At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga.
Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus.
Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
I'd likely pick "true" in this case.
In the late 1800s, horses were still used for everyday transport. And horses pretty much went wherever they wanted if it was a paved, cobblestone street or a dirt path. To provide heat in homes and steam power in factories, coal was also used as a cheap fuel by everyone. So as a result, you have chimneys belching smoke everywhere. This was before there ever were safety standards for coal burning other than the the usual "don't stand too close to the boiler/furnace" or "watch out for coal dust" warnings. Factories set up close to or inside cities that burned tons of coal wasn't an unusual thing back then.