The waste incinerator that Indaver Ireland wants to build in Carranstown, Co Meath, would not be permitted in the United States, according to an American professor of chemistry, Dr Paul Connett.
He told the Environmental Protection Agency oral hearing into objections to granting a licence to the facility that the legacy of incineration was dioxin levels in food, body fat and babies.
He disputed statistics produced by a witness for Indaver Ireland who said the dioxin exposure for humans from the incinerator would be insignificant.
Instead, Dr Connett said, the exposure to dioxins could exceed the WHO's daily limit. The levels produced, he estimated, would translate into an incremental cancer risk of between 825 and 1,325 in a million.
"The US Environmental Protection Agency does not permit facilities with cancer-projected rates of over 100 in a million," he said.
Mr Garrett Simons, for Indaver, said its expert witness was standing over his findings in relation to dioxin levels and had used the American EPA's methodology.
It was also claimed that a condition included in the original EPA draft licence requiring Indaver to monitor specific dust emissions from the incinerator appeared to have been removed.
The claim was made by environmental consultant Jack O'Sullivan, representing Drogheda Borough Council, Dundalk Town Council and An Taisce.