Miami, Florida (CNN) -- An extended study of the long-term effects of exposure to defective Chinese drywall on people whose homes contained it is not necessary, the U.S. Centers for Disease Control has determined.
That decision was made, according to the CDC, because the symptoms that people are suffering from are self-reported and too general and exposure levels are not available -- meaning a scientific study would take many years, require enormous resources and is unlikely to yield useful results.
"...The best scientific evidence available to us today does not support undertaking a long-term health study," said Bernadette Burden, CDC spokeswoman.
Residents of 42 states, Puerto Rico and America Samoa have complained that Chinese drywall, imported into the United States, have made them sick with chronic sinus and upper respiratory problems, nosebleeds, migraine headaches and other ills. Their sickness, they say, appears to go away once they move out of their homes.
The U.S. Consumer Product Safety Commission has determined that the drywall emits extraordinarily high levels of hydrogen sulfide, which gives off a pungent rotten-egg smell inside the homes. The sulfur inside the drywall has corroded metallic objects in homes and has caused electrical wiring, appliances and air-conditioning systems to mysteriously fail.
But "the levels of sulfur gases found in environmental samples were generally in low parts-per-billion or parts-per-trillion levels," Burden said. "These levels are so low that other confounding factors would overwhelm them in a study."
"It would be extremely difficult to tie (the levels) to health effects. The sample size would not give enough statistical power -- at least 10,000 participants would be needed," she said.
However, the news that the CDC will not investigate the health effects further does not sit well among some homeowners who have the defective wall product.
Eleanor Aguilar had to move out of her Lauderhill, Florida, townhome after she believed her walls made her sick with migraines, sinus trouble and nosebleeds -- symptoms that made living there unbearable.
"I'm disgusted. This is something no one has ever had before. Are you gonna put your head in the sand?" she wondered.
CNN has spoken to many homeowners who wondered what the drywall could be doing to their health after they saw the insides of their homes being corroded and their air-conditioning systems, stereos and computers dying.
Allison Grant is a Florida attorney who represents about 1,200 people with co-counsel Bob Brown. Their clients claim to be plagued by the drywall, which has made them sick, and which they say has caused their property values to plunge.
"I am shocked that the CDC has determined at this early stage that no further studies are warranted," Grant said. She maintains that hundreds of her clients have suffered adverse health effects, and several have been hospitalized for infections and sinus surgery.
"While I certainly hope that there are no long-term health effects, the CDC's decision sends the message that any health effects are inconsequential and not worthy of further study," she told CNN.
So far, the U.S. Consumer Product Safety Commission has documented about 4,000 homes with the problem, but they believe the numbers are greater. The drywall was imported into the Unites States in 2005 and 2006, when a shortage of building materials due to very active hurricane seasons, as well as a home building boom, caused America to import more drywall from China.
The commission is recommending that homeowners remove the drywall, gut their homes and replace the electrical wiring. But that costs thousands of dollars and is not covered by homeowners' insurance.
So thousands of people have become part of a nationwide class-action lawsuit, based in Louisiana. A federal judge has already ruled the Chinese drywall companies are liable, but that order is being appealed.
One of those companies, Knauf Plasterboard Tianjin, has entered into an agreement with plaintiffs to begin gutting and rebuilding 300 homes as part of a pilot program.
However, the company said the CDC's decision against further investigation underscores its own findings that do not link the drywall to long-term sickness.
"We're obviously aware of those reports, but haven't seen any empirical evidence or studies that link this to the drywall," said Knauf attorney Greg Wallance.
Wallance said the company's renovation program should give confidence to homeowners.
"This should address the concerns the homeowners have, by getting the drywall out," he said.