Robert Swain's own health has begun to deteriorate since doing more home inspections. Swain has a recurring cough he still has yet to seek medical attention for. (Phillip Lucas/NYT Institute )

When Stephen Guerra checked the back side of drywall in his 72-year-old mother’s newly renovated home and found that it had been made in China, the mysterious smells and rusted metals in the house suddenly made sense to him.

Guerra’s discovery explained the periodic smell of rotten eggs in the home, the spots of rust covering the metal clock in the bathroom — and perhaps his mother’s illnesses, including a recurring rash that she and her other son, Paul, suffer from.

His mother, Darlyn Guerra, said she also has a corneal ulcer and that even her 5-year-old white Maltese dog, Itsy, has been suffering from a rash since moving into the home, in the Upper Lake Shore area of New Orleans.

Across Lake Pontchartrain in a quiet Covington, La., development, Raymond Hickey, 86, and his wife, Elizabeth, 85, are still waiting for results of home inspections done a month ago by several agencies, including the Louisiana Department of Health and Hospitals.

“They said they’ll contact us,” Mr. Hickey said. The interior walls of their 3-year-old home are now marred by 4-by-6-inch holes cut by the inspectors.

The Hickeys said they already know what the inspection will show.

Since moving into their home, completed in 2006, they have seen electrical cords short out, metal bathroom pipes split open and metal fixtures in the bathroom quickly tarnish and rust, and they’ve both suffered from sinus infections.

If the Hickeys’ suspicions prove right, their home, like Guerra’s, has drywall – the manufactured sheets of plaster used for ceilings and walls – that has been releasing sulfur dioxide gas.

State officials say that such drywall, manufactured in China, has sulfur levels approximately 10 times higher than what United States government standards allow in domestic products. According to court documents, the drywall is made in part from waste products collected from Chinese coal-fired power plants. Air and moisture interact with the sulfur, producing sulfur dioxide gas. The gas is so corrosive that it can turn a bright new penny black in a short time. At both homes, bright copper wires have been doing just that.

According to Patricia M. Williams, an associate professor of toxicology at the University of New Orleans, sulfur dioxide can cause respiratory illnesses, eye irritation and can enter the bloodstream through the lungs. Williams cited a study of volcanic gases, which contain sulfur dioxide, that showed that chronic exposure results in “increased prevalence of cough, phlegm, rhinorrhea, sore/dry throat, sinus congestion, wheezing, eye irritation and bronchitis.”

A number of Louisiana residents – and many other Americans who have done recent renovations – have discovered that the drywall from China that they used can emit high levels of sulfur dioxide. Many of the homeowners are concentrated in areas affected by hurricanes or floods in the Southeast.

“It could be any house anywhere in the United States that had any construction going on basically from 2002 to 2008,” said Robert Swain, a New Orleans home inspector. He said he had to come out of retirement to help his brother, George, president of a local home inspection company, deal with the rising numbers of inspection requests such as Guerra’s.

In Louisiana, most of the high-sulfur drywall is manufactured by Knauf Gips, a German-based company that has plants worldwide, including in China. The company owns a “substantial stake” in USG, America’s largest provider of drywall, according to court documents in a class-action lawsuit filed by the Becnel law firm in Reserve, La., on behalf of Jill M. Donaldson and John Oertling of Pearl River, La., and all other affected homeowners in the state.

Defendants in the case include Knauf Gips, the Knauf Plasterboard Tianjin Co., USG  and its subsidiary Seacoast, and Interior Exterior Building Supply, where drywall for both the Guerra and the Hickey’ homes came from.

Knauf and its affiliates are accused of negligence and knowingly distributing over 10 million square feet of faulty drywall in Louisiana alone through separate domestic distributors. (Knauf Plasterboard Tianjin is known to provide drywall to 50 countries,  the court documents say.)

In the fall of 2006, Guerra, moved into her home from a FEMA trailer parked on her front lawn, and she started noticing metal corrosion months later. She had rushed to move into her unfinished home because of the formaldehyde in the trailer.

Displaced by Hurricane Katrina after living in Chalmette, La., for 58 years, the Hickeys had decided to buy a new home in Covington and spent their life savings on it. The couple has no resources other than the value of their home. They now live on Social Security payments and are grappling with the possibility of having to leave their three-year-old home and move into one of their children’s homes.

The Hickeys said they filed a claim with their insurer, State Farm, and were visited by an agent. Two days later, they said, they received a letter from State Farm saying the company wouldn’t cover any of the damages since the material was installed and State Farm doesn’t cover materials used for construction, or corrosion or rust.

A State Farm representative was not available for comment before deadline.

Complaints over Chinese drywall in Louisiana began in March, and homeowners across the state and country continue to report bloody and runny noses, dry coughs, dry eyes and sinus infections that they attribute to high-sulfur drywall. The Louisiana Department of Health and Hospitals has received about 600 calls on a special hotline set up to deal with the issue, and Senator Mary Landrieu, D-La., has encouraged people to call the hotline to get help.

It is unclear how many separate homes contain high-sulfur drywall, but Senator Landrieu has said the material used in the state is equivalent the amount needed to complete 7,000 homes.

Swain said the number, which he believed could be seriously understated, is based on each house being roughly 2,000 square feet. It doesn’t account for cases like Guerra’s, where only portions of the home have the product installed, and houses much smaller than 2,000 square feet that leave leftover material available for use in additional homes.

“This is definitely the tip of the iceberg, it could get tremendously bigger,” Swain said. “Everything is so new about it, all these problems are all coming up now,” he said, “It’s the new asbestos.”

Not all Chinese drywall is toxic, said Aleis Tusa, director of communications for New Orleans Habitat for Humanity. The nonprofit organization bought 100,000 sheets of Chinese-made drywall in 2007 and once concerns arose, tested the material for 20 harmful compounds. No harmful compounds were detected, Tusa said.

A shortage of American-made drywall that began around 2004 left most domestic contractors looking to China for large amounts of the product. The rush to provide material to those desperate to rebuild in the Gulf Coast occurred federal agencies had no regulations for screening unsafe imported drywall.

“It was selling,” Guerra said of the Chinese-made drywall. “If you didn’t get to Home Depot or Lowes early in the morning, you didn’t get the sheetrock [drywall].”

In 2006, Guerra used her state relief benefits to buy 34 sheets of drywall from Interior Exterior Building Supply, headquartered on Cortez Avenue in New Orleans. She spent just under $600 on the material.

Lee Roy Jenkins, who built some of the homes in the Covington development, including the Hickeys’, bought his material from Poole Lumber, which he said bought its supply from Interior Exterior. He said his liability insurance doesn’t cover the damages to the homes he has built.

Interior Exterior is now involved in 31 lawsuits in Louisiana Federal District Court.

A representative of Interior Exterior Building Supply said he couldn’t comment because of the litigation.

Regulation of imported drywall falls under the jurisdiction of the Consumer Product Safety Commission, which is carrying out an investigation into the materials’ effects on homes and health. An aide to Landrieu said the agency should have prevented the high-sulfur drywall from entering the country. He said the senator has asked the agency to expedite an investigation. She has also asked for increased funding for the agency.

The agency said that as of May 27 it had received 365 reports from people “who believe their health symptoms or the corrosion of certain metal components in their homes are related to the presence of drywall produced in China.” The reports come from 18 states, with the majority from Florida.

“We have visited and spoken to homeowners in Louisiana, Florida, Virginia and other states and experienced the same symptoms they have, seen the blackened appliance coils, and taken reports about children suffering from health effects,” said Scott Wolfson, deputy director of the agency’s public affairs office. “We are committed to providing answers to families and homeowners as quickly as possible.”

Guerra and the Hickeys are waiting for those answers. They gutted their homes after Katrina, less than three years ago, and now say they must completely gut their homes again. The cost of re-renovating Guerra’s home could conservatively be $80,000,   Swain said. And now Paul Guerra wonders whether he was right to rip out the mold-covered drywall after Katrina

“The mold would have been much less toxic.”