Well some of it is what your current standard is. Replacing the horse, which puts feces on the road (albeit less smelly than human feces, still really bad in the quantity of a city's traffic), with the automobile, was actually a great improvement in the environment. We don't think of it as such, because we never saw horses in the quantity that a modern city has of automobiles. But what kind of toxic sludge we would have gotten from that much horse manure in a city is difficult for the modern mind to imagine.

Similarly, the environmental impact of coal, when it was the dominant method of heating a home, was not in some decades-off global warming, it was in things like the London Fog (https://en.wikipedia.org/wiki/Pea_soup_fog), a pretty horrific environmental situation. Moving to non-coal methods of heating the home (which he mentions) is a big environmental improvement.