Acid rain or snow, with annual acidity value averaging about pH 4, is falling on most of the Northeastern U.S. This acidity of the precipitation apparently increased about 20 years ago (i.e., 1954) and may be associated with the augmented use of natural gas and with the installation of particle-removal devices in tall smokestacks. See also AATA 17-1045. Many adverse ecological and economic effects result from this acid rain. See also AATA 17-223. -- AATA