A change in the rules governing how companies make provisions against pollution could create a boom in demand for specialised environmental cover.
The integrated pollution prevention and control rules require many industrial sectors to offer financial protection against pollution.
The rules already apply to the waste industry and are being phased in to other sectors over the next five years.
Environmental insurance specialist Graham de Roy of Lloyd's broker Tyser said insurers had shied away from the sector for years, but the market was now set for huge growth.
He said: "At least 50,000 companies will have to make financial provision, which could be catered for by a properly tailored insurance policy."
Industries affected include printing, textiles and food.
Pressure to build on brownfield land is also creating a rise in the number of companies vying to clean up old industrial sites or landfill areas for development. They need cover against contamination of such sites.
Tyser represents the insurance industry on the contaminated land working group of the government's urban taskforce, chaired by architect Lord Rogers.
The broker, the oldest at Lloyd's, leads the field with a policy written for contractors cleaning the site rather than the end user.
Average premiums are about £20,000 in the sector and policies usually offer limits of about £5m.
