Unlike the booming decades of the '70s and '80s, the last decade of the 20th century was a bust for the environmental services industry.

From 1990 to 1998, U.S. industry revenues grew only 28 percent a far cry from the 138 percent growth in the 1970s and 147 percent growth in the '80s.

The slowdown is largely attributable to government cutbacks, increased competition and fewer regulations, as environmental issues slip ever lower on the government's priority list.

The top 25 companies on this year's list of environmental firms employ a combined 6,268 workers, 4 percent fewer than last year. Many of these firms are consulting and engineering companies that assist businesses in complying with environmental regulations and/or perform such services as pollution prevention, hazardous waste material removal, wastewater treatment, and asbestos and lead abatement. Seven of the L.A. County-based companies on the list are among the top 35 companies nationally, according to the Environmental Business Journal.

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