The company behind the controversial Poolbeg Incinerator is facing a $80,000 fine in the US for dangerous workplace practices.
The hazards were uncovered at a waste-to-energy facility in Bristol, Pennsylvania, similar to the €500m unit under construction in Dublin.
The US Department of Labour's Occupational Safety and Health Administration (OSHA) inspected the plant in October after receiving an employee complaint. The watchdog cited the company for 16 serious violations of workplace safety and health standards.
The violations include toxic metals in ash, the dangers of falls or working in confined spaces, and electrical and mechanical hazards.
In its finding the OSHA said Covanta "needlessly exposed its employees to the hazards of electrocution, fire, falls, slips and trips, crushing, being trapped or overcome in a confined space, eye injuries and cancer, lung or kidney damage."
In July 2011, it also paid a $400,000 fine penalty after its Connecticut burn plant sent toxic dioxins into the air. It also paid a dioxin emissions fine in 2009.
The company said it intended to contest the OSHA's findings. "The health and safety of employees is our priority at Covanta so we take the recent citations at our Bristol facility very seriously," said a spokesman.
"We have reviewed the citations closely and have filed a notice to contest because we disagree with the assertions made by the OSHA."
The Dublin facilty will need to burn some 600,000 tonnes of waste a year to be profitable.
The company refused to confirm it would not be importing waste from other countries to burn at the site.