Columbia subject headings:
Environmental policy--United States--Statistics.
Nature--Effect of human beings on--United States--Statistics.
Pollution control industry--United States--Statistics.
Pollution--Law and legislation--United States--Statistics.
Pollution--United States--Statistics.
Sanitation--United States--Statistics.
Harvard subject headings:
Princeton subject headings:
Environmental policy--United States--Statistics.
Nature--Effect of human beings on--United States--Statistics.
Pollution control industry--United States--Statistics.
Pollution--Law and legislation--United States--Statistics.
Pollution--United States--Statistics.
Sanitation--United States--Statistics.