A two-year study has shown air quality near Castle Cement’s Padeswood factory is "good" according to the Environment Agency.
But the Agency said it was insisting on improvements after complaints about dust and noise from the works near Buckley.
Recently Coun Arnold Woolley, chairman of CANK (Campaign Against the New Kiln), highlighted huge increases in the amount of metals released into the atmosphere by the factory according to the EA’s own figures.
CounWoolley claims the increases are alarming and need investigating.
In a letter to residents, the Agency said: "It is our responsibility to ensure the site is operating within the limits set in its permit and does not have a harmful effect on the environment.
"We have completed a two-year air quality monitoring study in Penyffordd.
"The results show air quality in the Penyffordd area complies with these standards and is generally classed as good."