The Myth of Polyacrylamide Hydrogels:
"Polyacrylamide hydrogels are environmentally safe substances that reduce irrigation needs"
The Myth
With a significant drought looming on the horizon for the Pacific Northwest, those of us whose business or pleasure includes landscape plants are understandably concerned with water issues. In response, the dot-com websites are full of products promising to reduce water usage in the landscape.
Prominent among these products are hydrogels, which have been used successfully by the landscape industry to reduce transplant shock and increase containerized plant growth. These hydrogels, sometimes referred to as root watering crystals or water retention granules, swell like sponges to several times their original size when hydrated. Water is then released slowly to the surrounding soil, reducing the need for irrigation.
Once considered to be a professional nursery product, hydrogels are increasingly popular with homeowners who add them to vegetable gardens, container plants, annual beds, lawns, and perennial landscapes. The most commonly available are polymers of acrylamide and potassium acrylate. These polymers have a longer functional life, perhaps up to five years, compared to other organic hydrogels composed of starch, gelatin or agar. These latter hydrogels are commonly used in cosmetic surgery; polyacrylamide gels are not used for this purpose.
The Reality
My initial concern with hydrogel usage is the public perception that it is a permanent fix. Hydrogels are routinely touted as pH-neutral, non-toxic, environmentally friendly compounds, which they are in their polymerized form. The fact remains that after five years virtually all hydrogel will be depolymerized through natural decomposition processes. The rate of degradation is increased especially in the presence of fertilizer salts (and no, it doesn’t make any difference if these are synthetic or organic fertilizers).
One is then left with the original soil conditions; in a permanent landscape, this can be problematic unless other water-conserving steps are then implemented.
My second, and probably greatest, concern occurred when I discovered that hydrogels are constructed of acrylamide units. When hydrogels break down, they release potassium acrylate and acrylamide. Acrylamide is a lethal neurotoxin and has been found to cause cancer in laboratory animals. It readily passes through the skin and can be inhaled as dust. Unfortunately, the chemical data sheets on hydrogels do not mention the fact that within a few years they will be composed entirely of these acrylamide units.
Since polyacrylamide is defined as “not readily biodegradable” (less than 10% is degraded after 28 days), some sellers of hydrogels actually promote their products as “nonbiodegradable!”
Who is at risk to acrylamide exposure? Workers in the nursery and landscape industry who routinely use hydrogels may become exposed to them as they degrade and become toxic. Homeowners who add hydrogel-containing potting mix to their landscapes or compost piles are exposed. Dogs, cats, and wildlife that come in contact with these substances are at risk. On a larger scale, entire ecosystems are at risk as acrylamide is water-soluble and can easily enter watersheds.
One of the greatest pleasures of gardening is getting your hands into good, rich soil and breathing in its aroma. I believe that the increased, and indiscriminate, use of polyacrylamide hydrogels is an extremely serious hazard to human health and to the environment.
The Bottom Line
• Hydrogels are organic compounds that will degrade after 2-5 years; they are not a long-lasting solution to droughty conditions
• Exposure to fertilizer salts will increase the degradation rate of hydrogels
• When hydrogels degrade, one of the byproducts is acrylamide, a deadly neurotoxin and potential carcinogen
• Acrylamide can be absorbed through the skin or by inhaling; people who have a likely risk of exposure to this compound absolutely require safety clothing and dust masks
• There are safe (albeit shorter-lived) alternatives to polyacrylamide hydrogels, including starch- based gels and others currently used in cosmetic surgery
• There are other environmentally sound ways to reduce water usage and improve water retention of soils than through hydrogels
~ Linda Chalker-Scott, Ph.D., Extension Horticulturist and Associate Professor,
Puyallup Research and Extension Center, Washington State University
You can contact Dr. Chalker-Scott at lindacs@wsu.edu.
http://www.puyallup.wsu.edu/~Linda%20Chalker-Scott/Horticultural%20Myths_files/Myths/Hydrogels.pdf.
Hydrogel crystals
It must be a very old article you are picking up. I believe today you find that the polymer crystals are safe. In fact, the polymer crystals you buy today are similar to those in baby diapers. Just because someone with "Ph.D" in their title decides to write something does not make it true.. it is incredible how many times written articles gets quoted just because of this...
I find polymer crystals very good at establishing small perennials until they develop a large root system and can fend for their own. They also work great when mixed in soil where annuals are planted, such as petunias and marigolds. The years we forgot to add polymer crystals we could not water frequently enough to keep the plants from drying out (and blooms from stopping). When using polymer crystals, I can keep up watering..
kd, I agree with their ability to cut down watering, which is why I was doing a Google search for them.
Here'a another:
ISIS Report, 1 August 2002
Acrylamide In Cooked Foods: The Glyphosate Connection
Recent health alert over toxic acrylamide in cooked foods is linked to glyphosate, Prof. Joe Cummins reveals.
Acrylamide is a building block for the polymer, polyacrylamide, a material well-known in molecular biology laboratories as a gel matrix for resolving DNA fragments in sequence analysis and identifying proteins, both under electric fields. In the world at large, polyacrylamide is used in water purification to flocculate suspended organic matter. Recently the world health organization (WHO) had a closed meeting to review the finding that cooked vegetables had significant levels of acrylamide [1]. The finding received worldwide attention because acrylamide is a potent nerve toxin in humans and also affects male reproduction, and causes birth defects and cancer in animals. The WHO press releases implied that the acrylamide finding was a surprise and that the pollutant probably arose from cooking the vegetables.
Strangely, the WHO releases did not mention the fact that polyacrylamide is a well known additive to commercial herbicide mixtures (25% to 30% solutions) to reduce spray drift and to act as a surfactant [2]. The glyphosate (ie Roundup) herbicides of Monsanto Corporation are of particular concern because the herbicide interacts with the polymer [2-4]. Experiments showed that heat and light contribute to the release of acrylamide from polyacrylamide, and glyphosate was found to influence the solubility of polyacrylamide, so care was advised in mixing the two.
The evidence seems compelling, therefore, that acrylamide is being released from polyacrylamide in the environment, one of the main sources of which is in glyphosate herbicide formulations. Cooking vegetables that had been exposed to the glyphosate herbicide used with herbicide-tolerant crops, or used during soil preparation for normal crops would result in the releasing more acrylamide. Worse yet, additives such as polyacrylamide are designated 'trade secrets' in North America and information on the contents of herbicide preparations are not available to the public.
I am surprised at WHO's feigned ignorance of the polyacrylamide -herbicide connection. WHO should make more effort to consult experts independent of the giant herbicide corporations for a change, so the public could be told the whole truth.
Weiss G. Acrylamide in food: Uncharted territory. Science 2002, 297,27. Smith E, Prues S and Ochme F. Environmental degradation of polyacrylamides:Effect of artificial environmental conditions. Ecotoxicology and Environmental Safety 1996, 35,121-35.
Smith E, Prues S and Ochme F. Environmental degradation of polyacrylamides: II Effects of outdoor exposure. Ecotoxicology and Environmetal Safety 1997, 37,76-91.
Fischer K, Kotalik J and Kettrup A. Determination of acrylamide monomer in polyacrylamide degradation studies by high performance liquid chromatography. Journal of Chromatographic Science 1999, 37,486-94
This article can be found on the I-SIS website at
http://www.i-sis.org.uk/acrylamide.php
Acrylamide in food
Pesticide residues on GE corn and soybeans may be carcinogenic. A chemical component of Monsanto's Roundup Ready herbicide, sprayed on millions of acres of herbicide resistant soybeans and corn, has been linked to increased risks for cancer. Recently the World Health Organization issued a warning that a potent nerve toxin and carcinogen, also linked to birth defects in animals and humans, was turning up in a variety of vegetables.
At first the WHO suggested that the presence of the chemical, acrylamide, probably arose from cooking the vegetables at high heat. Now according to a Canadian scientific expert, Dr. Joe Cummins, another, perhaps even more basic explanation is that the acrylamide in foods is actually a residue of a surfactant, or chemical additive, routinely used to enhance the effectiveness and reduce spray drift of a number of herbicides including Monsanto's Roundup herbicide, the most widely-used pesticide in the world.
According to Cummins, frying foods containing acrylamide residues would then likely increase their concentration even more. This is yet more bad news for Monsanto, who derived 70% of their profits last year from sales of Roundup herbicide. It's also bad news for the animal feed and meat industry, since non-organically raised animals are now ingesting record amounts of Roundup (and acrylamide) residues in the soybean hulls and other soy and corn-based feeds they are consuming.
http://www.organicconsumers.org/monsanto/acrylamide.cfm
Polyacrylamide absorbs up to 400 times its own weight in water. It is used in disposable nappies (diapers) for this reason. It is sold in garden centres for hanging baskets and other houseplant situations where water retention is needed. It seems inevitable that, as the roots of the plant take up water, they will draw polyacrylamide from the soil and incorporate it into their tissue.
As far as I know, polyacrylamide is not permitted in organic farming so a quick test of organic chips, crisps and crispbreads could provide an interesting result.
From http://ngin.tripod.com/170802b.htm
This is very interesting Darius as I just purchased and used these products for the first time. I will check out the product that I have and keep everything in mind for future use.
I am very concerned about anything potentially dangerous that can enter the ground water.
Thanks. I was beginning to feel like The Lone Ranger.
I'm sure we're not alone...maybe some people don't want to think about the possible hazardous effects, but I think we need to.
I get more environmentally conscious all the time. I shudder to think of all the harm I have inflicted on this planet just by myself out of the ignorance of younger years. Things like dumping oil after changing it in my car, heavy use of pesticides (esp, household, I didn't garden then), herbicides and even littering as a teenager.
this is very interesting. I have just started using these and now I am concerned. I saw some organic methods that don't last as long mentioned in the articles, where can I find out about these? Since I am mainly using these for my hanging baskets and annuals anyway, that would work for me.
Rachel
Darius, don't feel alone. I had heard something like this a while back, can't remember where. I used some a couple of years ago, now I'm looking at the alternatives. While I normally go organic on everything and would usually never consider buying Miracle Gro, I noticed that their
"Moisture Control" potting soil depends on coir for water retention. It is a natural fiber that people in the Propagation forum swear by for keeping seedlings moist but not water-logged, so I was impressed. I bought some of the potting soil for some containers and it has done very well. So well, that I have bought more.
Thanks for posting this. People to need to hear about it.
I don't do a lot of container gardening but I picked up a jar of these crystals for a few hanging pots. Now that it seems they might be doing double duty as a rodent killer I will be buying more. Nothing I hate more than an infestation of white rats!