Blog Post

Gypsum Board: Are Our Walls Leaching Toxins?

By any name--drywall, wallboard, or plasterboard--gypsum products may not be as innocent as we once thought.

Drywall, which makes up 15% of demolition and construction waste, leaches toxins and releases hydrogen sulfide gas in landfills.

Virtually ubiquitous in our buildings, gypsum board is widely seen as an innocuous building material. However, in the last decade, Chinese drywall has been linked with indoor air quality problems, while concerns have cropped up around waste from coal power plants and its links to drywall.

Domestic manufacturers are quick to point out that gypsum board manufactured in the U.S. has not been linked to indoor air quality problems, but potential leaching of heavy metals and biocides included for mold resistance are among the issues that need to be addressed more thoroughly by the gypsum board industry.

Synthetic gypsum and mercury

Synthetic gypsum is created from a byproduct of flue-gas desulfurization (FGD), a process coal-fired power plants use to limit emissions. Although the chemical process that captures FGD gypsum is different from the physical collection of fly ash and bottom ash, which is more likely to pick up heavy metals as a matter of course, mercury and other heavy metals are showing up in synthetic gypsum--and, as a result, in our buildings.

In 2010, the U.S. Environmental Protection Agency (EPA) released a study of total content and leaching values of heavy metals in synthetic gypsum, which found that these chemicals could have leaching values of up to 550 times the level for safe drinking water. Total content, on the other hand, never exceeded a measurement of 100 ppm--a difficult feat considering that 100 ppm is the threshold for disclosure in the most rigorous green chemistry programs. Further, gypsum board commonly achieves indoor air quality certifications, such as Greenguard Children & Schools, suggesting that drywall is not a problem for indoor environmental concerns.

Gypsum becomes poisonous gas in the landfill

However, when drywall reaches landfills--and it does so in vast quantities, as it constitutes about 15% of all construction and demolition debris--it can leach these toxic chemicals into groundwater. And in the anaerobic conditions of landfills, bacteria convert gypsum into hydrogen sulfide, a poisonous gas.

Unfortunately, post-consumer gypsum board is commonly diverted from landfills to be used as a soil amendment in agricultural settings. If we have restrictions to prevent these toxic chemicals and heavy metals from being spewed into the air by power plants, is it really a good idea to add them straight into our soil?


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Fungus among us vs. biocides on our insides

As if heavy metal content weren't enough, biocides are commonly used in mold-resistant products because paper-faced gypsum can develop mold if not installed properly. When gypsum is used as a soil amendment, moisture in the soil causes these toxic chemicals to leach into the earth as well.

Raising the standard for drywall

Fortunately, the industry is beginning to address these issues. Steps are being taken to develop an Environmental Product Declaration (EPD) for gypsum board (see "The Product Transparency Movement: Peeking Behind the Corporate Veil," EBN Jan. 2012). Although ULE's 2010 standard based on life-cycle analysis hasn't had the kind of adoption GreenSpec would like to see, many paths toward healthy building materials--and healthier gypsum board in particular--are being explored.

Buyers can use market pressure to encourage this shift--and avoid including toxic building materials in your building projects--by following these steps:

  • Choose domestic: Regulations in the U.S. maintain minimum safety standards for gypsum board, and domestic drywall has not (yet) been linked to the Chinese drywall debacle.
  • Avoid waste: Look for gypsum products with post-consumer recycled content, and avoid waste during drywall installation at the construction site. GreenSpec lists domestic manufacturers that have made strides in post-consumer content.
  • Avoid indoor air quality problems: Select Greenguard- or ULE-certified gypsum board to ensure a healthy interior. GreenSpec lists domestic manufacturers that are certified to indoor air quality standards.
  • Specify inert products: Wet paper-faced drywall is a perfect medium for mold growth, making any biocides included in drywall for mold prevention just a Band-Aid. If you're serious about mold prevention, particularly in settings or locations (like the first floor in a flood-prone area), specify non-paper-faced drywall, like the fiberglass-faced products listed in GreenSpec.

Keep your eyes open for new data in the drywall industry. Send us any tips you might have, and let us know your opinion in the comments below.

Published March 14, 2012

(2012, March 14). Gypsum Board: Are Our Walls Leaching Toxins?. Retrieved from

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March 19, 2012 - 11:31 am


Drywall can be recycled both into new drywall and into other products. However, recycling drywall that has been used runs into some difficulties, such as removing nails and lead paint, if the drywall was painted before 1978. Drywall is often recycled into soil amendment and other agricultural products, which doesn't solve the problem of keeping the toxic chemicals and heavy metals out of our soil.

Drywall not used at a construction site, however, can be easily recycled by gypsum board manufacturers, and it counts as post-consumer recycled content. Drywall recycled in this way counts for the majority of post-consumer recycled content in gypsum board.

March 17, 2012 - 12:46 pm

can drywall not be recycled into new drywall, or other products?

March 15, 2012 - 3:43 pm

For those inclined to "drill, baby, drill", we could open up the White Sands National Monument for gypsum exploitation. The white sand dunes are clean, pure gypsum and there is ostensibly enough for 1,000 years of US gypsum production (and it's already been memorialized in Antonioni's Zabriskie Point, so there's no need to keep it on the ground). Then we could ship the wallboard across the country with Alaskan north slope oil, or Canadian tar sands petrogunk, or hydrofracked natural gas.

March 15, 2012 - 12:16 pm

Robert and others, you may be interested in reviewing some of the plant-by-plant toxicity and other information on drywall available in the Pharos building product library. 36 different products, including those from various specific plants, are scored.

March 15, 2012 - 11:42 am


I can't say for certain whether or not there are domestic drywall products that don't contain any synthetic gypsum, but there are certainly many choices of products that contain single-digit percentages of synthetic gypsum.

Synthetic content varies from product to product, and also from manufacturing plant to manufacturing plant. While about half of gypsum today is synthetic gypsum (and that number is rising) as plants are built next to power plants instead of gypsum mines, I'm sure if you look around it wont take long to find a plant close to you that offers natural mined gypsum instead of synthetic gypsum.

Be aware, though, that natural gypsum comes with a similar set of concerns, as mercury content has been found in natural gypsum, and the mining process can be very destructive.


March 15, 2012 - 9:47 am

It's certainly a good idea to be aware of possible sources of heavy metal, especially mercury, contaminants. that I would assume is more important than hydrogen sulphide in the long run. However I'm not sure that it makes sense to villainize a building material based on the possibility that something might happen if it goes to the landfill. My understanding is that landfulls in the Us have liners and are capped and monitored, and that much worse things than drywall go into them. Surprised to see fiberglass reinforced drywall touted as an alternate, that is a pretty nasty material IMO. I've been saying for years that fiberglass is the next asbestos; hopefully I'll be proved wrong. But installing that stuff is not good for the skin.

March 15, 2012 - 12:35 pm

If the FGD Flue-gas desulferization products don't get integrated into drywall, Where does it go?
At least if we integrate it into drywall we are reducing the effect of virgin gypsum production.
the indoor air quality issue seems farely small if we can rely on Greenguard.
Yes eventylaly it will get into the water and soil.
But the solution might actually be to reduce the coal fire electricity production in the first place

March 14, 2012 - 5:41 pm

A good piece - an long over due look at drywall. Some other points of interest
1 - According to CalRecycle some landfills in Canada would take drywall waste because of concerns over hydro sulfide. .
2- Jim Vallette wrote an excellent piece about mercury in drywall on the pharos site -

March 14, 2012 - 10:00 am

Lloyd, most plaster walls today are built up on gypsum backing board (blue board or rock lath).

March 14, 2012 - 8:26 am

I never understood why people called them drywall walls, when they are really paper walls, with little hairy dust-catching fibres. the Fibreglass is not much better. Time to return to good old lath and plaster, with a lovely smooth finish that takes a coat of paint properly, without a tape line every four feet. It doesn't even cost that much more to do.

March 14, 2012 - 7:58 am

Is there domestic drywall that does not contain synthetic gypsum from FGD? And, does only greenboard (MR - moisture resistant) drywall contain biocides?

March 14, 2012 - 7:53 am

I usually scan the headlines and read the content later but decided to read the entire blog now. And boy, am I glad I did! This is yet another issue to keep in mind when dealing with drywall. Indeed, ground contamination is just as important, and I'm glad Building Green addresses this issue. It also points to the need to be vigilant. Placed in this context, conventionally built buildings are overvalued. Do we know the leaching timeframe for installed drywall? Does it diminish over time, or is it constant?