Columbia subject headings:
Air--Pollution--Congresses.
Radioactive pollution--Congresses.
Water--Pollution--Congresses.
Harvard subject headings:
Air--Pollution--Congresses
Radioactive pollution--Congresses
Water--Pollution--Congresses
Princeton subject headings:
Air--Pollution--Congresses.
Radioactive pollution--Congresses.
Water--Pollution--Congresses.