It was raining the other day, and there was this curious milky substance running down the curbside gutter. I followed it back to the source: the road construction sign.

The back of the sign is painted white, and in the rain the paint just washes off.

I wondered if maybe the sign had anti-graffiti treatment on the back, so the paint would not stick.

In the meantime, what does all this while paint do to our sewers?