which is responsible for the production and not the use of isoprene, substitution is not applicable. However, using other monomers in the rubber industry might be an option. The second most effective way to avoid exposure to isoprene is to develop and use closed systems. Closed systems are commonly found across all the production processes in both the refining and the polymerisation of isoprene.

Where substitution or a closed process is not possible, technical measures such as effective local exhaust ventilation, or good ventilation of the workplace as well as checking their effectiveness should be implemented to ensure that exposure is minimised as much as technically possible. Isoprene is often processed in pressurised control cabs, which are very efficient in reducing evaporation.

Implement regular exposure assessments to check if your protective measures in place are effective or whether further actions need to be taken. Workers need to be aware of the effects of exposure and should be trained regularly on the control measures necessary for working safely with isoprene to prevent exposure. They should be encouraged to report symptoms such as irritation of nose, throat and lungs (e.g. coughing and wheezing), headache or dizziness, since they may be warning signs that measures in place are not sufficient. Involving an occupational physician is recommended.

In addition, train workers on effective hygiene measures.

Ensure that workers have adequate personal protective equipment (PPE), such as protective clothing and gloves, if necessary. If reusable PPE is used, take care that it is cleaned or replaced, if necessary, and stored at a clean place. For Isoprene, RPE (respiratory protective equipment) as well as protective gloves and goggles are often required. If respiratory equipment is necessary, ensure that breathing is not additionally physically demanding. Personal protective equipment should only be used as a last resort and only considered temporarily, after the possible technical solutions have been exhausted.

References: ECHA, RAC, DG EMPL