The National Environmental Policy Act and the environmental statements it requires have been popular targets for lawsuits since the law was passed in 1969. Here are some statistics about NEPA litigation, as provided by the most recent annual report of the Council on Environmental Quality.

* In 1981, 114 suits were filed, based at least in part on NEPA. That compares with 140 suits in 1980 and a low of 108 in 1977.

* That same year, the Defense Department was sued the most (19 percent of the suits), followed by the Transportation Department (18 percent), Interior Department (15 percent), the Agriculture Department (13 percent) and the Housing and Urban Development Department (8 percent). The Nuclear Regulatory Agency was the independent regulatory agency that was sued most frequently, 6 percent of the total.

* Environmental groups were the most frequent plaintiffs, filing suit in 40 of the 114 cases. Individuals or citizen groups were involved in 32 cases; local governments, 24 cases; business groups, 16 cases; affected property owners and residents, 13 cases; state governments, nine cases; Indian tribes and labor unions, each two cases; and a legal foundation, one case.

* Since the law was enacted, the most frequent allegation in lawsuits based on it has been that an agency failed to prepare an environmental impact statement for a major action that would affect the environment. In 1981, 52 of the cases were based on that premise. The inadequacy of an impact statement or an environmental assessment was cited in 58 cases.