In the early 1940s spinach and endive crops in Southern California began turning funny colors—first bronze and silver, then black and dead. After ruling out pests and disease, scientists traced the problem to smog blowing over from nearby Los Angeles. Concerned local officials quickly banned backyard incinerators and capped emissions from industrial plants that burned coal and pumped out smoke. Nothing changed. Crops kept dying, and local air only got worse: Hollywood studios began canceling outdoor shoots, and office workers had to abandon buildings downtown on particularly bad days. To scientists, blaming industrial plants didn't make sense anyway. Smog from burning coal—common in Pittsburgh and London—didn't normally damage crops. Furthermore, as chemical instruments tycoon Arnold Beckman pointed out, smog in those places had a sulfurous smell (like a match) and appeared yellow or black. Los Angeles smog turned the air brown and smelled of bleach instead. But if this wasn't classic coal smog, what was it? No one knew, until a Dutch chemist named Arie Haagen-Smit got fed up breathing foul air.
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