Drywall is also called gypsum board, sheetrock, plasterboard, or more generally, wallboard. We are going to look over the types and brands, and which chemicals they contain. Which ones have the least toxic additives, don’t offgas, and are the healthiest choices.
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What is Drywall Composed of?
The main ingredient in drywall is gypsum, so let’s start there and look at the health considerations of gypsum. There are two types of gypsum:
Natural Versus Synthetic Gypsum
Natural gypsum is a product mined from the earth. Synthetic gypsum is made from the byproduct of power plants, also called FGD gypsum. They are both technically gypsum.
Unless a product specifically states they use natural mined gypsum, it is exceptionally difficult to track which brands use which type, or if they use a mix.
- 30% of all drywall in North America is synthetic
- USG, the largest drywall manufacturer, has 21 drywall plants. 9 of those only use synthetic. 6 use a mix of the two source
What Else is Drywall Made Up Of:
- Drywall is 70-90% gypsum (synthetic, mined or mixed)
- 10% paper, on the paper-backed types
Other additives that may be included:
- Cellulose fibers (in monolithic drywall)
- Fiberglass fibers (fiberglass is in X and C types, and fiberglass backed drywall)
- Finely ground mica crystal as an accelerant
- EDTA or other chelating agents
- Boric acid/borates
- Wax like paraffin or hydrocarbon, or silanes to hinder water absorption (on the greenboard types)
- Potassium sulfate
- Sodium sulfate
- Vermiculite (in Type C fire resistant drywall)
- EVA as an adhesive
Does Synthetic Drywall Contain Mercury?
Both synthetic and natural gypsum contain low amounts of mercury. It is regulated by the UL standard (ULE 100).
How Much Mercury is in Drywall?
The amount of mercury in synthetic gypsum varies depending on the power plant it came from (source).
It is also a trace metal found in natural mined gypsum. One study found the amounts were 0.92 ng/m2-day for natural gypsum wallboard and 5.9 ng/m2-day for synthetic gypsum wallboard. This resulted in mercury levels in the rooms that were below the background levels normally found indoors and within or below the levels found in outdoor air (source).
Therefore, mercury in drywall has not been a concern of mine. If you wanted to avoid all gypsum board you would be looking at alternatives like MgO board, tongue and groove wood (not allowed by all codes due to fire risk), or plaster and lath (wood or metal lath).
Or, you could minimize the amount of mercury by going with natural gypsum.
USG, Georgia-Pacific, CertainTeed and National Gypsum are the main producers of gypsum board. These are all easy to source at building supply stores and through contractors. The gypsum could be natural, synthetic, or mixed, and it’s very difficult to find out which drywall line contains which type of gypsum.
1. Natural Gypsum
National Gypsum makes gypsum boards that are VOC-free (the paper-backed ones). This brand tends to use natural gypsum.
Their standard line is the regular Goldbond. LITE may also work well for sensitive folks. More on “light” drywall below. The type X is a fire-rated drywall, it contains fiberglass.
You can source this through your contractor’s suppliers. You can get a test sheet at Lowes.
The use recycled paper to back the drywall (like the other major brands).
2. USG SheetRock
This is the largest drywall brand and the easiest to source. The SDS sheets claim 0-VOC. They also have GreenGuard Gold certification, which I discuss more below.
The “regular” drywall should contain the least amount of additives. They use recycled paper backing and facing, but there should be no mildewcide, fiberglass, or other major additives.
USG Sheetrock Ultralight – I have been happy with their Sheetrock Ultralight, I did not pick up any offgassing or moldiness in the paper. Although we don’t know what the blowing agent is (it could be air), I would feel comfortable using this one in my home due to my own testing of it. This is my go-to brand that I specify.
This one is inexpensive and easy to find. You can get it at Home Depot or through your contractor.
USG Firecode X – Research that a very sensitive client revealed that USG was the cleanest gypsum on the West Coast (as it contained more natural gypsum). Though these things change over time, and that same brand could be made in a different factory on the East Coast.
It does not contain a flame retardant, it does contain glass fibers (fiberglass). More on type X below.
Georgia-Pacific Gypsum boards are all GreenGuard Gold Certified. Their exact VOC levels are not listed on the SDS.
Like the other brands, they have a “standard” line which is what I would recommend as the safest bet. The “light” can be considered as well.
GP DensArmor Plus is the most popular fiberglass-backed drywall. No paper here. They recently made a statement that the Dens line is treated with biocides.
CertainTeed Gypsum boards claim zero-VOC (no reportable VOCs), and they have GreenGuard Gold certification.
They have all the same categories of drywall types as the others.
Should You Use Paper-Backed or Fiberglass-Backed?
Many drywall companies use recycled paper which some folks are reluctant to use in their homes. One study showed that paper is already full of mold spores (source). The other concern is that if it gets wet it will mold faster than other materials.
If that is a concern of yours, I would check out the fiberglass-backed drywall and see if that is tolerable for you. Fiberglass is not totally odorless.
If it isn’t, keep in mind that you should not have moisture or condensation behind your wall if your wall is designed and built right. If you have a big leak you are likely to find that quite quickly. I would not rule out paper-backed drywall, personally.
Another type of drywall is called monolithic drywall (pictured above)- no paper and no fiberglass – such as the USG Fiberock line.
It does not have a backing, instead, it contains cellulose fibers dispersed throughout the gypsum. This is a less common type. If you have chemical sensitivities you should test it out yourself if you rule out the other two types. This is my top pick for the type of drywall to use on the bathroom walls (not behind tiles, just the walls).
You do need to skim coat this type of wallboard (same goes for fiberglass backed).
Behind wet areas, concrete backer board should be used (not drywall) – that is discussed in the post on bathrooms.
Costs? Paper-backed drywall is the least expensive type, followed by fiberglass-backed, and then monolithic.
Types of Drywall with Special Properties – Which Chemicals are Added?
1. Fire-Rated Drywall
Type X drywall means it meets requirements for fire codes (that could be required in certain rooms of a house). This type contains glass fibers, is denser, and is 5/8th thick (regular drywall is ½ inch).
It is 10-20% more expensive than regular drywall.
Type C is another type of fire-rated drywall, with a higher rating than type X. It also contains fiberglass and a form of vermiculite. It is more expensive than type X and may be specified for certain areas.
2. Drywall that Reduces Formaldehyde
CertainTeed’s AirRenew (GreenGuard Gold), claims to soak up formaldehyde. However, it also contains a biocide.
It is a little harder to source than the ones above. In Canada, you can find it at Lowes. Some have reported an odor with this one that might indicate that an additive used to soak up formaldehyde might not work for everyone.
This patent might be related to this brand.
3. Light Drywall
The major drywall companies all have lines that are lighter in weight, and these are very commonly used in construction. We don’t know what is added to light drywall that makes it light.
From my testing of it, I did not find that it had chemical offgassing, but we don’t know what the blowing agent is – it could be air or something that dissipates quickly (source).
I did well with USG Sheetrock UltraLite, and I don’t suspect a toxic blowing agent.
Borates are likely to be found in light drywall (source). The SDS will sometimes list borax.
4. Mold Resistant Drywall / Green Board
Both the monolithic (homogenous) drywall and fiberglass-backed types are less prone to going moldy (or at least to going moldy as quickly) compared to paper-backed drywall.
Fiberglass-backed drywall is promoted as more mold-resistant, but all of the brands I have looked at including the Dens line do contain a mildewcide.
If it is labeled as “mold-resistant” and is paper-backed then you can expect a biocide.
Paperbacked brands with mildewcide in them include:
- Georgia-Pacific’s ToughRock Mold Guard -doesn’t disclose biocides but does disclose paraffin wax, polyvinyl alcohol, and poly(methylhydrosiloxane) which are moisture resistant additives (HPD)
- Certainteed’s M2Tech – doesn’t disclose biocides but does disclose paraffin wax, polyvinyl alcohol, and poly(methylhydrosiloxane) which are moisture resistant additives (HPD)
- National Gypsum Goldbond XP – as of 2023 the biocides are undisclosed but in the past I found info that it was treated with thiabendazol, azoxystrobin and fludioxonil (there’s also a European patent for these three chemicals used in drywall)
- USG Sheetrock Mold Tough line – treated with sodium pyrithione (source)
- Pharos also lists multiple sources for the use of sodium pyrithione (source)
“Green board” is a generic term for green-colored drywall like these that have biocide treated paper and are meant for areas with more moisture.
GP’s ToughRock Mold-Guard, American Gypsum’s Aquabloc, and Sheetrock Mold Tough are green board. Purple drywall by National Gypsum is similar.
Additional Health Concerns with Drywall
It is not best practice to use green board (including the purple) behind tiles that get wet.
Best practice in this area is to use concrete backer boards with the Schluter system, or, Schulter or WEDI foam boards, discussed in this post on bathrooms.
If you want to create a mold preventative shower, Schulter and WEDI are the best systems.
Using green board behind wet tiles can lead to mold if there is moisture. They also contain added mildewcides, so I prefer to avoid these types of drywall.
Sulphur Emitting Drywall
The “Chinese Drywall” debacle is the best-known case of a major problem in the drywall industry. Between 2001 and 2009 some drywall offgassed sulfur to the point of causing major problems.
There have also been lawsuits against American-made drywall, but they were dismissed.
I have not seen any issues with sulfur and drywall lately.
In every industry, these kinds of problems do crop up from time to time. Those very sensitive should use their own reactions to guide them. Drywall should never smell like sulfur, and if you react to it that won’t be good for you.
Those who are healthy or less sensitive should go with well-respected brands and do the best you can with the research that we have. Made in America may be better, but is no guarantee that there will not be problems.
The problematic drywall also contained strontium.
When drywall is cut and when joint compound is in dust form (straight out of the bag or after sanding), silica, the same substance that glass is made of is, is harmful to breathe in.
Silica is perfectly safe when in solid form.
Be sure to take great caution when mixing up drywall mud, when cutting drywall and when sanding the mud.
Use an N95 mask or better when around the dust.
The dust is very fine and difficult to remove, I have seen it in builds that are 2 years old. It clings to the wall so you have to clean it very thoroughly.
Make sure the central HVAC is off when drywall and drywall mud work is being done, there should never be drywall/silica dust in your ducts.
Products containing silica dust/quartz will have a Prop 65 warning, keep in mind it’s safe when in solid form.
Should your Drywall be Certified – GreenGuard Gold or UL?
The only benefit to a GreenGuard Gold product is it might catch these unusual problems with offgassing that have cropped up – either sulfur or formaldehyde.
More than a decade ago, some drywall did test positive for formaldehyde, in that sense, GreenGuard Gold is the best certification for this case, as it ensures the VOC levels are extremely low, the same as outdoor air. More details on GreenGuard levels in this post on certifications.
Those who do not want to over-research should go with a big brand Greenguard Gold line that does not contain mildewcides. National Gypsum Goldbond if you want natural mined gypsum.
Drywall should be zero-VOC, and in theory, does not give off formaldehyde at a detectable level.
UL 100 is somewhat helpful in that it regulates mercury, but I expect all drywall to have extremely minuscule levels of mercury.
For drywall mud (spackle/joint compound), drywall tape, and mud for textured walls see my dedicated post on this topic.
Non-Toxic Drywall Mud
Corinne Segura is a Building Biologist Practitioner with 8 years of experience helping others create healthy homes.
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2) The Spruce
3) SDS sheets for all the major brands
5) Pub Med
8) The Spruce