Made by the Monsanto Corporation, Roundup is one of the world’s most widely used herbicides. Almost a billion kilograms of it and its chemically-similar relatives are applied annually on crops, gardens, sidewalks and lawns by farmers and homeowners alike.

It is also used by drug enforcement agents globally in the fight against illegal crops like marijuana and coca, and even by some environmental groups for invasive species eradication and habitat restoration. In addition, many of the genetically-modified crops that are grown commercially are specifically engineered to resist Roundup; nine-tenths of the corn, cotton, and soybeans produced in the US are “Roundup Ready” (i.e. herbicide resistant) strains created and patented by Monsanto scientists. Monsanto makes an estimated $5 billion annual from the sale of Roundup and Roundup Ready-plants.

When glyphosate, the active ingredient in Roundup and similar herbicides, was first discovered in 1970 it was called a “virtually ideal” herbicide. The chemical kills plants and other affected organisms by inhibiting an enzyme tongue-twistingly called 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). This enzyme is essential for the synthesis of three amino acids: phenylalanine, tyrosine, and tryptophan.

Because EPSPS is produced by plants and microbes but not animals, glyphosate is considered to be largely safe. Initial laboratory studies, for example, found that the LD50 (or Lethal Dose 50, a laboratory measure of a chemical’s toxicity) of glyphosate was 5,000 milligrams (mg)/kilogram (kg) for rats, 10,000 mg/kg for mice and 3,530 mg/kg for goats. It also appeared to have relatively low carcinogenicity and reproductive toxicity in animal studies.

As a result, Roundup and other glyphosate-containing herbicides are classified as safe for human use and consumption by regulatory authorities like the US Environmental Protection Agency (EPA).  The US EPA set the acceptable daily intake (ADI) for glyphosate at 1.75 mg/kg of bodyweight per day. This means that a 176-pound (80-kg) man like myself can safely consume 140 mg of glyphosate each day and every day with no ill effects.

It turns out, however, that classifying herbicides like Roundup as safe to use might have been a bit premature. While most of the early laboratory studies suggested that glyphosate had low toxicity, more recent laboratory studies using the complex formulations of glyphosate and other so-called ‘inert’ ingredients that comprise the actual herbicide that is sprayed widely on our fields, lawns, and flowers suggest that these commercially-available products are much more toxic than glyphosate alone. One study found that Roundup can cause liver and kidney damage in rats at only 0.05 ppb (parts per billion, equivalent to about 1 microgram/kg), well below the LD50 of 5,000 mg/kg previously reported. A similar study of aquatic animals found that levels as low as 10 ppb can have toxic effects on the livers of fish.

Moreover, some epidemiological studies to show potential links between the use of these herbicides and diseases like lymphoma (although these implications of these data are still unclear). These findings lead the International Agency for Research on Cancer (part of the World Health Organization) to declare glyphosate as “probably carcinogenic in humans”, and similarly lead some countries to lower their exposure limits.

More importantly, even if you do not use Roundup or other herbicides at home, it is possible that you are being exposed to it through the foods you eat. Laboratory testing of 29 common foods by the non-profit organization Food Democracy Now found detectible residues on most. Glyphosate residue were found in popular cereals like Cheerios (1,125.3 ppb), Honey Nut Cheerios (670.2 ppb), Raisin Bran (82.9 ppb), Corn Flakes (78.9 ppb), and Wheaties (31.2 ppb). Crackers like Ritz and Triscuit were also contaminated, with residues of 270.24 and 89.68 bbp respectively, as were cookies like Oreos (289.47 bbp) and even “healthy” food company Kashi’s soft-baked oatmeal cookies (275.57 ppb).

Of course, those of us who are relatively health conscious rarely eat processed foods like these. Nevertheless, we are still exposed to glyphosate-containing herbicides through the produce that we buy in the store. Just last week the nonpartisan Environmental Working Group released a list ranked pesticide contamination in 47 popular fruits and vegetables. The so-called ‘dirty dozen’ topping the list included, in order of contamination, strawberries, spinach, nectarines, apples, grapes, peaches, cherries, pears, tomatoes, celery, potatoes, and sweet bell peppers.

In fact, glyphosate is present at all levels of the modern food chain. A study of tap water conducted by Moms Across America and by Sustainable Pulse found it in nearly half of all samples tested, at levels of up to 0.3 ppb (albeit well below the US EPA’s allowable limit of a whopping 700 ppb, which is also the level that causes measurable changes in the livers and kidneys of laboratory rats). Because many commercially-raised farm animals are fed Roundup Ready crops like soybeans and corn, glyphosate has also been found at levels exceeding 10,000 ppb in the organs and meat of cows and pigs.

It should be no wonder then that research conducted at the University of California at San Francisco and elsewhere has found glyphosate in the urine of healthy human volunteers. Overall, 50% of people tested had detectable glyphosate in their urine, with an average concentration of 12.6 ppb. When a similar study was conducted in a farming community in Iowa, 95% of the children tested had glyphosate in their urine. Interestingly, in many of these studies those who were suffering from self-reported chronic illnesses had, on average, higher levels of glyphosate in their urine.

These data are extremely alarming, as is the reluctance of the responsible government agencies in the US and elsewhere to reconsider what constitutes safe use of Roundup and other glyphosate-containing herbicides. Until then, health conscious people need to carefully consider their food and drink choices in order to reduce their exposure to this potential dangerous but sadly ubiquitous chemical. This includes avoiding common GMO foods like soy and corn, non-organic cereals and grains treated with glyphosate, processed foods known to be high in glyphosate like breakfast cereals, crackers and cookies, using a filter that removes contaminants like glyphosate from tap water, and either avoiding or vigorously washing (for 30 seconds or more under running filtered water) any commercially-grown vegetable likely to have been treated with pesticides.