GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Fly Ash health concern

user-894335 | Posted in Green Products and Materials on

I came across some articles regarding fly ash health concerns:

With little kids in a tight house and organic garden in the backyard, I’d rather not use fly ash in concrete even though there is no clear evidence that it actually poses health risk (yet). Since there are toxic materials in fly ash, I don’t want any potential toxic dust in the air/water now or at the end of its life cycle. I think more research is needed and I just don’t want to use it now.

When I told my contractor NOT to use fly ash, he asked me – what else would you like me to use instead? Is there an issue to tell him to only use Portland cement?

P.S. I know Portland Cement uses a lot of energy to reproduce. We have been doing our best to minimize our energy consumptions for many years and will continue to do that.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Martin Holladay | | #1

    In most areas of the U.S., most concrete does not include fly ash, so your contractor's question is surprising.

    You can always call up your local batch plant to get information on different available concrete types. I suspect they will provide you better information than your contractor.

  2. J Chesnut | | #2

    I would ask your contractor to give you the contact information to the company they are ordering the concrete from so you can speak to them directly about the contents of the concrete mix. There should not be any issue to omit the flyash.

  3. Riversong | | #3

    In my experience, fly ash is added to a concrete mix only if specifically requested.

    But, like flouride in drinking water and depleted uranium in artillery shells, it is just one more method for disposing of otherwise toxic and problematic industrial waste materials.

    From: Science In Dispute, Volume 2 (2003) By Lee Ann Paradise, David Petechuk, Leslie Mertz

    Many of the substances in fly ash are known to have carcinogenic and mutagenic effects; and some, such as dioxins, are so toxic that experts cannot agree on a safe level of exposure. In one study, a team of ecologists at the U.S. Department of Energy's Savannah River, SC, Ecology Laboratory linked fly ash with developmental abnormalities (both behavioral and physical) as a result of high levels of heavy metals leaching into the water. For example, affected bullfrog tadpoles and soft-shell turtles had elevated levels of arsenic, cadmium, selenium, strontium, and mercury.

    Although recycling fly ash into building materials may seem to be a viable alternative to disposing fly ash into waste dumps where it can leach into the soil, using a hazardous material in building products is actually waste disposal masquerading as recycling. A fundamental rule of recycling is similar to that of medicine, that is, "First, do not harm." However, the use of fly ash in construction materials is far from safe. For example, some buildings in the United States, Europe, and Hong Kong have been found to have an increase in toxic indoor air contamination which is in direct relation to fly ash that has been used as an additive in concrete to make it more flowable. In a high rise building in Hong Kong, researchers suspect that the combination of fly ash and granite aggregation in concrete causes the building to be "hot" with the radioactive gas radon when the air-conditioning systems are shut down at night and on weekends. As a result, night and weekend workers may be exposed to higher and potentially dangerous radon levels.

    One especially troubling component of fly ash is dioxin, one of the best-known contaminates of Agent Orange, the notorious defoliant used in the Vietnam War. On July 3, 2001, the British Broadcasting Corporation (BBC) featured Workers pouring concrete during the construction of a stadium in Seattle, Washington. ( Photograph by Natalie Forbes. CORBIS. Reproduced by permission. ) a report on its Newsnight program about highly contaminated mixtures of fly ash and bottom ash (the ash left at the bottom of a flue during coal burning) that included heavy metals and dioxin. The mixtures had been used throughout several London areas to construct buildings and roads. Tests showed that the dioxin content of the fly ash was greater than 11,000 ng/kg (nanograms per kilogram), which is much greater than the 200 ng/kg left as a result of the use of Agent Orange. (In fact, 30 years after the end of the Vietnam War scientists still find elevated dioxin levels and birth defects in human tissues in Vietnam.)

    In addition to the many hazardous compounds already contained in fly ash, the use of ammonia to condition fly ash adds another environmental/health problem. Ammonia can be adsorbed by the fly ash with the flue gas train in the form of both free ammonia and ammonium sulfate compounds. During later transport and use of this fly ash, the ammonia can desorb, which presents several concerns. The primary problem associated with ammonia in fly ash is connected with waste disposal, since moisture can cause the ammonia to leach into nearby rivers and streams. However, ammonia desorbing into the air from contaminated fly ash is also a concern with its use in concrete mixtures. During the mixing and pouring of concrete, ashes with high amounts of ammonia may create harmful odors that can affect workers' health. Fly ash also poses a potential health and environmental hazard during storage before mixing, since a strong wind can scatter the fly ash, and rain can cause it to leach into the ground.

    Even if the fly ash were not causing immediate harm to people or the environment as part of a construction material, "disposing" fly ash in the concrete construction materials of a building is a temporary solution at best. Little is known about the leachability of materials made with fly ash. And, if the concrete in a building is a source of environmental health problems, replacement is often not an option. Once a building is constructed, little can be done since there is no proven method of encapsulation to control emissions. In the final analysis, it is bewildering for government regulations to require industries to spend millions of dollars on antipollution devices to capture deadly toxins, but then allow these toxins to be used via fly ash in the construction of office buildings, houses, roads, and even playgrounds.

  4. James Oquin | | #4

    To date, there have been numerous tests on fly ash to determine the leachability of heavy metals. Like natural occurring heavy metal in soil, some are worse than others. The TCLP test is the most commonly used test for determining leachability. The best and most safe place for fly ash is in concrete. When introduced into a concrete mix, the fly ash chemically bonds with the Portland cement and becomes a part of the Calcium Silicate Hydrate (binder or glue) of the concrete. So the impurities are bound together in this process. The wet disposal process of fly ash at the power station is quickly becoming obsolete and utilities are spending hundreds of million of dollars to engineer safer and stronger landfill for Coal Combustion Products that are unable to be used benificially. Fly ash in concrete helps prevent Alkali Silica Reaction which causes internal expansion causing the concrete to crack; Fly ash improves durability by preventing Sulfate Attack from natural occurring or man made chlorides such as de-icing salts; finally, Fly ash help improve concrete strength by forcing the Portland Cement to have a more complete hydration (curing).

  5. rustyjames | | #5

    What about when the concrete containing the flyash reaches its useful life? Then it can be argued that it is a hazardous material that will have to be dealt with.

  6. Michael Chandler | | #6

    My concrete supplier also doesn't automatically add fly ash but is happy to use it for footings or exterior paving for the reasons mentioned above.

    We use it when we can but not in interior slabs, counter tops, or cast fireplace surrounds and the like.

    Seems better to bond it in concrete than leaving it in giant collection ponds exposed to the environment. At the same time, doing all we can to stop expansion of coal fired electric plants and mountain top removal has to be part of our mix as well.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |