An Independent investigation has discovered that dozens, possibly hundreds, of Britons have been working without adequate protection and with little or no training.
Warner Brothers, which owns the pounds 200m Movie World park near Dusseldorf in north-west Germany, and ICI, which supplied some of the chemicals, are inquiring into the allegations.
The Independent has established that several workers have been injured. Others are worried that they may have suffered long-term damage after working next to toxic substances without protective clothing.
Despite assurances from the contractors and from Warner Brothers that the park, which describes itself as Germany's Hollywood, was tightly policed, and that all employees followed set regulations, an Independent journalist was able to walk unchallenged on to the site, where he witnessed dangerous practices.
Warner Brothers' 40-hectare Movie World opened a fortnight ago. It features funfair rides and other attractions based on blockbusters such as Batman, and Superman. Warner Brothers is planning to build a similar pounds 225m film and television complex in west London.
During the German project, artists worked at least 60 hours a week - some worked 90 hours - for pounds 7.50 an hour. Many have complained that they spent much of their time on repetitive manual work, rather than the creative work promised.
Mivan Ltd, an Irish sub-contractor with 4,000 employees, built much of the scenery. About 1,500 people, many of them labourers, were flown to Germany. Many left prematurely because of the conditions.
More than a dozen employees told the Independent that after little or no training they were expected to use electrical equipment such as chainsaws.
Many artists ground blocks of foam into scenery. A fireproof layer was then sprayed on and painted. Both layers contain the chemical diphenylmethane diisocyanate (DMI), which causes tumours in tests on animals.
The ICI hazard labels on barrels of DMI warn that it is "harmful by inhalation, may cause sensitisation by inhalation, irritating to eyes, respiratory system and skin".
Some artists said they had to make do with paper masks.
Peter Drillingcourt, Mivan's group health and safety manager, said that his supervisors were instructed to follow safety regulations, and that safety equipment was available, but conceded that: "Not everything was perfect."
Joe Meck, general manager of WB Movie World, added: "We are very concerned. We do not condone safety violations."