Residents living near the site in Southall, west London, have complained of poor health and breathing difficulties since work began in 2016.
Tonnes of earth have been cleaned during the work and the developers said they had met “regulatory requirements”.
Public Health England said there was “minimal” risk to health at the site.
Berkeley Group is regenerating the 88 acre (36 hectare) former industrial site at Southall Waterside to create thousands of homes, shops, a primary school and leisure facilities.
The Marsden family are among the residents who have said they noticed a terrible smell, described as a mix of chemicals and petrol, when earthworks first began and they had all suffered ill health since.
David Marsden, 52, said he had lost count of the number of chest infections he had suffered, while his five-year-old son Zion was hospitalised with viral-induced wheeze.
“He’s had to take a brown steroid inhaler morning and night basically just to keep his airways open. As parents it’s incredibly frightening to see your child like that and you feel powerless and helpless,” he said.