Glyphosate Monitoring Strategy
The Glyphosate Monitoring Strategy aims to monitor the risks of exposure to glyphosate, its degradation products and associated surfactants used in the herbicides Rodeo ® and Roundup ® and to consider the ecotoxicity in the environment.
The following shall be analysed for glyphosate, as well as the degradation products and surfactants used in Rodeo ® and Roundup ®:
- Groundwater
- Air within the vehicle cab of the glyphosate applicator truck
- Air from behind the glyphosate applicator vehicle
- Roadside soils and pond sediments
- Genetically Modified food stuffs from supermarket shelves
It has taken the Department considerable effort to date to identify analytical laboratories that can determine all analytes (glyphosate, derivatives and surfactants) at the required detection limits in all the matrices listed above.
It is estimated that the sampling will start in June 2016 and will be completed by end of July 2016.
Background Information
In March 2015 the World Health Organization (WHO) changed the associated risk category of glyphosate-based formulations from ‘Possible Carcinogen’ to ‘Probable Carcinogen’ to humans.
As a result of pressure from the public and following various stakeholder meetings, the Minister of Health, Seniors & Environment suspended the importation of glyphosate to Bermuda in May 2015.
During the suspension, officers of the Bermuda Government were to conduct a range of analyses to understand the level of risk to the public from a variety of potential exposure pathways.
In November 2015 the European Food Safety Authority (EFSA), reported that glyphosate (only) is unlikely to pose a carcinogenic hazard to humans and has proposed a new safety measure that will tighten the control of glyphosate residues in food.
What is Glyphosate?
Glyphosate is a herbicide. The largest use worldwide is in agriculture. The agricultural use of glyphosate has increased sharply since the development of crops that have been Genetically Modified (GM) to make them resistant to glyphosate. It can also be applied to non-GM crops just before harvest to aid as a desiccant. Glyphosate is applied directly on these crops. Glyphosate is also used in forestry, urban, and home applications.
Bio-concentration of glyphosate in aquatic organisms is low and glyphosate is not suspected of being an endocrine-disrupting chemical. Although glyphosate is readily soluble in water it undergoes rapid ionization causing it to be strongly adsorbed to sediments and soils3. Glyphosate degrades to natural products such as carbon dioxide and phosphate ions predominantly via microbial processes. It is rapidly removed from water to sorption sites on sediments and suspended particulate matter3.
Previous Glyphosate Data for Bermuda
The Department of Environment and Natural Resources has contracted research through the Bermuda Zoological Society, who in turn hired Fort Laboratories Inc. in Oklahoma to assess pollutant exposure and its effects on critical groups in ponds in Bermuda (i.e. toads, killifish and terrapins). This work assessed a wide range of pollutants that included pesticides and herbicides.
Over the 2001 to 2013 timeframe glyphosate was not detected in pond sediments (<0.5µg/kg), water column (<0.05 µg/l), SPMD’s in the road drainage pipes nor in tissues of the animals dissected. Glyphosate is also routinely monitored, with other chemicals in the Government drinking water sources and distribution mains and it has not been detected to date (i.e. <10 µg/l).
Why test these types of samples for glyphosate?
- Groundwater
Due to Bermuda’s high permeability limestone and high rainfall, chemicals applied at the ground surface may rapidly make their way to the water table and affect groundwater. Treatment of groundwater by reverse osmosis (i.e. to produce potable grade water) will be expected to remove most of the glyphosate or residues that may be present in the feed water.
Although it is illegal to fill potable water tanks from untreated groundwater sources in Bermuda (i.e. from wells) there is a risk that this practice may occur. In addition, groundwater from wells may be used for irrigation, laundering and swimming pool supply, providing other exposure pathways. For this reason, in addition to understanding the ecotoxicological impact to water borne species, it is necessary to analyse Bermuda groundwater for glyphosate and associated residues.
However, understanding what concentration limit to apply for glyphosate in Bermuda will be a challenge. WHO has not set a guideline limit as glyphosate and degradation products occur in drinking water well below the levels where toxic effects may occur. The EU limit for glyphosate (or any pesticide, herbicide, etc.) is 0.0001 mg/l (i.e. 0.1µg/l) and the US drinking water limit for glyphosate is 0.7 mg/l, Canada 0.28 mg/l and Australia 0.01 mg/l.
This wide range of legislated drinking water limits from various developed countries is not consistent and highlights that the understanding of glyphosate toxicity to humans is not agreed nor understood.
- Air Samples
Locally, glyphosate is typically applied as weed control to roadsides and other areas but not to any crops as farmers do not grow GM crops in Bermuda nor do they use it as a pre-harvest desiccant. Persons that are most likely to be exposed to glyphosate from roadside spraying include the operator of the herbicide spraying vehicle (Ministry of Public Works) and potentially persons waiting, walking or driving along the roadside behind the applicator truck.
In one study it was reported that glyphosate exposure was not associated with cancer incidence overall for herbicide applicators. Currently in the US there is no OSHA (US Occupational Safety & Health Administration) permissible exposure limit (PEL) or ACGIH (American Conference of Governmental Industrial Hygienists) threshold limit value (TLV) for glyphosate.However, an arbitrary limit of 1 mg/m3 (method PV2067) has been set by OSHA, which will be used as the threshold for this study.
In Europe there are also not any defined occupational exposure limits for glyphosate.It will therefore not be possible to relate the inhalation exposure of glyphosate in Bermuda to any specific international occupational exposure limits. Also the occupational exposures are unlikely to be much lower than the WHO Acceptable Daily Intake (ADI) limit (see foodstuffs below).
- Foodstuffs
There appear to be a limited number of independent peer reviewed publications that have highlighted glyphosate residues within GM crops and also in non-GM crops from pre-harvest application.One study has shown that the glyphosate intake from cereals in Denmark for an adult of 60kg equated to 7 µg/day, which is only 0.04% of the WHO Acceptable Daily Intake (ADI) for glyphosate at 0.3 mg/kg body weight. However, it is not stated whether the glyphosate (761 tons used in 1999 in Denmark7) was applied as a general weed killer in Denmark or whether it was applied specifically to GM-type or other crops grown for human consumption that were subsequently harvested.
Although GM crops are not grown in Bermuda most of the Island’s produce is sourced from the US where GM cereals and glyphosate application are more common (Figure 1). Analysis of glyphosate residues in some food stuffs (i.e. corn maize, wheat, flour) on shelves in Bermuda that are sourced from the US (mid states) will be conducted to assess whether any level of risk exists to Bermuda residents.However, sourcing suitable food stuffs for testing in Bermuda may present a challenge because labelling of GM food stuffs is not required in the US.
Figure 1. US Geological Survey: Estimate of Agricultural use of Glyphosate (2013)
[1] Granby, K and Vahl, M (2001). Investigation of the herbicide glyphosate and the plant growth regulators chlormequat and mepiquat in cereals produced in Denmark. Food Additives and Contaminants, Vol. 18, N.10.
[1] Estimated agricultural use of glyphosate in the US in 2013. USGS. National Water-Quality Assessment (NAWQA) Program: https://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2013&map…