Backgrounder
Glyphosate and Biomonitoring Studies
Updated January, 2004
Monsanto Company
The term 鈥減esticide exposure鈥? may mean different things to different people. If someone had
been in a room or farm field when pesticides were being applied, the person might feel that he
or she had been exposed to pesticides. Indeed, many epidemiology studies seek to ascertain
people鈥檚 exposure to a pesticide by asking them if they have ever used or been present during
the use of the product.
In terms of determining potential risk, however, there is general agreement that exposure should
be based on the amount of pesticide that has penetrated into the body, the so-called internal
dose (Franklin et al., 1986; Chester and Hart 1986). Several studies indicate that glyphosate is
poorly absorbed by the body. When trace amounts are absorbed, through skin for example, the
body does not metabolize glyphosate. This means that glyphosate is not biologically
transformed into a different chemical or broken down into several different chemicals that may
have different toxicity profiles to glyphosate. Rather, it is eliminated unchanged, primarily in
urine (World Health Organization, 1994).
In addition to extensive laboratory research with animals to understand absorption through skin
and inhalation, a number of biomonitoring studies have been conducted to monitor the internal
exposure of people who mix, load, apply or otherwise come in contact with glyphosate.
Biomonitoring is the assessment of human exposure to chemicals by measuring chemicals or
their metabolites in human blood, urine or tissues. These biomonitoring studies have
demonstrated that normal and expected use of the product produces no or extremely low levels
of internal exposure.
The most extensive biomonitoring study is the Farm Family Exposure Study, conducted by
investigators at the University of Minnesota with guidance offered by an advisory committee of
recognized international experts in exposure assessment (Acquavella et al., 2004, Mandel et al.,
accepted for publication). The study monitored farm families, including spouses and children.
Urine samples were collected the day before glyphosate was to be applied, the day of
application and for three days after application. Sixty percent of the 48 farmers who applied
glyphosate had detectable levels of glyphosate in their urine on the day of application. The
detection method was capable of detecting 1 part per billion (ppb) glyphosate. The average
urine concentration was 3 ppb.
Two other biomonitoring studies were conducted for the U.S. Forest Service to determine the
internal exposure of people who work with or near glyphosate, including people who mix and
load and apply with backpack sprayers. One study, conducted in collaboration with the
University of Arkansas (Lavy et al., 1992), found that none of the urine samples collected from
the workers contained quantifiable levels of glyphosate (the limit of quantification was 10 ppb).
Although there likely was some dermal exposure, the lack of detectable levels in the urine was
attributed to the limited ability of glyphosate to penetrate the skin (Acquavella et al., 2001).
Backgrounder 鈥? Glyphosate and Biomonitoring Studies. 2004. Page 1 of 2
The other study involving herbicide workers was conducted in collaboration with Georgia Tech
Research Institute. That study, which is discussed by Acquavella et al. (2001) found that only 5
of 96 urine specimens contained quantifiable levels of glyphosate, the highest level being 14
ppb.
By learning the concentration in urine, it is possible to calculate the amount of glyphosate that
actually was absorbed by the body. In the three studies, the highest absorbed amount was
calculated to be about 97,000 times lower than a dose that caused no adverse effect when
administered to laboratory animals for several months.
These biomonitoring studies demonstrate that people who regularly work with glyphosate have
very low actual internal exposure. Biomonitoring studies differ from epidemiology studies, in
which groups of people 鈥? some with illnesses and some without 鈥? are asked to recall what
pesticides they may have used or come in contact with. Those studies depend on the ability of
the person to recall accurately, but more importantly, they do not measure whether there
actually was any internal exposure.
All the evidence from biomonitoring studies as well as animal laboratory studies demonstrates
that glyphosate use in real world conditions would not be expected to result in exposure capable
of causing serious illnesses.
References
Acquavella JF, Cowell JR, Cullen MR, Farmer DR, Pastides H. (2001) Implications of
Glyphosate Toxicology and Human Biomonitoring Data for Epidemiological Research. Journal
of Agromedicine 7(4): 7-27.
Acquavella JF, Alexander BH, Mandel JS, Gustin C, Baker B, Chapman P, Bleeke M. (2004)
Glyphosate Biomonitoring for Farmers and their Families: Results from the Farm Family
Exposure Study. Environmental Health Perspectives 112(3): 321-326.
doi:10.1289/ehp.6667. http://dx.doi.org/10.1289/ehp.6667
Chester G, Hart TB. (1986) Biological monitoring of a herbicide applied through backpack and
vehicle sprayers. Toxicology Letters 33:137-149.
Franklin CA, Muir NI, Moody RP. (1986) The use of biological monitoring in the estimation of
exposure during the application of pesticides. Toxicology Letters 33:127-136.
Lavy T, Cowell J, Steinmetz JR, Massey JH. (1992) Conifer seedling nursery exposure to
glyphosate. Archives of Environmental Contamination and Toxicology 22: 6-13.
Mandel JS, Alexander BH, Baker B, Honeycutt R, Chapman P, Acquavella JF. (accepted for
publication) Farm Family Exposure Study. Scandinavian Journal of Work & Environmental
Health.
World Health Organization. (1994) Glyphosate. Environmental Health Criteria No. 159. World
Health Organization, Geneva, Switzerland. Full text available on-line:
http://www.inchem.org/documents/ehc/ehc/ehc159.htm
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