A toxic-chemical leak at a Brownsville ammonia plant sent workers running for their lives Monday, exposing the city to deadly Mexican working conditions. 'I smelled pure, concentrated ammonia leaking from one of the tanks, and for a second, I thought I was in the wrong country,' plant foreman Dick Shriver said. 'I mean, my God, Americans work here.' Investigators noted with relief that shortly after the leak, a brisk wind came in from the north, blowing the lethal fumes out of the U.S. 