A proposed waste incinerator for a quarry near Ivybridge in Devon will create some emissions but will not harm people, the Environment Agency says.
The plans, by waste company Viridor, are for its New England Quarry. A new landfill site has also been proposed.
Critics have raised concerns about potential contamination to the area.
The agency, which has already said it was "minded to"' grant Viridor a permit, said any level of pollutants would be small.
Viridor originally came up with its plans when a tender was put out by the South West Devon Waste Partnership for an incinerator to deal with local waste disposal.
That contract was won by MVV Umwelt. An incinerator in Devonport, Plymouth, is currently under construction.
'Head in the sand'
However, Viridor said it was carrying on with its proposed plant to deal with "municipal solid waste and commercial waste" because it still considered the project to fit in with Devon County Council's Local Waste Plan.
If approved, the energy-from-waste plant will deal with about 275,000 tonnes a year.
At a public surgery in Ivybridge, Judy Proctor, from the Environment Agency, said the organisation understood why people were worried.
She said: "There will be emissions from the stack, and that is what we want to explain to people.
"But what we can show is that they will be at very small levels and they will not harm human health."
However, critics said they were still concerned.
Andy Rowell, chairman of the Devon Alliance for Incineration Alternatives opposition group, said the agency's analysis was "flawed" and the plant would still be polluting during its construction and operation.
He said: "Basically, they've stuck their head in the sand when it comes to air pollution and the risk to the River Yealm."
Planning permission is still needed from Devon County Council as well as the environmental permit from the agency for the incinerator.
A public consultation by the agency is to finish on 12 October. The county council is to debate the application on 24 October.