A sharp rise in infertility blamed on China’s pollution is fuelling a booming surrogacy trade that allows wealthy Chinese to hire the wombs of working-class American women for $120,000 per baby.

Chinese inquiries to agencies that match couples from around the world with American surrogates have risen tenfold since 2012 and are expected to double again in the next two years, according to doctors and middlemen.

The unprecedented surge comes as infertility rates have risen to 12.5 per cent of all adults in China of child-bearing age, up from just 3 per cent 20 years ago. Sperm counts have dropped by 80 per cent in Chinese men in 40 years.

Surrogacy is illegal in China, so infertile couples have increasingly turned to the US for