Polyacrylamide

[Guest guest]

Polyacrylamide

is

added to soil and pesticides,

it may be a major problem?

Prof.

Joe Cummins /

Department of Biology / University of Western Ontario 8aug02

e-mail: jcummins@...

Acrylamide is a building block for the polymer, polyacrylamide, a

material

used in genetics in molecular biology laboratories as a matrix for

separating

nucleic acid components during DNA sequence analysis and during protein

identification. In the world at large polyacrylamide is used in water

purification to flocculate suspended organic matter, in irrigation

water to

improve soil texture and in pesticide formulations to limit spray

drift.

Recently the world health organization (WHO) had a closed meeting to

reveal the

finding that cooked vegetables had significant levels of acrylamide

(1). The

finding received worldwide notice because acrylamide is a potent nerve

toxin in

humans and effects male reproduction, causes birth defects, and cancer

in

animals. The WHO releases implied that the acrylamide finding was a

surprise and

that the pollutant probably arose from cooking the vegetables (1).

The WHO report failed to mention the extensive global use of

polyacrylamide

in pesticide formulations and in soil treatment and the predictable

residues of

the polymer in vegetables such as potato or in grain. The addition of

polyacrylamide to pesticide formulations is considered a trade secret

and rarely

reported while the soil treatment in irrigation water covers a million

or more

acres in the United States (US) and very large farmland areas

worldwide. Even

though the coverage of food crops with polyacrylamide formulations is

staggering

there seem to no available reports on polyacrylamide levels in food

crops. The

United States Department of Agriculture (USDA) serves a s both promoter

and

regulator of the use of polyacrylamide (PAM) in agriculture and that

agency does

not appear to have required thorough testing of the human and

environmental

consequences of polyacrylamide use..

Polyacrylamide is designated a non-toxic additive and that may

explain why

there has been little concern over its accumulation in food crops. Of

course

polyacrylamide may be contaminated with its toxic building block,

acrylamide,

and for that reason a limit of 500ppm acrylamide in polyacrylamide

preparations

has been arbitrarily determined to be acceptable for use in agriculture

or water

treatment. Furthermore, the polyacrylamide preparations (PAM) used in

irrigation

is most frequently a copolymer associated with acrylic (3) or other

polymer

plastic to provide stability, the polyacrylamide used in water

treatment is

often the co-polymer while the product used in pesticide formulations

is

protected as a trade secret but is likely to be a co-polymer.

It has been reported that PAM hydrogels degrade to release

acrylamide and

acrylate (4)[acrylate is a known teratogen] and corporate Material Data

Safety

Sheets sometimes indicate that acrylamide is a foreseeable degradation

product

of PAM and that acrylonitirile (a mutagen and carcinogen) and cyanide

are

thermal decomposition products of polyacrylamide super absorbent (5).

There are

studies showing that acrylamide is released from polyacrylamide after

exposure

to light and elevated temperature (6,7) while other studies concluded

that

acrylamide is not released from polyacrylamide during degradation

(8,9).

Glutarimide (a component of the drug thalidomide) a pharmacologically

active

compound was identified as a significant breakdown product of heated

polyacrylamide and the authors of that study stressed the need for

fuller study

of the breakdown products of polyacrylamide (9). There seems to be a

clear-cut

difference of opinion over the breakdown products of polyacrylamide.

The

authorities who maintain that acrylamide is not a breakdown product of

polyacrylamide stress that those who identify acrylamide as a breakdown

product

do not find the chemical as a large proportion of the breakdown

products of

polyacrylamide. That seems to be a specious argument, as if the thermal

degradation products dioxin or polyaromatic hydrocarbons are

inconsequential

because they are produced in relatively small amounts when they are

among the

most dangerous pollutants known. Moreover, the studies claiming to find

little

or no acrylamide in the breakdown products of polyacrylamide seem to

have

ignored the fact that the materials used commercially are most

frequently

co-polymers of acrylic acid or other polymers and the actual breakdowns

usually

take place on the surface of plant roots, leaves or stems or in the

soil matrix.

Certainly, polyacrylamide residue levels in food crops should have

been

studied as soon as polyacrylamide began to be used in pesticide

formulations and

irrigation water and such residues should be studied in the future.

Regulatory

agencies, such as, USDA and the Food and Agricultural Organization of

the United

Nations seems to be negligent in approving widespread employment of

polyacrylamide hydrogels and pesticide additives without having

undertaken

realistic analysis of the breakdown products and potential pollutants

consumed

by humans or released to the environment. It is rather discomforting to

learn

that foods we eat may be saturated with plastic polymer and their

unspecified

breakdown products and soon we may be saturated as well.

References

1.Weiss G. “Acrylamide in food:

Uncharted territory.” Science 2002, 297,27.

2. PAM Research Project USDA http://www.ars.usda.gov/is/AR/archive/jul02/form0702.htm

3.Hadar,H. and Keren,K. “Anionic

polyacrylamide polymers effect on rheological behavior of

sodium-montmorillonite suspensions” 2002 Soil Sci Soc Am J 66,19-25

4.Calker-,L. “The myth of

polyacrylamide hydrogels” http://www.cfr.washington.edu/research.mulch/myths/hydrogels.pdf

5.Castlre International Resources

“Material safety Data Sheet; Crosslinked polyacrylamide, superabsorbent

polyacrylamide and super absorbent polymer” 1999 by Dale Greenwood -

Castle International Resources Company. http://www.hydrosource.com/web_clp/990310/Msds0399.htm

6. E, Prues S and Ochme F.

Environmental degradation of polyacrylamides: Effect of artificial

environmental conditions. Ecotoxicology and Environmental Safety 1996,

35,121-35.

7. E, Prues S and Ochme F.

Environmental degradation of polyacrylamides: II Effects of outdoor

exposure. Ecotoxicology and Environmental Safety 1997, 37,76-91.

8.Leonard M. Ver Vers. Determination

of acrylamide monomer in polyacrylamide degradation studies by high

performance liquid chromatography. Journal of Chromatographic Science

1999, 37,486-94

9,Caufield,M,Qiao,G. and ,D.

“Some aspects of the properties and degradation of polyacrylamides”

2002 Chemical Reviews DOI: 10.1021/cr010439p