Dave Carew was going on vacation. But first, he had some tabling to do. It was Thursday, two days before the Fourth of July, and Carew, a UPS worker of 13 years, had set up an information booth with pamphlets and thermometers outside the company’s customer center in the north Bronx. His goal was to catch workers on their way in and out of shifts and educate them on how to stay safe when it’s blist...