Two or three waste burning incinerators could be built within ten miles of one of Sussex's largest towns.
Campaigners from the pressure group No Incinerator in Crawley or its Environs (Nice) claimed they could be ringed by burners.
The claim came after Surrey County Council granted planning permission to build an incinerator at Capel, north-west of Crawley.
Meanwhile, West Sussex County Council is considering building at North Horsham and Wakehams Farm - both within a ten-mile radius of Crawley.
Spokesman for Nice Paul Smith said the Government should plan where incinerators were sited to avoid clusters of burners being built in the same area.
Mr Smith said fall out from an incinerator at Capel was likely to fall on Crawley and there would be more pollution if burners were built at one or both the other sites.
He said: "For people in Crawley, it does raise the possibility there could be three.
"Because the counties consider their own requirements in isolation, you could end up with two being built very close together, on either side of the county boundaries, which is a nonsense."
Surrey County Council's decision to back a burner at Capel has to be approved by the Environment Secretary, who may call a public inquiry.
The two West Sussex sites are among three being considered for waste-to-energy plants by the county council there.
It has yet to decide a final list of sites to be earmarked for incinerators and neither of the two near Crawley may eventually be selected.
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