By Aaron Kessler


Published: Thursday, January 29, 2009 at 1:00 a.m.
Last Modified: Thursday, January 29, 2009 at 8:42 a.m.
The environmental consulting firm hired by Miami-based Lennar Corp. has concluded there is little doubt that Chinese-manufactured drywall installed during the housing boom is the cause of the corrosion that homeowners say is eating away at the guts of their homes.


Click to enlarge
Owners of affected homes in Manatee County’s Heritage Harbour neighborhood say coils, wiring and piping have turned black and there is a foul odor. Order photo
STAFF PHOTO / THOMAS BENDER
Key Documents:
Drywall health, impact study (PDF - 37573kb)
Air-conditioning coils have turned black and failed, along with wiring, piping and even silver jewelry.

But Environ International Corp. said it found no chemical levels that would pose a danger to occupants.

"We have definitely identified that a combination of sulfide gases are the cause of the corrosion of the coils," said Robert P. DeMott, managing principal of Environ. "The substances we've found are well known to cause that kind of corrosion."

Foul odors reported by people living in the homes may also be caused by the combination of sulfur gases being released from the drywall, DeMott said.

But DeMott said Environ's investigation of the air inside 79 affected homes in Southwest Florida concluded that no sulfur chemicals were present at levels dangerous to human health.

On Wednesday, Lennar sent a 765-page document to the Herald-Tribune that details the results of Environ air quality tests performed last year.

Air samples were taken in one-liter bags by Environ workers in homes built in four Southwest Florida counties, including Sarasota and Manatee. The company typically took two indoor samples and then one from outside, and the bags were sent to a testing lab run by Air Toxics Ltd. for analysis.

The results found three sulfide gases: carbon disulfide, carbonyl sulfide and dimethyl sulfide.

Hydrogen sulfide, a particularly dangerous compound with a characteristic rotten-eggs smell, was not found in Environ's air tests, but it was found in previous testing that the company conducted on the Chinese drywall itself, the report says.

The previous Environ studies that examined the corrosion have not yet been released, but DeMott said that the hydrogen sulfide found in the previous tests also was far below the level where it represented a health risk.

Hydrogen sulfide was found in separate tests conducted in 2006 by Knauf Plasterboard Tianjin Co. Ltd., the Chinese manufacturer of some of the problematic drywall.

Knauf's testing of about a half-dozen Florida homes found levels of the compound ranging from 2.3 parts per billion to 4.1 parts per billion in all of its samples, including ones taken from non-affected houses or from outside. Phillip Goad, the toxicologist hired by Knauf, concluded in his own report that "the homes built with the Knauf Tianjin product did not have elevated levels of hydrogen sulfide."

Environ's air samples were tested with a minimum threshold of 4 parts per billion by the Air Toxics lab, so anything under that level would not show up at all. In a few cases, an even higher threshold of 6 parts per billion was used. DeMott said the lab was asked to test for hydrogen sulfide at the smallest concentrations possible.

"We believed they could reliably measure down to four," DeMott said. "When you go down further, you lose some certainty in how accurate your results become. We chose then to get a more reliable number."

In 2007, the federal Agency for Toxic Substances and Disease Registry, know as ATSDR, set its guidelines for chronic residential exposure to hydrogen sulfide at 20 parts per billion.

"The critical answer was whether there was 20 parts per billion," DeMott said. "So we were confident that a level of a four or a six was much lower, and therefore if hydrogen sulfide was not found at even those levels then it was not a concern for people's health."

DeMott said it was not unreasonable to conclude, however, that smaller levels of hydrogen sulfide and other sulfur compounds could still result in the foul smells residents have reported.

The ATSDR-published medical management guidelines for hydrogen sulfide state the chemical can be detected by smell by some people once it reaches just 0.5 parts per billion.

Michael Foreman, head of Sarasota construction consulting firm Foreman & Associates, is unconvinced that the gas coming from the drywall poses no threat.

"If that's the case, then why is everybody getting sick?" Foreman said. "Why do they all have the same problems? If it's caustic enough to eat up the components in the house, then I can only imagine it must have some effect on your body. If it's corrosive enough to eat through copper coils, what is it doing to a mucus or a membrane. Those metals are more durable than your lungs, you would think."

Testing air samples is notoriously difficult, Foreman said.

"It's very delicate," he said. "The tests can be affected by the volume, how the sample was taken, the location, all kinds of factors. You can have the same test run by different groups at the same time and get two different results."

To date, Florida health officials have logged more than 50 complaints stemming from the Chinese drywall.

Lennar has said 80 of its homes in Sarasota, Manatee, Lee and Collier counties have Chinese product installed and another 40 may have it. Two more homes have been identified in Miami-Dade.

Lennar's Heritage Harbour development in Manatee County is particularly affected, with nearly the entire street of Montauk Point Crossing in the Lighthouse Cove neighborhood evidencing the problem.

The first town house also is being investigated in Lighthouse Cove, which would mark a spread of the problem beyond just single-family homes.

Residents of the nearby development Greyhawk Landing, where Lennar also was the builder, have reported instances of Chinese drywall.

http://www.heraldtribune.com/article...ril_in_drywall