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International Journal of Hygiene and Environmental Health 215 (2012) 570– 576

Contents lists available at SciVerse ScienceDirect

International Journal of Hygiene andEnvironmental Health

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stimating maternal and prenatal exposure to glyphosate in the communityetting

eather McQueen, Anna C. Callan ∗, Andrea L. Hinwoodentre for Ecosystem Management, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA 6027, Australia

r t i c l e i n f o

rticle history:eceived 8 August 2011eceived in revised form8 November 2011ccepted 4 December 2011

eywords:lyphosateaternal exposureietoncentrations

a b s t r a c t

Glyphosate is a herbicide in common use, in both agricultural and residential settings. Controlled residuestudies show that glyphosate persists in food crops, allowing for the potential of a large number of peopleto be exposed. Glyphosate is generally considered safe however there are a number of studies suggest-ing formulations or additives that may have adverse health effects. To assess the degree of exposureof pregnant women, this study measured glyphosate in composite food samples and estimated expo-sure based on food frequency questionnaire. 43 pregnant women were recruited and completed a selfadministered questionnaire with a food frequency component and provided a composite food sample.Twenty food samples were analysed with very low glyphosate concentrations (mean 0.08 mg/kg, range0.002–0.5 mg/kg) with residues detected in more than 75% of the samples. Maternal dietary exposurewas very low (0.001 mg/kg bw/day) and was considerably lower than the predicted National EstimatedDaily Intake of glyphosate (0.02 mg/kg bw/day). The estimated exposure based on measured glyphosate

in composite food samples corresponded to 0.4% of the acceptable daily intake for glyphosate, and thepredicted concentration from dietary information was 4% which is comparable to the National EstimatedDaily Intake of 5.5% of the Acceptable Daily Intake of glyphosate. Prenatal exposures were estimated tobe significantly lower. While residues of glyphosate are present in food, this study demonstrates thatexposure concentrations are low and confirms the current models used to estimate glyphosate exposure.

ntroduction

Glyphosate (N-phosphonomethyl glycine) is a herbicide thatontrols weeds or unwanted vegetation (U.S. Environmental Pro-ection Agency (U.S. EPA), n.d.). Glyphosate’s mode of action inlants is by inhibition of an enzyme in the shikimic acid path-ay called enolpyruvylshikimate-3-phosphate (EPSP) synthetase

Amrhein et al., 1980; Ecobichon, 2001; Franz et al., 1997). Whenpplied to plant foliage, glyphosate formulations are translocatedn a downward direction from the leaves (source of sugar synthe-is) to the sites of metabolic processes (sinks of sugar utilisation)uch as in the growing points at the tips of shoots and roots andn storage organs (meristematic tissue) (Duke and Powles, 2008;

cobichon, 2001; Franz et al., 1997). They are relatively nonselec-ive, hence they are toxic to most species of plant (Duke and Powles,008; Ecobichon, 2001; Franz et al., 1997).

Abbreviations: ADI, acceptable daily intake; FFQ, food frequency questionnaire;OD, limit of detection; MRL, maximum residue limits; U.S EPA, U.S Environmentalrotection Agency.∗ Corresponding author. Tel.: +61 8 6304 2349, fax: +61 8 6304 5509.

E-mail address: a.callan@ecu.edu.au (A.C. Callan).

438-4639/$ – see front matter © 2011 Elsevier GmbH. All rights reserved.oi:10.1016/j.ijheh.2011.12.002

© 2011 Elsevier GmbH. All rights reserved.

Glyphosate is used against a wide range of problem annual andperennial weeds and is widely used in crop production, generalland management and home gardens (Franz et al., 1997; U.S. EPA,1993; WHO, 1994). It is primarily released into the environmentduring mixing, application and cleanup when used as a herbicideand unintentional release from wind-drift and accidental spillagecan result in release to air, surface and groundwaters, soil and plants(WHO, 1994). Though glyphosate is the most heavily used herbicidein Australia, its use is not monitored (ATSE, 2002).

Controlled residue studies show that glyphosate persists in foodcrops, creating the potential for a large number of people to beexposed (FAO/WHO, 1986, 2006a; U.S. EPA, 1993). Regulatory stud-ies show that glyphosate per se is practically harmless to humans,wildlife and the environment; however, recent research indicatesother ingredients in the formulation increase the toxicity and avail-ability of glyphosate in mammalian (including human) cells, tissuesand organs, raising concerns about the safety of glyphosate (Axelradet al., 2003; Benachour and Séralini, 2009; Dallegrave et al., 2007;Hokanson et al., 2007; Richard et al., 2005).

Non-occupational exposures to glyphosate principally arisefrom consuming residues in food (Kamrin, 1997; U.S. EPA, 1993;WHO, 1994). In the home garden residents may be exposed toglyphosate from handling glyphosate products and also by contact

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ith glyphosate after application (U.S. EPA, 1997). Exposure esti-ates are calculated based on the amount of agent that could enter

he human body by ingestion, inhalation or skin contact, whereasn absorbed dose is the amount of agent that is absorbed across theastrointestinal tract, lungs or skin (U.S. EPA, 1992). An exposurestimate is calculated from the concentration of the agent in theedium multiplied by the rate of intake (inhalation and ingestion)

r uptake (dermal absorption) and divided by body weight (U.S.PA, 1992). For an absorbed dose, bioavailability data of the chem-cal across the gastrointestinal tract, lungs or skin and the placentafor foetal exposure) are included in the calculation of exposureU.S. EPA, 1992). Exposure estimates are then put in the contextf the health standard or guideline for that agent and a qualitativevaluation of the potential health risks to exposed populations isade, in light of the assumptions and uncertainties of the exposure

ssessment methodologies (Berglund et al., 2001; EnHealth, 2002;ieuwenhuijsen, 2003; OECD, 1999; U.S. EPA, 1992). Validatedethods for assessing the diets of pregnant women as a means of

stimating prenatal exposure are scarce (Potischman et al., 2006).The youngest age group in the 20th Australian Total Diet Survey

s nine months (FSANZ, 2003), which does not take into account thevidence that prenatal children are the most vulnerable subgroupBarker, 1992). The Acceptable Daily Intake (ADI) for glyphosateoes not recognise the toxic potential of some of the adjuvants

n glyphosate formulations (Cox and Surgan, 2006) and an ADI issually set for a 60 kg adult, which may not adequately recognisehe biological vulnerability of prenatal children to environmentalxposures (ATSE, 2002; Pennycook et al., 2004).

There is, therefore, a need for research to assess the potential forxposure to glyphosate among pregnant women and to estimatehe risks of prenatal exposure to such a widely used product.

The aim of this study was to assess maternal exposure as a surro-ate for prenatal exposure. To achieve this aim, the study collectedood intake and gardening activities of a group of pregnant womennd measured the concentrations of glyphosate in both table-readyood. The study aimed to compare the measured maternal dietaryxposure estimate to glyphosate with predicted Australian andnternational dietary glyphosate exposure estimates.

aterials and methods

The study was a descriptive cross-sectional study of glyphosatexposure via diet in non-occupationally exposed urban- dwellingregnant women. Ethics approval was granted by Edith Cowan Uni-ersity’s Human Research Ethics Committee (Reference# 06-45).ll participants provided written informed consent prior to dataollection.

tudy area

The Perth Metropolitan Region was chosen as the study areao avoid confounding factors that might be introduced from theural setting, particularly where agricultural spray drift of herbi-ides may be an issue.

tudy population

The study recruited pregnant women from across the Perthetropolitan Region. The selection criteria were pregnant women

ged over 18 years, eating conventionally grown food, and with noeported occupational exposure to glyphosate in the household.

ecruitment

Forty three pregnant women were recruited through presen-ations at the antenatal clinics of several hospitals in the Perth

nd Environmental Health 215 (2012) 570– 576 571

metropolitan area and by ad hoc methods that included advertisingin the community and through the local media and word of mouth.Thirteen women took part in the study during winter samplingin July/August 2006 and 30 during spring sampling in November2006. Four participants took part in the study during both samplingperiods.

Data collection

Each participant was asked to complete a self administeredquestionnaire that included a food frequency component, and toprovide a composite sample of table ready food.

Self administered questionnaire

A self-administered questionnaire was developed to collectinformation on participants’ demographic characteristics, theirdietary intake and gardening activities in order to estimateexposure to glyphosate based herbicides. The questionnaire alsoincluded a semi-quantitative food frequency questionnaire (FFQ).The FFQ used was a modified form of The Cancer Council VictoriaDietary Questionnaire for Epidemiological Studies Version 2 (Giles& Ireland, 1996).

Composite table ready food samples

Participants were asked to provide a composite food sample bycollecting a small serve (approximately one dessertspoon) of everyfood item they consumed during one twenty four hour period.Participants were asked to prepare food to table ready state asusual and place a sample of each food item in a labelled freezerbag/container at each eating occasion. Participants were asked tofreeze their food samples in a domestic freezer as soon as possi-ble after collection. Samples were collected by the research teamand stored at −20 ◦C until analysis. As food was anticipated to bethe major contributor to dietary intake, beverage samples wereexcluded from this study. All food samples were weighed andindividual samples from each participant combined to create onecomposite sample per participant.

Food samples were shipped frozen to Agrisearch Analytical(NSW, Australia) for chemical analysis. Due to budgetary con-straints, 20 food samples were analysed for glyphosate. Sampleswere randomly selected for analysis from the two sampling periodsusing Random Number Generator Pro (accessed June 2006 from:http://www.segobit.com/rng.htm).

Chemical analysis of food samples

Food samples were analysed for residues of glyphosate andaminomethylphosphonic acid (AMPA), the principle degradationproduct of glyphosate, by electrospray ionisation–liquid chro-matography tandem mass spectrometry at a laboratory that wasISO/IED 17025:2005 National Association of Testing Authoritiesaccredited to test for glyphosate residues in food commoditiesby this method. The reported glyphosate concentrations wereexpressed as the sum of glyphosate and AMPA as per the AustralianPesticides & Veterinary Medicines Authority (APVMA) residue def-inition (APVMA, 2008b). The limit of quantitation was 0.01 mg/kgand the limit of detection (LOD) was 0.005 mg/kg for this methodof determining glyphosate in assorted food products.

Data management and analysis

The food frequency questionnaire (FFQ) section of the question-naire was analysed by The Cancer Council Victoria. The remaining

5 iene and Environmental Health 215 (2012) 570– 576

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Table 1Participant reported socio-demographic characteristics of all participants and thesubset having glyphosate measurements in food.

Number of participants Total studypopulation(n = 43)

Subset withcomposite foodanalysis (n = 20)

Age (years)Mean 32.1 32Median 32.1 33.5Range 22–41 22–41

Highest level of education (%)Tertiary 72.1 75Year 12/TAFE equivalent 18.6 15Year 10 7.0 10Did not complete high school 2.3 0

Current or last occupationa (%)Managers 7.0 15.0Professionals 53.5 45Technicians and trades workers 2.3 0Community/personal service 4.7 5Clerical and administrative 23.3 25Sales workers 2.3 10

Duration Lived at current address (years)Mean ± SD 2.8 2.8Range 0.1–8.9 0.1–8.9Median 2.7 2.7

the mean solid food intake reported in this study is very simi-lar to average mean daily intake (1084 g) and range 564–2447 g(5th–99th percentile) determined by dietary studies conducted onadults in 16 countries across Europe (EFSA, 2008). The combined

Table 2Participant reported body weight and derived gestational age of foetus.

Number of participants Total studypopulation(n = 43)

Subset withcomposite foodanalysis (n = 20)

Maternal pregnant body weight (kg)Mean ± SD 71.1 72.3Range 51–121 51–121Median 67 65.8

Gestational Age of foetusa at sampling (weeks)

72 H. McQueen et al. / International Journal of Hyg

uestionnaire data was analysed using SPSS v14.0 (student ver-ion). Descriptive analysis of the entire study population wasompared with the subset of 20 participants whose composite foodample had been analysed for glyphosate. There were no significantifferences between the subset and the entire study population.

The general equation for calculating the average daily potentialxposure for the ingestion of chemical residues was given by thequation:

xposure (mg/kg bw/day) = Food consumption (kg/day)

× concentration of residue in food (mg/kg) body

weight (kg) (U.S. EPA, 1992)

For dietary intake, where food was consumed intermittentlyhroughout the day, the average intake rate of the medium multi-lied by the sum of the exposure durations for all events divided byhe time period over which the exposure is averaged (IR × ED/AT)ecomes the total amount of food consumed per day (U.S. EPA,992). Thus, the equation used by FSANZ (2003) for chronic dietaryxposure to pesticides estimates average daily potential exposuren milligrams of chemical residue per kilogram of body weight peray for each individual and is given by:

Estimate of Maternal Dietary Intake Equation (U.S. EPA, 1992)

DDpot = [C × IR × ED][BW × AT]

here, ADDpot, average daily potential exposure; C, average con-entration of the chemical in the medium (chemical specific:.08 mg/kg); IR × ED, average intake rate of the medium x the sumf the exposure durations for all events (site specific: 1083 g/day);W, body weight (kg) (site specific: 72 kg); AT, time period overhich the exposure is averaged (converted to days) (site specific:er day).

esults

ocio-demographic characteristics

The study population comprised 43 individuals with a mean agef 32 years (Table 1). Twenty participants had their food samplesnalysed for glyphosate and their characteristics are also noted inable 1. The study population was well educated with the majorityaving completed tertiary education (Table 1). On average, partic-

pants had resided at their current address for almost three yearsTable 1).

The median self-reported pregnancy body weight at the timef sampling was 67 kg, with the maximum body weight reporteds 121 kg (Table 2). The subset of pregnant women were slightlyeavier but the difference was not significant (Table 2).

ietary consumption

Seventy-seven per cent of women reported eating ‘no specialype of diet’ (data not shown). The types and amounts of food con-umed by participants as well as the range of maximum residueimits of glyphosate for foods in selected major food groups is sum-

arised in Table 3.The study population ate a diverse diet, comprising of foods from

ll the major food groups as well as those from a wide range of sub-ajor food groups. At least 80% of participants reported eating from

ll major food groups (data not shown).The food groups cereals, legumes and pulse products and fats

nd oil products represent the greatest potential for glyphosatexposure, due to high maximum residue limits (MRLs) for

a Occupations coded to 2006 Australian and New Zealand Standard Classificationof Occupations (ANZSCO, 2006).

glyphosate associated with pre-harvest treatment during crop pro-duction (Table 3). The MRLs of glyphosate are highest for cerealsand cereal products and cereal-based products/dishes, particularlythose that contain wheat and wheat bran, for which the MRLs are 5and 20 mg/kg respectively. High MRLs, ranging from 5 to 10 mg/kg,also apply to mature legumes and pulses. While MRLs are unlikelyto reflect actual dietary intake, they nominate the foods in whichresidues of glyphosate are permitted and the variability of MRLsamong food types indicates that consumers are exposed to differentlevels of glyphosate from eating different foods (Table 3).

The amount of food consumed by the study population fromselected food groups and the percentage these food groups con-tribute to the total diet are summarised in Table 4. The mean foodconsumption was derived from the 74-item FFQ and represents anestimate of the amount of these foods and beverages consumed perday on average by study participants (Table 4).

The mean daily food intake of the study population was1066 g/day and ranged from 525 to 2436 g/day (Table 4). The widerange of reported food intakes might indicate a degree of over- orunder- reporting of food consumption by participants. However,

Mean ± SD 26.8 25.3Range 9–38 9–36

a Gestational age of foetus calculated as 40 weeks minus the number of weeksbetween the sampling date and self-reported date of confinement.

H. McQueen et al. / International Journal of Hygiene and Environmental Health 215 (2012) 570– 576 573

Table 3The range of maximum residue limits (MRL) of glyphosate for each food group.

Selected food groups MRLa [range of MRLs for food itemsin food group] mg/kg

Cereals and cereal products [Tb0.1–20]Cereal-based products anddishes

[Tb0.1–20]

Fruit products and dishes Most fruits [b0.05–0.5]Vegetable products anddishes

Most vegetables [b0.01–b0.1]

Legume and pulse productsand dishes

Most mature legumes/pulses [5–10]

Milk products and dishes Milks [b0.1]; soya beans (dry) [10]Meat, poultry and gameproducts and dishes

Most meats [b0.1]

Fish and seafood productsand dishes

No MRLs

Egg products and dishes Eggs [b0.05]Sugar products and dishes [T0.3, T5]Seed and nut products anddishes

Tree nuts and oilseeds [b0.05–0.2]

Fats and oils [Tb0.1, b0.1]

MRL, maximum residue limit. ‘T’, temporary use of the MRL or residue definitionpending experimental work or during phase out of the MRL (APVMA, 2008a).

a Maximum residue limits apply either to individual foods or a food group, inwhich case the MRL applies to all members of the food group listed in the CodexClassification of Foods and Animal Feeds (FAO/WHO, 1993). Residues are also accept-able in processed foods that consist of, contain or are manufactured from primaryfood commodities for which MRLs have been set (e.g. fruit juices) provided thatresidues are lower than the respective MRLs of the raw ingredients (APVMA, 2008a).M

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Table 6Estimated maternal exposure to glyphosate (n = 20).

Estimated dietaryintake (mg/day)

Estimated dietary exposure(mg/kg bw/day)

% ADI

Mean 0.07 0.001 0.4Median 0.06 9 × 10−4 0.3Range 2 × 10−5 to 5 × 10−3 0.005–2

Estimated dietary intake, mean analytical results for concentrations of glyphosatein food multiplied by mean food consumption. Estimated dietary exposure, mean

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aximum residue limits shown are current at October 2008 (APVMA, 2008b).b MRL is set ‘at or about’ the analytical limit of quantitation and residues shouldot be detected.

ereals and cereal-based products food groups contributed a meanf 333 g to the participants’ daily food intake (Table 4).

oncentrations of glyphosate in food

Quantifiable residues of glyphosate were found in 75% of theomposite food samples tested with a mean of 0.08 mg/kg and

able 4mount of food consumed by major food groups (n = 43).

Selected food groups Mean (g/day)

Cereals and cereal products 255.4

Cereal based products and dishes 78.0

Fruit products and dishes 253.3

Vegetable products and dishes 166.3

Legume and pulse products, dishes 11.1

Total milk and milk products 103.1

Meat, poultry products and dishes 90.3

Fish and seafood product and dishes 27.8

Egg products and dishes 20.3

Snack foods 5.1

Sugar products and dishes 13.7

Confectionary 14.4

Seed and nut products and dishes 8.1

Fats and oils 15.3

Miscellaneous 4.2

Total food consumed 1066.4

able 5oncentration of glyphosate residuea concentrations determined in composite food samp

By season Number of samples Mean ± SD (mg/kg)

Winter samples 5 0.03 ± 0.3

Spring samples 15 0.09 ± 0.1

All samples 20 0.08 ± 0.1

OD = 0.005 mg/kg. Where glyphosate residue concentrations are <LOD, LOD/2 has been ua Glyphosate is expressed as the sum of glyphosate and aminomethylphosphonic as per

APVMA, 2008b).

analytical results for concentrations of glyphosate in food multiplied by mean foodconsumption divided by mean maternal pregnancy body weight (U.S. EPA, 1992).

range of <0.005–0.5 mg/kg (Table 5). The wide range of concen-trations reported is due to one high value (0.5 mg/kg) and 2 valuesbelow the LOD. Wide-ranging concentrations of glyphosate are typ-ically reported in supervised trials (FAO/WHO, 1986, 2006a).

Estimated maternal exposure to glyphosate

The mean estimated maternal daily dietary exposure toglyphosate residue was calculated from the concentrations mea-sured in composite food samples by the subset of twentyparticipants. The concentration calculated was 0.001 mg/kg bw/daywith a range of 2 × 10−5 to 0.005 mg/kg bw/day (Table 6). The guide-line value for the intake of pesticides via the oral route is the ADIwhich for glyphosate in food has been set at 0.3 mg/kg bw (DoHA,2007). When the mean estimated maternal daily dietary exposureto glyphosate residues is expressed as a percentage of the ADI ofglyphosate, estimated maternal exposure accounts for 0.4% of theADI with a range of 0.005–2%. Thus, all estimated exposures wereless than or equal to 2% of the ADI of glyphosate and well below theapplicable health guideline.

It is expected that foetal exposures would be significantly lower

due to the small percentage of glyphosate predicted to cross theplacenta (15%) based on an in vitro placental perfusion study (Moseet al., 2008).

Median (g/day) Range (g/day) % of diet

184.6 43.3–1386.2 23.962.4 15.3–252.5 7.3

249.9 55.5–489.2 23.8147.2 27.6–392.0 15.6

6.7 0–47.3 1.0111.8 0–291.6 9.7

78.2 0–244 8.522.0 0–108.1 2.612.9 0–60.0 1.9

2.8 0–41.8 0.515.2 0–34.0 1.310.4 0.5–70.7 1.4

5.1 0–44.0 0.814.0 0–42.0 1.4

2.6 0–20.6 0.41011.9 524.6–2436.2 100

les.

Minimum (mg/kg) Maximum (mg/kg) % samples <LOD

<0.005 0.07 400.005 0.5 –<0.005 0.5 10

sed to calculate mean concentrations (U.S. EPA, 1992). Australian Pesticides & Veterinary Medicines Authority (APVMA) residue definition

574 H. McQueen et al. / International Journal of Hygiene a

Table 7Predicted theoretical maximum daily intakea of glyphosate for study population.

n = 20 Predicted dietaryintake of glyphosate(mg/day)

Predicted dietaryexposure to glyphosate(mg/kg bw/day)

% ADI

Mean ± SD 0.7 0.01Range 0.3–3 0.004–0.05 1–17Median 0.5 0.008 3

a Theoretical maximum daily intake = �MRLi × Fi, where MRLi is the maximumresidue level for a given food commodity and Fi is the daily consumption value ofthat food commodity per person (WHO, 1997). Where MRLs vary among ingredientsin mixed foods, AUSNUT recipes have been consulted to determine the percentageda

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ifferent ingredients contribute to a mixed food and proportional MRLs have beenpplied in calculations (FSANZ, 2009; FSANZ, n.d.-a, n.d.-b).

Dietary intake of glyphosate was also predicted based on MRLsTable 3) allocated for food groups and estimated consumptionTable 4). The results of the prediction of concentrations and thosestimates based on measurements of intake and exposure to dietarylyphosate are shown in Table 7. These calculations show thathe mean predicted estimate of glyphosate intake from the dietas 0.7 mg/day, with a predicted exposure estimate of 0.01 mg/kg

w/day (Table 7). When compared with the Acceptable Daily Intakeor glyphosate, the predicted maternal dietary exposure estimateccounted for 4% of ADI for glyphosate. The predicted dietary intakef glyphosate is a factor of ten higher than the measured dietaryxposure estimate (Tables 6 and 7).

iscussion

This study has shown that a high percentage of composite foodamples contained low concentrations of glyphosate with a meanoncentration of 0.08 mg/kg and a wide range. Comparison of thisesult with other studies that have directly measured the levelsf glyphosate in food is limited due to a paucity of food surveil-ance or total diet studies that feature glyphosate. Granby and Vahl2001) provide a published source of residue data, which focussedn small grain cereals (wheat, rye, oat and barley) since they rep-esent the foods most likely to contribute the highest residuesf glyphosate to the diet (FAO/WHO, 1986; Granby and Vahl,001; WHO, 1994). They found glyphosate resides in approximately0% of samples (LOD 0.01 mg/kg) with an average concentrationcross all cereals of 0.08 mg/kg in 1998 and 0.11 mg/kg in 1999Granby and Vahl, 2001). These results are in agreement withhe current study in terms of both the proportion of samples inhich glyphosate was detected and the concentrations determined

Granby and Vahl, 2001). Wide-ranging residue concentrationsere also reported in all supervised trials and hence variability may

e the norm rather than the exception (FAO/WHO, 1986, 1988a,006a).

Most of the available data, however, are from supervised croprials, many of which are many years old, which formed the basis ofstimating the maximum residue limits of glyphosate in food andnimal feed (FAO/WHO, 1986, 1988a, 1995, 1998, 2006a; U.S. EPA,993).

The results of the most recent supervised trials showed that con-entrations of glyphosate in food crops ranged from undetectablen bananas (i.e., less than the typical detection limit of 0.05 mg/kg)o 20 mg/kg in barley and soya beans (FAO/WHO, 2006b). In wheatrain, concentrations of glyphosate at harvest ranged from 0.1 to.5 mg/kg (median value 1.2 mg/kg) (FAO/WHO, 2006a). A wideange of residue concentrations was observed for all crops, due to

combination of factors including the different responses of plantpecies to glyphosate treatment and the use pattern of glyphosateith respect to the frequency and timing of sprays as well theethod of application (FAO/WHO, 2006a). The U.S. EPA reported

nd Environmental Health 215 (2012) 570– 576

glyphosate residues in crops at concentrations of <0.05–0.15 mg/kg(U.S. EPA, 1993), which is lower than found in this study.

The proportion of samples in which glyphosate was detected inthe current study was closer to that reported in pre-harvest trials;the concentrations, however, were considerably lower (FAO/WHO,2006b). A feasible explanation for lower residue concentrations isthe analysis of glyphosate in ‘table-ready’ food as opposed to atharvest. A reduction in glyphosate concentrations is expected postharvest due to storage and transport to the point of sale and also as aresult of industrial and consumer food preparation practices such aswashing, peeling and cooking or otherwise processing foods priorto canning, drying or freezing (FAO/WHO, 1988a, 1988b; U.S. EPA,2000).

The presence of glyphosate in a high percentage of food sam-ples, albeit at low concentrations, suggests that glyphosate persistsin the food chain ‘beyond the farm gate’, throughout the commer-cial and consumer practices involved in food storage, transport,processing, preparation and cooking to the point of consumption.This result accords with processing studies on milled and processedcereal grains, which showed the presence of glyphosate in bread,beer and groats (minimally processed oats) with concentrationsranging from <0.05 to 4.7 mg/kg, <0.05 to 2.9 mg/kg and 0.27 to5.3 mg/kg, respectively (FAO/WHO, 1987).

Cereal foods are considered the most important source ofdietary glyphosate due to pre-harvest applications (FAO/WHO,1986, 1988a, 2006a; Granby and Vahl, 2001). For the women inthe present study, cereal foods were also important in terms ofglyphosate exposure comprising on average 31% of the total dailydietary food intake, with all participants consuming them.

This study estimated that the mean dietary exposure of a smallgroup of urban-dwelling pregnant women to glyphosate comprised0.4% of the ADI for glyphosate. This exposure estimate is a factorof ten higher than Granby and Vahl’s (2001) estimated glyphosateintake of 0.04% of the ADI. However, the Granby and Vahl (2001)study had a lower estimate of average daily consumption of cerealfoods, and the study was restricted to only this food group.

The large range of dietary exposure observed in the presentstudy is likely due to a combination of factors including a widerange of residue concentrations in food and wide-ranging inter-individual variations in the amounts of food consumed, participantbody weights, stage in pregnancy, and particularly the small samplesize.

The predicted exposure of this study’s population from dietbased on MRLs was calculated as 0.01 mg/kg bw/day, 4% of theADI for glyphosate, ten times higher than the measured expo-sure estimate. When the predicted estimate of dietary exposurein the present study is compared with predicted exposure esti-mates of national and international regulatory authorities, thepredicted exposure estimate was lower than, but comparable with,the National Estimated Daily Intake validated by Food StandardsAustralia New Zealand (FSANZ) in 2006 of 0.016 mg/kg bw/day,representing 5.5% of the ADI of glyphosate. This study’s predictedexposure estimate is also in fair agreement with the internationalTheoretical Maximum Residue Contribution of 0.025 mg/kg bw/dayin the overall U.S. population (U.S. EPA, 1993), but considerablyless than a European study, which found that the TheoreticalMaximum Daily Intake (excluding water and products of ani-mal origin) for a 60 kg adult was 15% of the ADI of glyphosate,based on the FAO/WHO European Diet (European Commission,2002).

A lower predicted exposure estimate for the present study thanFSANZ’s prediction for glyphosate is expected due to different

methodological factors, how food consumption data were collectedand the use of individual diet records as opposed to national dietsheets. Other possible explanations relate to differences in calcu-lating the MRLs of glyphosate in mixed foods.

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Predicted exposure estimates are expected to be higher thaneasured exposure assessments because predicted exposure esti-ates intentionally project a ‘worst case’ scenario of the risk,hich is health protective (APVMA, 2008c). However, the extent

f agreement between predicted studies depends on the level ofefinement that has been achieved in predicting both residue datand dietary intake, which in turn is dependent upon the avail-bility of supporting data (Harris and Gaston, 2004; WHO, 1997).sing progressively refined methodologies to predict the chronicietary intake of glyphosate from the consumption of cereal prod-cts, Harris and Gaston (2004) in the United Kingdom calculated

ntakes from 11% declining to 0.6% of the ADI of glyphosate due tohe progressively refined methodologies including precise infor-

ation concerning residues in food. These have been derived fromn-country field residue trials (WHO, 1997) and food consump-ion derived from national food surveys (WHO, 1997). The mostefined predicted dietary intake reported of 0.6% of the ADI oflyphosate (Harris and Gaston, 2004) is in good agreement withhe measured dietary intake of glyphosate estimated in the presenttudy of 0.4% and suggests that the range of data now avail-ble for predicting exposure to dietary glyphosate may be closeo actual. For pesticides like glyphosate, where toxicity is lownd analysis expensive, it is encouraging that predictive modelsf exposure seem to be consistent with measured estimates ofxposure that have been determined by indirect methods of dataollection.

Foetal exposure from glyphosate residues in maternal diet wasxpected to be considerably lower than maternal exposure. Thiss due to the physicochemical properties of glyphosate: as a polar,

ater-soluble compound it is poorly absorbed across both the gas-rointestinal tract (30–36%) (Ridley and Mirly, 1988; WHO, 1994)nd the placenta (15%) (Mose et al., 2008). Ignoring further lossesf glyphosate due to distribution in the blood and tissues prior toelivery at the placenta, then mean foetal exposure from maternalietary exposure was estimated to be minimal.

onclusion

This study has confirmed the presence of residues of glyphosaten table-ready food. The estimated exposure of the pregnant

omen in this study to dietary glyphosate using measured con-entrations in food represented a very small percentage of the ADIor glyphosate and that measured dietary intake of glyphosate inhis group of women is approximately one order of magnitudeower than the nationally predicted dietary intake of glyphosate.his indicates the extent of conservatism inherent in the method-logy for predicting the intake of residues of glyphosate fromood. This study also found that the measured dietary intakef glyphosate in this group of women compared well withhe most refined predicted exposure estimates available, sup-orting the current models for predicting dietary exposure tolyphosate.

It is suggested that a larger study be conducted to ascertainxposure to the formulation ingredients of glyphosate, as opposedo glyphosate alone, to confirm the low exposures in this study butmportantly to assess the risks associated with formulation ingre-ients. It is also suggested this be combined with assessments of

ndividual food items instead of composite food samples.

cknowledgments

The authors would like to thank the Centre for Ecosystemanagement, Edith Cowan University for funding this study. The

unding body had no input into the design or implementation ofhe project.

nd Environmental Health 215 (2012) 570– 576 575

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