Blood testing has emerged as a sticking point. Specifically, a growing movement of veterans and others, united in advocacy groups with names like Fountain Valley Clean Water Coalition and Need Our Water, are asking the military test their blood for the chemicals, hoping to bring results to their doctors or use them in lawsuits.
Their requests have been denied, and the military says that too little is known about the substances to make the results useful. Instead, it will pay for the C.D.C. to start yearslong population-based health studies in some communities.