Indur Goklany sent the following e-mail to me in response to the last item in this recent “Some Links” post . I post Indur’s e-mail here, in full, with his kind permission.
Air pollution levels — both outdoors and more importantly, indoors (because that’s where most people spend their time) — had been improving for decades before the 1970s. See the figures in: IM Goklany, “The Environmental Transition to Air Quality .” Regulation 24 (4: 1998): 36-46.
With respect to water pollution, note that it has “traditionally been high on the list of environmental priorities because of the potential of death and disease from water related diseases… [F]rom 1900–1970, U.S. death rates due to various water-related diseases – dysentery, typhoid, paratyphoid, other gastrointestinal disease, and malaria – declined by 99.6 to 100.0 percent.” Source: Figure 13 in: IM Goklany, “Have increases in population, affluence and technology worsened human and environmental well-being? ” Electronic Journal of Sustainable Development, vol. 1, no. 3 (2009).
There is more extensive discussion of these in IM Goklany, The Improving State of the World: Why We’re Living Longer, Healthier, More Comfortable Lives on a Cleaner Planet  (Cato Institute, Washington, DC, 2007).
The warnings of Ehrlich and like-minded environmentalists had nothing to do with setting in motion action on air and water quality. To believe this is tantamount to believing that one’s responsible for the sun rise if one shows up shortly before dawn.
In addition to Indur’s high-quality research, another favorite piece of research on this matter for me has long been this 1992 paper in Constitutional Political Economy by Roger Meiners and Bruce Yandle .