About 24,000 homeowners across the nation had mold-related insurance claims unresolved as of December 31, the New York Times reports, citing estimates from a Texas-based homeowners advocacy group called Policyholders of America.

Mold has long been known to cause serious damage to some people's pulmonary systems. But over the last five years concern has exploded.

Last year, according to Robert P. Hartwig, the chief economist for the Insurance Information Institute, insurance companies paid out $2.5 billion in mold-related claims.

Industrial hygiene consultants who specialize in mold investigations are having a field day. This year's American Industrial Hygiene Conference and Expo, in Dallas May 10-15, will be loaded with seminars and speakers on the mold hazard.

The insurance industry has rebelled against the hefty payouts. At the industry's urging, 35 states have allowed insurers to exclude mold coverage from homeowner policies.

The potential for claims is vast - according to the American Academy of Allergy, Asthma and Immunology, 35 million Americans suffer from reactions to mold. That's 12 percent of the nation's population. Texas and California are the two hot zones for mold fever.

Trying to put the issue in scientific perspective, the American Industrial Hygiene Association offers a consumer brochure, "The Facts About Mold," that can be accessed from its Web site - www.aiha.org.