The link between the sentences “Residents didn’t think much of it” (lines 4 and 5) and They do now is one of cause.

They saw the dust, of course. It was hard to miss. It settled on their swing sets, their picnic tables, their windowsills — a film of dark gray grime. Wipe it away one day and it would be back the next. Residents didn’t think much of it.

Now, many mothers forbid their children to play outside. The school bus picks up some students at their homes so that they don’t have to wait on the corner. Parts of several streets are closed to pedestrians. Danger, the signs warn. Too much dust.

After a century in the shadows of the nation’s largest lead smelter, this modest little river town has awakened with a jolt. Residents learned last month that the dust they have brushed off as a nuisance all these years may have poisoned their homes, their playgrounds — and their children.

An Unknown Number of ‘Leaded’ Children. “Sprinkled over the grass is gray dust”, Jordan-Izaguirre said. “That gray dust is lead”.

And lead is poisonous, especially for young children. Those who absorb too much as they are developing can suffer side effects ranging from stomachaches to learning disabilities to stunted intelligence.