Most people recognize the word "gypsum" as being the generic name for wallboard or drywall, and that’s because these boards are actually filled with the rock, gypsum. Yet, with so many homeowners in the southern states becoming ill and watching their homes crumble, the latest controversy is how the gypsum wallboard could rot so quickly and become poisonous.


Gypsum in its natural state is a mineral known as calcium sulphate dehydrate, and it’s found in a crystalline form in sedimentary rock formations and on the bottoms of lakes. The mineral is mined or quarried and then crushed into a fine powder and heated to about 350 degrees F in a process called calcining, which separates the chemically combined water from the base. The base is then used for gypsum plaster in wallboard and other materials using gypsum. Gypsum is also referred to as plaster of Paris and was originally generated to use in place of expensive plaster.

Toxic Drywall

In the spring of 2009, CBS News began an investigation in response to complaints that some imported Chinese drywall used in the construction of residential homes was giving off high levels of sulphur, causing copper piping and electrical wires to corrode. In their report, they state that more than 2,000 Americans across the country had become sick due to the sulphur gas leaks in “bad drywall” and that more than 60,000 homes were affected. They concluded that the problem began during a building boom in 2003 and 2004 when the United States was not able to keep up with the demand for wallboard and imported 500 million tons of it from 20 companies in China.

Gypsum Poisoning

Anaerobic bacteria is a common bacteria that can exist in gypsum that isn’t properly processed. When the gypsum becomes damp, the bacteria works with the oxygen in the water and converts the calcium sulphate into calcium sulphide, which produces a poisonous gas called hydrogen sulphide. This gas releases a repulsive odor similar to that of rotten eggs, but the dangerous health issues can begin long before the smell becomes obvious.

Effects of Gypsum Poisoning

The hydrogen sulphide in the gypsum can affect the respiratory system, trigger a skin irritation and rash, and cause inflammation of the eyes. Prolonged exposure will become a serious health hazard and includes symptoms beginning with shortness of breath and wheezing, and leading to breathing failure, coma and even death.

How to Avoid Gypsum Poisoning

Before purchasing drywall for building, get confirmation that the product is original gypsum drywall and not a substitute. You can even have a small piece analyzed for authenticity defining the quality of the gypsum used. As well, the chalk substance in original drywall is very white and is crisp to cut and work with, whereas the color of contaminated gypsum in drywall is light gray and crumbles easily when it’s being cut or screwed onto the wall. Some contaminated drywall has a faint odor of sulphur, but others have no obvious odor at all. When in doubt, have it checked and don't take risks with your health.

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  • Cartoon illustration of a bottle of poison, on a cedar panel. image by samantha grandy from