Drywall imported from China may be corroding copper pipes and electrical wiring in dozens of Florida homes and giving their inhabitants chronic respiratory problems, say state officials. The problem first surfaced last summer, when public health workers in Sarasota County began looking into complaints of foul odors and failing air conditioners in a handful of houses built between 2004 and 2006. The initial inquiry quickly focused on the homes’ drywall, which appeared to be emitting sulfur-based gases that interacted with the copper in air-conditioner evaporator coils.

Most drywall used in the U.S. is domestically produced. But during the construction boom that followed Hurricanes Wilma and Katrina, when drywall prices spiked and supplies were scarce, suppliers began turning to sources in China and Mexico to meet demand. In 2006 and 2007, demand for gypsum board in the U.S. peaked at 65.7 billion square feet,...

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