Glyphosate should be banned to reduce harmful cyanobacterial blooms and red tides

Glyphosate is the “so-called” active chemical ingredient in Roundup herbicide as well as many other name brand glyphosate-based weedkillers. Glyphosate based herbicides are the most widely used in the world and glyphosate use has increased almost 15-fold in the last 20 years. (Benbrook 2016)  Glyphosate is a phosphonate-based herbicide which requires phosphate mining. (Dissent 2017)  The process by which glyphosate is made has led to a superfund site due to radioactive waste materials, groundwater pollution and mercury emissions. (Dissent 2017)  Glyphosate is a broad spectrum nutrient and mineral chelator (Johal 2009); an endocrine and hormone disruptor (Gasnier 2009, Myers 2016); a patented antibiotic ((United States Patent 7,771,736) that is sprayed on GMO food crops; used as a ripening/drying agent on non-organic crops such as wheat, legumes, sugar, nuts, seeds; sprayed on lawns, sidewalks, children’s parks and schools; and is found in our waterways, rainwater, soil & air.(Majewski 2014, Battaglin 2014).

Glyphosate’s role in harmful cyanobacterial blooms and Red Tide.

Harmful cyanobacteria such as Microcystis aeruginosa are naturally resistant to glyphosate and low levels of glyphosate in a water body stimulates the growth of Microcystis aeruginosa which can cause blooms.(Zhang 2016) Since Microcystis aeruginosa is resistant to glyphosate

glyphosate inhibits the growth of other phytoplankton which would normally compete with Microcystis aeruginosa for nutrients.  This further allows Microcystis aeruginosa to flourish in the presence of glyphosate.(Harris 2016)  Florida Fish and Wildlife have repeatedly sprayed in and around Lake Okeechobee with glyphosate-based herbicides such as Roundup Custom, Rodeo and Aquaneat(Florida Fish and Wildlife 2015, Florida Fish and Wildlife 2016)  Glyphosate can also find its way into water bodies even when not directly applied to water through runoff.(Majewski 2014, Battaglin 2014)  Once Microcystis aeruginosa blooms occur this cyanobacteria can spread not only through connecting waterways, but also through an airborne route.(Lee 1989)  This means that areas which are not connected by water to a source of Microcystis aeruginosa can still be contaminated even if it is miles away. Since Microcystis aeruginosa spreads through the air it could find its way into other water bodies.  If these other water bodies have also been sprayed with glyphosate based herbicides it could also stimulate the growth of Microcystis aeruginosa which can cause blooms in these other water bodies.

Trichodesmium is saltwater cyanobacteria found in the Gulf of Mexico and can sometimes be found in the Atlantic Ocean off the coast of Florida. Trichodesmium fixes nitrogen so it provides nutrients that increases the growth of Karenia brevis which is responsible for red tides.(Mulholland 2006)  Like Microcystis aeruginosa, Trichodesmium also uses glyphosate as a source of phosphorus.(Dyhrman 2006)  Therefore, the use of glyphosate by Trichodesmium can lead to saltwater cyanobacterial blooms which leads to an increase in nitrogen which then causes Karenia brevis blooms which leads to red tides.

Harms from Microcystis and glyphosate.

Microcystis aeruginosa produces cyanotoxins such as microcystins and BMAA .  Exposure to these cyanotoxins may cause harmful effects such as non-alcoholic fatty liver disease(Albadrani 2017) and cancer.(Hernández 2009)  Since toxins from Microcystis aeruginosa can be spread through the air and find their way into drinking water all people within several miles of a Microcystis aeruginosa bloom will likely be exposed to the cyanotoxins.

Like Microcystis aeruginosa, studies have also reported exposure to glyphosate-based herbicides can cause kidney and liver damage including the potential for non-alcoholic fatty liver disease, in some cases at glyphosate levels as low as .05 parts per billion. (Abarikwu 2015, Benedetti 2004, Seralini 2014, Mesnage 2015, Mesnage 2017).  Glyphosate-based herbicides have also been linked to cancer.  The International Agency for Research on Cancer (IARC), the specialized cancer agency of the World Health Organization (WHO), concluded that there is sufficient evidence of glyphosate’s carcinogenicity in experimental animals and classified glyphosate as probably carcinogenic to humans (International Agency for Research on Cancer 2015). A jury in U.S. federal court in California delivered a $289 million verdict against Monsanto, the primary manufacturer of glyphosate-based herbicides, on behalf of a school groundskeeper who developed non-Hodgkins lymphoma after repeated exposure to Monsanto’s Roundup herbicide. The verdict stated Monsanto acted with malice failing to warn of the risk of developing non-Hodgkin’s lymphoma, a form of cancer, from exposure to glyphosate. Currently about 8,700 other people diagnosed with Non-Hodgkin’s Lymphoma after being exposed to a glyphosate-based herbicide are also suing Monsanto. (CBS/AP 2018, Marketwatch 9/5/2018).

Glyphosate exposure may also reduce testosterone levels (Clair 2012, Abarikwu 2015), impair sperm quality (Abarikwu 2015, Owagboriaye 2017), or cause disturbances in the reproductive development when exposed during puberty (Romano 2010).  Along with an increase in glyphosate use there has been a 500% average increase in the level of glyphosate found in human urine. (Mills 2017) One study found higher urinary glyphosate levels in pregnant women was associated with a shortened gestational length which is associated with a reduction in lifetime cognitive achievement (Parvez 2018). Another study observed humans that were chronically ill had significantly higher glyphosate residues in their urine than their healthy counterparts (Kruger 2014).

Environmental harms from Microcystis and glyphosate.

Studies have observed harm to aquatic organisms, such as fish, from both glyphosate and cyanotoxins from Microcystis aeruginosa.(de Freitas Goncalves 2017, Glyphosate Studies)  Other aquatic organisms such as amphibians may also be harmed by both glyphosate and cyanotoxins from Microcystis aeruginosa at low levels.(Zhang 2013, Glyphosate Studies).  Glyphosate based herbicides have been a major contributor in the reduction of the monarch butterfly and has been shown to alter bee behavior.(Glyphosate Studies) Glyphosate based herbicides can also harm beneficial insects such as the green lacewig and two spotted ladybug.(Glyphosate Studies) Other beneficial organisms such as several spiders and earthworms are also adversely impacted by glyphosate based herbicide use.(Glyphosate Studies)

Banning or restricting glyphosate

In Florida Hallandale Beach recently adopted a resolution to ban glyphosate from the city level.  The city of North Miami passed a resolution to severely restrict glyphosate and other harmful pesticides. (North Miami 2017)  To accomplish this the city adopted the San Francisco Hazard Tier which only allows the least harmful pesticides to be used regularly and severely restricts the use of harmful pesticides.(San Francisco Hazard Tier)  In Miami Beach City a resolution was passed to ban glyphosate use on all city-owned properties.(Community News 2018)  Other Florida cities such as Venice(Herald-Trubune 2018) and Stuart(WFLX 2018) are working towards banning or restricting glyphosate as well.  Numerous other countries and cities have also banned or severely restricted glyphosate(Baum Hedlund 2018)

Alternatives to glyphosate

Mechanical methods for above ground use would include flame weeding, steam weeding and foam weeding.  Also rotary cultivators work as does a basic scuffle hoe.  Chemical methods include the use of vinegar for certain plants.(Moms Across America 2018)

Alternative methods to the use of glyphosate-based herbicides for reducing weeds in a water body depend on the conditions.  If the weeds are above the surface of the water control could be accomplished with mechanical, biological, chemical and physical methods.  Mechanical methods could include the use of small cutting boats.  Although these cutting boats are initially expensive, in the long-term these boats are often more cost effective than glyphosate-based herbicides.  Glyphosate based herbicides must be applied several times per month depending on the conditions.  Over time this continuous use of glyphosate based herbicides leads to herbicide tolerant weeds meaning larger and larger doses must be used to kill weeds,and as previously mentioned this could increase the amount of harmful cyanobacteria in waterways.

In comparison cutting boats function like lawnmowers where weeds never become immune to being cut and would not increase cyanobacteria.  A local Florida company selling small cutting boats would be Weedoo Greenboat( ).  Less expensive weed cutters can be attached to already existing boats such as the Aquatic Mower( ).  Also, dock or frame-based weed cutters can be used such as the Lake Groomer( ).

Biological methods would depend on the type of weeds growing in the water body.  Depending on the weeds this could include stocking the pond with plant-eating fish such as triploid grass carp.  Chemical methods would also depend on the species of weeds in the water body.  Species such as Hydrilla verticillata, Stuckenia pectinatus, and Spartina alterniflora can be controlled with vinegar(4%-20% acetic acid) based herbicides(Anderson 2007).  The EPA allows vinegar(up to 8% acetic acid) to be added to a formulation as an “inert ingredient”(EPA 2016).  Even if a 20% acetic acid solution were used there is a part of federal law which states that if a product clearly has uses other than as a herbicide and no claims about that product having herbicidal uses are made, it does not have to be registered.  Acetic acid has numerous other uses so it falls under this category.  The MSDS for vinegar at 7% acetic acid indicates LD50(oral,rat) = 47286 mg/kg.(MSDS Vinegar) In comparison the World Health Organizations indicates for glyphosate LD50(oral,rat) = 4230 mg/kg(World Health Organization 2004). Therefore, vinegar is far less acutely toxic than glyphosate and homeowners would be very happy to know that vinegar(at 7% acetic acid) is >10 times less acutely toxic than glyphosate.  Even at 20% acetic acid the MSDS indicates Acute Oral LD50 (Rat): >5,000 mg/kg

(MSDS Horticultural Vinegar) which is still not as acutely toxic as glyphosate.  However, this still does not take into consideration that in most cases pure glyphosate is not used and formulations, such as Roundup, which include glyphosate as the active ingredient tend to be more toxic than glyphosate by itself.(Mesnage 2014, Benachour 2008)  Also, this does not consider the toxicity of AMPA(aminomethyl-phosphonic acid), a metabolite of glyphosate, which is considered even more toxic than glyphosate.(Benachour 2008)

If you’re interested in a viable, non-toxic, alternatives to glyphosate (Roundup) and other harmful pesticides and best practices, please reach out to Chip Osbourne.  Chip will come to your city to help.

Chip Osbourne
Board member of Beyond Pesticides – A huge resource

If the weeds are below the surface of the water, permanent control of weeds can be achieved with barriers.  These function by blocking light to the plants, stopping photosynthesis, killing the weeds. These include examples such as LakeMat Pro ( ) which float above the surface of the water, or Lake Bottom Blanket ( ) which float above the benthos layer of the lake.  This can provide permanent weed control for smaller water bodies.

What can you do?

Stop using glyphosate-based herbicides and urge your neighbors, friends and relatives to do so as well.  Contact your city council members and ask them to ban or severely restrict glyphosate use on city-owned properties.  This can be done by adopting a resolution similar to North Miami.(North Miami 2018)  Contact local stores that sell glyphosate-based herbicides such as Lowes and Home Depot and urge them to stop selling it.  Costco just eliminated Roundup from their shelves! Buy organic food which does not allow glyphosate to be used.

Help us ban glyphosate in FL


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MSDS Horticultural Vinegar

MSDS Vinegar

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San Francisco Hazard Tier

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