Trends in glyphosate herbicide use in the United States and globally

Use data

Throughout this paper, all references to glyphosate or glyphosate-based herbicides encompass all commercial end-use formulations. All data on volumes of glyphosate applied refer to kilograms or pounds of the active ingredient glyphosate, rather than glyphosate plus the adjuvants and surfactants included in an end-use formulation to enhance uptake by weeds and facilitate mixing and spray applications.

Glyphosate is applied in a variety of forms including isopropylamine salt, ammonium salt, diammonium salt, dimethylammonium salt, and potassium salt [1]. E.g., in its corn pesticide use survey in 2014, the National Agricultural Statistics Service (NASS) collected data on four different forms of glyphosate applied at different rates: isopropylamine salt, glyphosate, glyphosate ammonium salt, and glyphosate potassium salt [11]. Total corn hectares treated with glyphosate in the U.S. and kilograms of active ingredient applied are the sum across the four forms of glyphosate. “Total glyphosate” rate of application is calculated as an average of the four application rates reported for the different forms of glyphosate, weighed by the area treated with each form of glyphosate. The same process can be used to calculate “total glyphosate” average number of applications per hectare.

U.S. data sources

The U.S. Department of Agriculture (USDA), through the National Agricultural Statistics Service (NASS), has collected reasonably comprehensive pesticide use data for major grain, row crop, fruit, and vegetable crops since 1990 [18]. Periodic USDA surveys are also available to track pesticide use on major crops back into the 1970s.

Between 1997 and 2007, the U.S. Environmental Protection Agency (EPA) issued several reports on the volumes of pesticides applied in the agricultural, industrial/government, and urban/suburban sectors [19, 20, 21, 22, 23]. EPA use reports capture a number of lower-volume pesticide uses not included in USDA surveys and are the only public source of data on industrial/government and suburban/urban pesticide use.

Data on glyphosate use on specific crops in the U.S. are primarily drawn from pesticide use surveys carried out by the USDA’s NASS. Pesticide applications at the national and state level have been reported since 1990 by NASS for most major field crops; fruit crops have been surveyed in odd years; and vegetables have been covered in even years [18].

Estimates of overall GBH use by U.S. farmers and ranchers are available from three sources: the sum of crop-specific NASS data in any given year; the EPA periodic reports noted above; and, the pesticide use data set compiled by the U.S. Geological Survey (USGS), which in turn draws heavily on private survey data [24, 25, 26]. Both the EPA and USGS use data compilations augment NASS data with a variety of other information sources that cover uses not included in NASS surveys. In addition, a number of private companies conduct surveys of pesticide use in the U.S. and around the world, although detailed results are not publicly accessible.

NASS surveys a limited number of crops in any given year. In the tables that follow, pesticide use is linearly interpolated in years lacking survey data but bounded by reported values. In years before the first, or after the last NASS survey, annual values are extrapolated (see [27], Additional file 1: Tables for details).

In each year, NASS strives to collect data on states that collectively account for at least 85 % of the area planted nationally to a given crop. For some crops, 15 or more states are surveyed to reach this threshold, while in other crops only two states are required (e.g., lemons in 2011, two states; corn in 2010, 21 states). Accordingly, when NASS reports national estimates of total pesticide use on surveyed acres of a given crop, the data typically underestimate total national crop use by ~15 %, since national acres planted always exceeds NASS acres surveyed. This is why in several Additional file 1: Tables [27] the pounds of herbicides applied are reported on both NASS-surveyed acres and total national acre. To estimate use on all planted hectares/acres, the average rate of application per crop year on NASS-surveyed acres is applied to the total planted area [28].

Total volume of glyphosate applied

NASS use data were downloaded and integrated into the “Pesticide Use Data System” (PUDS). Additional file 1: Tables S6–S15 [27] report glyphosate use in the U.S. on grain crops, fruits, vegetables, nuts, and other crops for 1982, 1992, 1995, 1998, 2001, 2004, and every 2 years thereafter through 2014. These tables report average rates of glyphosate application and rate per crop year weighted by the acres treated with each of the multiple forms of glyphosate included in NASS surveys. Total pounds of all forms of glyphosate applied to all crops surveyed by NASS are shown in Additional file 1: Table S17 [27]. Values in years when NASS did not survey a given crop are interpolated or extrapolated (see Additional file 1: Table S17 for details).

Little or no government or published survey data are accessible on the volume of glyphosate applied on canola and pima cotton, as well as two more recently approved and planted GE-HT crops (alfalfa, sugar beets). Estimates of GBH use on these crops were made for 2012–2014 in Additional file 1: Table S16, based on NASS data on acres planted, estimates of adoption of glyphosate-tolerant varieties issued by commodity groups, academic weed management specialists, or in trade press articles.

EPA pesticide use summary reports

Pesticide use reports have been released by the EPA for 1987, 1993, and every two years thereafter through 2007 [19, 20, 21, 22, 23].

These reports encompass more crops and agricultural uses than the NASS reports, and also quantify use in three sectors: “U.S. Agriculture,” “Industrial/Commercial/Government,” and “Home and Garden.” EPA pesticide use reports draw on NASS survey results, a number of proprietary pesticide use datasets, and pesticide production and use data submitted by registrants, or collected during the course of a regulatory review of a given pesticide.

The EPA has not reported pesticide use data since 2007. However, NASS coverage of the major uses of glyphosate is somewhat consistent since 2007, and the U.S. Geological Survey (USGS) has also issued detailed reports and a dataset of pesticide use covering 1992-2011 [25, 29]. Results from NASS, EPA, and USGS are integrated in Additional file 1: Table S18 [27] to produce annual data from 1974 through 2014 in glyphosate use in agriculture, non-agricultural applications, and total glyphosate use.

Global glyphosate use data sources and estimates. A special issue of the journal Pest Management Science in 2000 focused on glyphosate uses, issues, and challenges. Woodburn [29] summarized global glyphosate use from 1994–1997, and provided valuable information on agricultural and non-agricultural uses. Woodburn’s analysis drew upon proprietary data sources and surveys.

Several sources of industry data on global glyphosate production are available for 2011–2014 [30, 31, 32, 33]. Global use data in Additional file 1: Table S23 between 1997 and 2011 are interpolated and track the annual rates of growth in the U.S.

Glyphosate use on herbicide-tolerant hectares

Global soybean production in 2014 was 315.4 million metric tons (11.6 million bushels), with the U.S. (108 million metric tons), Brazil (94.5 mill. metric tons), and Argentina (56 mill. metric tons) accounting for 82 % of the global harvest [34]. The International Service for the Acquisition of Agri-Biotech Applications (ISAAA) compiles annual, global data by country, continent, and worldwide on hectares planted to various GE crop varieties ([14, 15, 16, 17], [27], Additional file 1: Table S20). Data from these briefs were combined with estimates of average glyphosate rates of application ([27], Additional file 1: Table S21), yielding estimates of total glyphosate use from 1996 to 2014 on GE, herbicide-tolerant cotton, maize, soybeans, and canola, and globally for all crops ([27], Additional file 1: Table S23).

Use in Argentina and Brazil. GE-HT soybeans accounted for 100 and 93 % of the soybean hectares planted in Argentina and Brazil in 2014 [34]. Sistema Integrado de Información Agropecuaria (Ministerio de Agricultura Ganadaria y Pesca) reports data on hectares planted to soybeans in Argentina [35], and the Instituto Brasileiro de Geografia e Estatística (IBGE) provides the same data for Brazil [36]. For Argentina and Brazil, Soystats [34] provides percent of area planted to GE-HT soybeans for 2000–2014. Benbrook [37] and Meyer and Cederberg [38] provide information on glyphosate use rates per crop year, which are substantially higher than those in the U.S. Ferraro and Ghersa [39] also document applications to soybeans in Argentina that can range up to seven per year, substantially more than in the U.S.

Glyphosate use in the U.S

The 12.5 million kg applied in 1995, prior to the GE era, made glyphosate the seventh most heavily applied pesticide in U.S. agriculture that year, according to the EPA ([27], Additional file 1: Table S19). The top-six pesticides applied by U.S. farmers and ranchers in 1995 included two herbicides mostly used on corn (#1 atrazine, and #2 metolachlor), three soil fumigants primarily applied on fruit and vegetable crops (#3-5, metam-sodium, methyl-bromide, dichloropropene), and one broad-leaf herbicide relied on in multiple cropping systems (#6, 2,4-D).

As GE-HT crops gained market share in 1996–2000, agricultural applications of glyphosate in the U.S. rose rapidly, reaching 36 million kg (79 million pounds) by 2000 (Table 1). That year, agricultural uses of glyphosate accounted for 80 % of total national use (in 1974, the agricultural share of total glyphosate use was about 60 %). A decade later in 2010, agriculture’s share had risen to 90 %. From 1974–2014, a total of 1.37 billion kg of glyphosate (3.0 billion pounds) was applied in the U.S. agricultural sector (Table 1).

Glyphosate use in the agricultural sector rose 300-fold from 1974 to 2014 (0.36–113.4 million kg; 0.8–250 million pounds). Non-agricultural uses rose less dramatically, by 43-fold in the same time period, because there were far fewer new, non-agricultural uses registered.

Use by crop in the U.S

Detailed glyphosate use data for NASS-surveyed crops are provided in Additional file 1: Tables S11–21 [27] for 1982, 1992, 1995, 1998, 2001, 2004, and every even year thereafter through 2014. In each table, the following crop groups are used: grains, fruits, vegetables, nuts, and other crops. For each crop and year, the data points include percent of acres treated, rate of application, number of applications, rate per crop year, pounds applied to surveyed acres and to total national crop acres. Additional file 1: Table S5 provides glyphosate herbicide data at the state level for winter wheat in Kansas from 1993–2012.

Global glyphosate use

Worldwide glyphosate use was modest in the 1970s compared to the most heavily applied herbicides then on the market (e.g. atrazine, metolachlor). The volume applied grew relatively slowly until the GE era ([27], Additional file 1: Table S24). By 1994, global agricultural use had reached 43 million kg of active ingredient (95 million pounds). Another 13 million kg were applied outside agriculture, for a total of 56.3 million kg (124 million pounds).

Use on GE-HT crops

For over a decade, the vast majority of hectares planted to maize, soybeans, canola, and cotton have been genetically engineered (GE) to be herbicide-tolerant (HT) (see Fig. 2a; [15, 16, 17]). In 2012, 265 million kgs of glyphosate were applied on GE-HT soybeans, or about 73 % of all glyphosate applied on GE-HT crops, and 41 % of total, global GBH use (Table 6). Between 2010 and 2012, glyphosate use rose moderately in GE-HT cotton production (10 %) and soybeans (19 %), but more sharply in GE-HT maize (47 %) and canola (36 %).

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Table 6

Glyphosate use on herbicide-tolerant (HT) crops and all crops

	2010	2011	2012
Cotton	8.6	11.8	9.5
North America	5.64	6.99	6.32
Rest of world	3.00	4.8	3.1
Maize	47.7	65.6	70.2
North America	26.1	28.5	31.0
Rest of World	21.63	37.1	39.2
Soybeans	223.7	239.1	265.1
North America	41.9	42.0	43.6
Rest of world	181.7	197.1	221.5
Canola	13.7	16.5	18.6
North America	0.4	0.3	0.5
Rest of world	13.3	16.2	18.1
Global use on HT crops	293.7	333.0	363.4
Global use on All crops	578.1	616.8	648.6
Percent use on HT crops (%)	51	54	56

Data are millions of kilograms of glyphosate active ingredient

National Agriculture Statistic Service, International Service for the Acquisition of Agri-biotech Applications, and Meyer and Cederburg (2010). See Additional file 1: Table S23 for details

The percent of global agricultural glyphosate use accounted for by GE-HT crops rose from 51 % in 2010 to 56 % in 2012 (Table 6). This percentage cannot be calculated accurately for earlier years because comprehensive ISAAA time series data reporting on hectares planted to GE-HT crops began in 2010 [14].

Volume applied in the U.S

The United States has the world’s most complete, publicly accessible data on glyphosate use. The combination of NASS, EPA, and USGS glyphosate use data provides a solid foundation to track trends in agricultural, non-agricultural, and total glyphosate use from commercial introduction through 2014. A report issued by the National Center for Food and Agricultural Policy [40] provides useful, detailed information on glyphosate use by state and crop for 1995, drawing on NASS, EPA, and information from land grant university weed management specialists.

Annual agricultural glyphosate use volumes in the nine EPA pesticide use reports issued between 1997 and 2007 exceed NASS annual totals for the same years by 20–70 %, largely because EPA had access to multiple data sources that made it possible to estimate the volume of glyphosate applied on all crops, as well as non-crop use patterns (e.g., pasture and range uses). NASS estimates, on the other hand, were limited in any given year to the crops surveyed in a particular year, and NASS never or rarely surveys pesticide use on crops grown on limited acreage. The differences are largest in the first two decades of glyphosate use (through 1995), and reflect the array of glyphosate uses not covered in NASS, crop-by-crop pesticide use surveys. But as total agricultural use rises sharply post-1996 in the wake of the introduction of GE-HT crops, glyphosate use on the major GE crops (maize, soybeans, cotton) is fully captured in NASS, EPA, and USGS data. Differences in agricultural use estimates between the datasets all but disappear by 2007 (NASS, 184.2 million pounds glyphosate use; EPA mid-range, 182.5; USGS, 183.2; [27], Additional file 1: Table S18).

Factors driving use upward

Several factors have driven the increase in glyphosate use since commercial introduction in 1974. In terms of area treated, the dominant factor has been the commercialization of GE-HT crops. Not only has glyphosate been sprayed on more hectares planted to HT crops, it has also been applied more intensively—i.e., more applications per hectare in a given crop year, and higher one-time rates of application [13, 28].

In the U.S. soybean sector, the average number of glyphosate applications rose from 1.1 per crop year in 1996 to 1.52 in 2014, while the one-time rate of application rose from 0.7 kg/hectare (0.63 pound/acre) to 1.1 kg/hectare (0.98 pound/acre) in the same period ([27], Additional file 1: Table S2). Shifts in weed communities favoring species less susceptible to glyphosate, coupled with the emergence of first, less sensitive, and eventually glyphosate-resistant weeds drove the incremental rise in the intensity of glyphosate applications on GE-HT crops [13, 10]. Rising reliance on glyphosate by soybean producers in the U.S. is graphically portrayed in Fig. 1a, while Fig. 1b shows modest change during the GE era in soybean yield/acre or production per soybean seed planted. Steady increases in the number of applications of glyphosate, rate per crop year, and glyphosate’s share of overall soybean herbicide use are shown in Fig. 1c.

Other factors contributed to rising glyphosate use. These include steady expansion in the number of crops registered for use on glyphosate product labels, the adoption of no-tillage and conservation tillage systems, the declining price per pound of active ingredient (see Fig. 2b), new application method and timing options, and new agricultural use patterns (e.g., as a desiccant to accelerate the harvest of small grains, edible beans, and other crops).

The one-time average rate of glyphosate application on Kansas wheat has incrementally risen threefold, from 0.33 kg/hectare in 1993 to 0.95 kg/hectare in 2012 ([27], Additional file 1: Table S5). The trend toward no-till and conservation tillage systems has increased wheat farmer reliance on herbicides, including glyphosate. The average two applications in recent years on winter wheat could include a pre- or at-plant spray, an application during a summer fallow period, and/or a late-season application intended to speed up harvest operations (a so-called “harvest aid” or “green burndown” use) [41]. The average rate per crop year—the single most important indicator of the intensity of glyphosate use—rose even more dramatically, from 0.47 kg/hectare in 1993 to 2.08 kg/hectare in 2012 (4.4-fold).

Global use of glyphosate

Farmers worldwide applied about 51.3 million kgs (113 million pounds) of glyphosate in 1995 ([27], Additional file 1: Table S23). To place this volume of global glyphosate use in perspective, in just one country (the U.S.) that year, farmers applied ~60 million kgs (132 million pounds) of two herbicides (atrazine and metolachlor) on mostly one crop (maize) ([27], Additional file 1: Table S19).

But the scope and intensity of glyphosate use worldwide rapidly changed as GE-HT crops gained market share. There were about 1.4 billion hectares of actively farmed, arable cropland worldwide in 2014 [44]. Across this landmass, there were an estimated 747 million kg of agricultural applications of glyphosate. Accordingly, if this volume of glyphosate had been applied evenly, about 0.53 kg of glyphosate could have been sprayed on every hectare of cropland on the planet (0.47 lbs/acre).

Glyphosate was, of course, not applied evenly on every hectare of cropland. The average rate of glyphosate applications per hectare per crop year during 2014 fell in the range of 1.5–2.0 kg/hectare [27]. At these rates of application, the total volume of glyphosate applied in 2014 was sufficient to treat between 22 and 30 % of globally cultivated cropland. No pesticide in history has been sprayed so widely.

Since losing global patent protection around 2000, dozens of companies began manufacturing technical glyphosate, and/or formulating glyphosate products. Some two-dozen Chinese firms now supply 40 % of the glyphosate used worldwide, and export most of their annual production [45].

The loss of patent protection and increased generic manufacturing of glyphosate has placed downward pressure on prices since 2000 [30, 45, 46]. The major manufacturer, Monsanto, has typically not competed directly or solely on price, and instead has been successful in holding or expanding market share by bundling purchase of higher-price, Monsanto brand, Roundup herbicides with the purchase of Monsanto herbicide-tolerant seeds [45, 46, 47]. Especially in the U.S., this bundling strategy has been augmented by various volume incentives and discounts, special financing, rebates for purchase of other herbicides working through a mode of action other than glyphosate’s (to delay the spread of resistant weeds), and other non-price benefits tailored to appeal to large volume customers [46, 47, 48].

The diversity of global uses in agriculture and other sectors has grown over the past 40 years [9], making it more difficult to compile accurate global data across all glyphosate uses, especially by sector and specific use. As a result, global glyphosate use projections can only be based on industry-wide glyphosate production figures, as done from 1997–2014 in Table 4 and Additional file 1: Table S24 [27].

Impact of GE-HT technology

The development and marketing of GE, Roundup Ready crops fundamentally changed how crop farmers could apply glyphosate. Before RR technology, farmers could spray glyphosate prior to crop emergence, for early-season weed control, or after harvest to clean up late-season weeds. But with RR crops, glyphosate could also be sprayed 1–3 times or more after the crop had emerged, leaving the crop unharmed but controlling all actively growing weeds. This historically significant technological advance set the stage for unprecedented and rapid growth in the area planted to RR crops and sprayed with glyphosate (from usually less than 10 % of cotton, maize, and soybean acres pre-1996, to 90 % or more today) [47, 49, 50].

The interplay of various factors leading to increased glyphosate use is apparent in Fig. 2a, which shows the trend in overall glyphosate use on the key GE-HT crops in the U.S., the correlation between reductions in average price per pound and use (Fig. 2b), and rising use and the emergence of resistant weeds (Fig. 2c).

Use of glyphosate on some GE-HT crops may have declined, or may soon begin declining in some regions because (a) adoption of GE-HT soybeans, cotton, and canola has peaked in most of the countries that have embraced GE technology [9], and (b) farmer willingness to pay for repeat applications of glyphosate, or further increase application rates, typically declines as glyphosate-resistant weeds become well established, as they have in much of the U.S. [13] and in Brazil and Argentina [10]. On the other hand, GE-HT crops may move into some regions not previously planting them (e.g., China), and reductions in the price of generic glyphosate herbicides could lead to more intensive use in some countries.

In the countries that have planted the largest shares of GE-HT crops (the U.S., Argentina, and Brazil), glyphosate use rates per hectare per crop year have risen sharply since around 2000 [20, Additional file 1: Tables S2, S3, S22]. Worldwide on GE soybean and cotton, average total herbicide use per crop year per hectare has approximately doubled from 1996 to 2014, with the increase in glyphosate volumes applied per hectare accounting for nearly all of the per hectare increase. Maize herbicide use per hectare has risen modestly, if at all, in large part because adoption of GE-HT maize hybrids allowed farmers to reduce reliance on a half-dozen other widely used maize herbicides applied at relatively high rates (e.g., ~1 kg/hectare per crop year) [11].

Because GE-HT soybeans account for two-thirds of the total hectares planted to GE-HT crops worldwide, the doubling of average herbicide use per hectare of HT soybeans drives the sizable increase in overall herbicide on all GE crop hectares. There is, as well, a clear connection throughout South America in the adoption of GE-HT technology and no-tillage systems [17, 38]. No-till farming in South America lowers machinery and labor costs, and reduces soil erosion, but at the expense of heightened reliance on herbicides for weed control, and other pesticides to control insects and fungal pathogens.

Despite gaps in publicly accessible data, the dramatically upward trajectories in glyphosate use in the U.S. and globally are unmistakable. In the pre-GE era (1974–1995) in the U.S., non-agricultural glyphosate uses accounted for ~34 to 42 % of total use. The share of total glyphosate use accounted for by the agricultural sector shifted markedly upward post-1996, starting at 66 % in 1996 and reaching 81 % 5 years later (2001) and 92 % by 2014 ([27], Additional file 1: Table S18).

The total volume of use and the split between agricultural and non-agricultural uses in the pre-GE era period are subject to greater uncertainty than in the 1996–2014 period. However, pre-1995 glyphosate use is minor compared to the post-GE period, when both data quantity and quality improved, especially covering applications in the U.S. and on global GE-HT hectares planted.

Figure 3 arrays milestones in the history of glyphosate discovery, commercialization, and regulation, while Fig. 4 displays key events in the history of glyphosate use and impacts.

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Rising use triggers new concerns

Driven by the growing diversity of uses and dramatic increases in volumes applied, levels of glyphosate and its primary metabolite aminomethylphosphonic acid (AMPA) have been detected in the air [51], soil [52], and water [49, 53]. With few exceptions though, contemporary levels of glyphosate in the air, water, and food result in typical human exposure estimates that remain well below the “levels of concern” or “Acceptable Daily Intakes” established by regulatory bodies around the world.

Still, a growing body of literature points to possible, adverse environmental, ecological, and human health consequences following exposure to glyphosate and/or AMPA, both alone [54] and in combination with ingestion of GE proteins (e.g., EPSPS, Bt endotoxins) [55]. Environmental studies encompass possible glyphosate impacts on soil microbial communities and earthworms [56, 57, 58], monarch butterflies [59], crustaceans [60], and honeybees [61].

Studies assessing possible risks to vertebrates and humans include evidence of rising residue levels in soybeans [62, 63], cancer risk [64], and risk of a variety of other potential adverse impacts on development, the liver or kidney, or metabolic processes [54, 55, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80].

Relative toxicity and impacts

For years, glyphosate has been regarded as among the least chronically toxic herbicides for mammals, and indeed only three EPA-registered synthetic pesticides in current agricultural use have a higher chronic Reference Dose (the imidazolinone herbicides imazamox, imazethapyr, and imazapyr).

For human exposures, the U.S. EPA has set glyphosate’s daily chronic Reference Dose (cRfD) at 1.75 milligrams per kilogram of bodyweight (mg/kg bodyweight/day). The EU-set cRfD for glyphosate was recently raised from 0.3 to 0.5 mg/kg/day, 3.5-fold lower than EPA’s. A team of scientists has compiled evidence supporting the need for a fivefold reduction in the EU cRfD to 0.1 mg/kg/day [81], a level 17-times lower than EPA’s.

Glyphosate is a moderate dose herbicide with relatively low acute and chronic mammalian toxicity, to the extent mammalian risk is accurately reflected in required EPA toxicology studies. After an exhaustive review, however, glyphosate was classified in 2015 as a “probable human carcinogen” by the International Agency for Research on Cancer [64], based on increased prevalence of rare liver and kidney tumors in chronic animal feeding studies, epidemiological studies reporting positive associations with non-Hodgkin lymphoma, and strong mechanistic evidence of genotoxicity and ability to trigger oxidative stress [64].

The body of toxicological studies supporting glyphosate’s current EPA and EU cRfD, and hence all contemporary uses of this herbicide, dates back to the early 1970s through mid-1980s [82]. Recent studies suggest that glyphosate in its pure form, and some formulated glyphosate end-use products, may be triggering epigenetic changes through endocrine-mediated mechanisms [54, 73, 75, 76, 79, 81, 83].

Evidence from multiple studies suggests that the kidney, and secondarily the liver, is at risk of glyphosate-triggered, or glyphosate-enhanced chronic degeneration [55, 71, 72, 84, 85]. Industry metabolism studies in farm animals, rats and mice, and rabbits were conducted in the 1970s and 1980s, and show that in animal feeding studies, glyphosate levels in the kidney usually exceed those in the liver by three- to tenfold, and those in the liver exceed levels in other tissues by a wide margin [86].

The apparent tendency of glyphosate to concentrate in the kidneys, coupled with glyphosate’s action as a chelating agent, has led some scientists to hypothesize that glyphosate can bind to metals in hard drinking water, creating metallic-glyphosate complexes that may not pass normally through kidneys [71, 72]. For this, or other as yet unrecognized reasons, the risk of chronic kidney disease may be heightened in human and animal populations with heavy glyphosate exposure.

The IARC classification and emerging evidence relative to kidney damage and endocrine effects heightens the need for, and will complicate ongoing and future glyphosate worker and dietary-risk assessments. Annual residue tests are carried out by the U.K. Food Standards Agency (FSA). Residues of glyphosate were found in 10–30 % of grain-based samples from 2007–2013, at generally rising levels [87]. Glyphosate and AMPA residues are present at relatively high, and rising levels (over 1 ppm) in a high percentage of the soybeans grown in the U.S., Canada, Brazil, Argentina, Paraguay, countries which account for 86.6 % of the 11.6 billion bushels of soybeans produced globally in 2014, and nearly all global trade in soybeans and soybean-based animal feeds [34, 62].