Are the vegetables sold in Sri Lankan markets full of Toxic Pesticides?
Posted on November 7th, 2018

Chandre Dharmawardana, Ottawa Canada

According to a news report, a scientific meeting of the Dept. of Agriculture (DOA)  was held in Peradeniya on the 6th and 7th   of September 2018 on  Agriculture beyond production”. One aspect  of this topic was bringing farm produce to the consumer with the minimum of waste. It is well known that 40% to 60% of agricultural products get wasted, attacked  by bugs, microbes, vermin etc.,  and become rotten before it reaches the market, especially in tropical countries. Another aspect of this study was an evaluation of potentially toxic  pesticide residues found in vegetables.

A journalist writing in the Irida Divaina ( claimed that the The bundle of leafy vegetables has got fire in it- there is danger hidden in Gotukola and Mukunuwaenna. Sometimes 700 times more than the safe limit of pesticide residues are found in these vegetables. Farmers spray poison even before the plants get sick”. We explain that the above declaration of danger to health  is  a false alarm.

Concern about toxins” in food has been sharpened by the organic food movement. It is currently in a global  market struggle to capture supermarket space for its products. Here the upper-class elites who adopt Californian concerns,  and the romantic traditionalists who claim a golden past”  have joined hands. They espouse organic food”,  and seek  a Toxin-Free Nation” even in Sri Lanka by adopting many myths of Western green” activists. They have their own myths too – ancient Lankans were well-fed and lived long, Methuselah-like, using only traditional agriculture without pesticides and fertilizers, except for natural fertilizers”.  They ignore the written record of multiple famines, and the record of sequential droughts seen in the rings of South-Asian tree trunks studied by dendro-climatologists. The heady claim that Lanka was the granary of the East is a literal truth to these romantics. In reality, the common people teetered between subsistence and famine, while only the palace and temple had it  good.

Given the heightened concern about  pesticide residues in food, the presentation by  Ms. Y. Lakshani, a scientist from the laboratory of the Registrar of pesticides has attracted media interest.

The study was in collaboration with J.A. Sumith, K. Rajapaksha, B. Bambaradeniya and T. Chathurangi from Wayamaba University. Popular leafy vegetables like Gotukola (Centella asiatica) and Mukunuwenna (Alternanthera sessilis) grown in Kalutara, Puththalama (Puttlam) and Nuwara (Kandy) districts had been tested;  residues of four popular pesticides were found in 50% of the samples, most of which came from the Puththalama area, with the Kandy district coming second.

Four insecticides were found in significant quantities in vegetables. Of these, the most significant amounts were for the insecticide  Prifenofos and the fipronil.

  1. fipronil is used to control ants, beetles, cockroaches, fleas, ticks, termites, mole crickets, thrips, rootworms, weevils, and other insects. The maximum allowed limit (MAL) on this insecticide residue on leafy vegetables is five parts per billion (ppb) in some countries. That is,  only one tea spoon of the residue finely distributed in one thousand metric tons of the vegetable is allowed! On the other hand, the US limit is one ppb, while twice as much is allowed in tea, and 10 times as much are allowed on rice! Does the pesticide become ten times less toxic when found in rice?

No at all. The maximum allowed limit quoted is NOT a measure of toxicity;  it is a measure of good farming practice (GFP), with differing  GFP based MALs for different crops, and in different countries. The public, journalists, Green-Lobby groups like the AVAAZ team, and even many medical doctors who write about public health matters do not understand that this MAL has nothing to do with toxicity.

While the Dept. of Agriculture  is interested in ensuring GFP, scientists should  instruct reporters to use these numbers correctly. They should not use these tiny ppbs  to fan public fear.  What they need is not the GFP-MALs, but the admissible daily intake (ADI)  for chronic toxicity arising from the ingestion of such insecticide residues. These are stipulated jointly by the WHO and FAO. Chronic toxicity is the form of slow poisoning that occurs if you take a small amount of a substance for many years. If the intake is less than the ADI, then there is no health risk.

The WHO-FAO (Sept. 2016) ADI of fipronil is  0.0002 mg/kg of body weight. So, an adult weighing 60 kg should take less than 0.012 mg of this insecticide daily, to avoid chronic toxicity. According to Ms. Yhoshida Lakshani, gotukola and mukunuwenna had 372 ppb of fipronil residues. Thus, eating such  gotukola or Mukunuwenna  becomes risky on eating about 35 grams (7  spoons) of it without cooking or cleaning.  Washing will not remove these insecticides as they are largely water insoluble.

However,  washing and cooking are very important as vegetables in tropical countries are contaminated with amoeba, shigella, E-coli, hookworm and other organisms. They are more dangerous than small amounts of insecticide residues found in crops.

Furthermore, if vegetables are cooked with some water in an open pan (i.e., adopting the Sri Lankan method of making a ‘maelluma’ ), the pesticide  volatilizes with the steam. According to research by Xavier and collaborators ( Environmental Monitoring and Assessment Volume 186, p 5429) even sun drying, or dipping in solutions of tamarind, turmeric, vinegar and slaked lime and wet scrubbing could remove more than 90 % of fipronil residues.  Even if nothing is done, the fipronil disappears with a half life of about four  days. So, not applying the insecticide close to harvesting greatly reduces the level of fipronil contamination.

In fact, most of these pesticides are not needed for growing Mukunuwenna and Gotukola.

  1. Profenofos. This insecticide is used against MealyBugs, caterpillars, and aphids. The European MAL for this is 10 parts per billion (ppb), while the US limit is 1000 ppb, i.e., some 100 times higher. This does not mean that the substance suddenly becomes 100 times less toxic when inside the USA, but simply that different farming practices (mainly used on cotton) are used, and within those practices, one may tolerate 100 times more insecticide residues than in colder Northern Europe.

From a health point of view, the  Admissible Daily Intake  for chronic toxicity applies.  The WHO-FAO stipulates 0.03 mg per kg of body weight per day as the ADI, while china uses 1.0 mg/kg of body weight. An adult weighing  60 kg may take up to 60 mg every day.  According to a Divaina newspaper report (3-11-2018)  Ms.  Lakshani had found some 7583 ppb of this insecticide while the MAL quoted by her was 10 ppb. So, the reporter had concluded that the pesticide residues were alarmingly high and pose a health risk. Instead, if we use the Chinese ADI value of 60 mg, given a contamination level of 7583 ppb, a 60 kg man  must  eat over 79 kg of vegetable per day. If we use 0.03 mg/kg of body weight as the ADI,  it is still about 2.4  kg  of the contaminated vegetable DAILY to run a health risk!

Hence the claim that eating such vegetables pose a health risk is utter nonsense. However, the use of excess pesticide is a waste of money. Nor should we load it to the ecosystem even if the decay times are short. We should also not take to organic farming” fashionable among the elite classes, because of its negative environmental  impact.  Such farming needs more water, more land and more manual labour to obtain mere meager harvests. Manual labour (as opposed to no-tillage agriculture) strongly increases soil erosin.

The other pesticides detected, namely , Phenthoate (insecticide) and Tebuconazole (Fungicide) have admissible daily intake (ADI) amounts such that a 60 kg adult has to take 0.06 mg to 1.8 mg to reach chronic toxicity. If the gotukola or Mukunuwenna had, say 300 ppb of the pesticide, it is necessary to eat about 3 to18 kg of the vegetable DAILY for there to be a health risk from the pesticide residues. Since even a  goat wouldn’t eat such large amounts of gotukola daily, these residues pose absolutely no health risk to us.

  1. Glyphosate.

Although glyphosate  has been very much in the news, it has not figured at the Peradeniya meeting.  Instead we go to the Sri Lanka Medical Association journal (SLMA) where  a lecture by Dr. Sanath Gunatilake (SG) is reported in August 2018.  SG is a California doctor who joined with Ms. Seananayke (a Kelaniya psychic), and Dr. Jayasumana (a very recent medical graduate)  in publishing an article claiming that glyphosate together with arsenic and hard water causes kidney disease in the North central province. SG claims that the adjuvants (substances added in small amounts to glyphosate formulations) are a thousand times more toxic than glyphosate. Yet, he ignores that these same adjuvants are also found in greater amounts in common shampoos and household detergents. Field trials by Professor Acquavella showed  that the adjuvants are found in parts per trillion (truly negligible and at the limit of detection) in the blood of farmers who use the herbicide regularly.

Dr. Gunatillake too makes the mistake that the agricultural MALs  determine toxicity.  SG and the public who read the websites and newsletters of EcoWatch, Organic Consumers, Dr. Mercola, Moms across America, Whole-Food consumers, Beyond Pesticides, Detox, Food-democracy-Now, Avaaz team, Alliance for Natural Health,  etc., ignore what the MRLs imply, and talk of alarmingly dangerous levels of pesticides in food” after comparing pesticide residues with the MALs.

Contrary to what seemed to be assumed by Dr. Gunatilake, and by most members of the public including various Jurors who pronounce on glyphosate lawsuits,  we already noted that the MALs are NOT related to the health risk from the contamination, but to good agricultural practice! When Dr. SG  claims  (SLMA Journal) that Taiwan set a limit of  1 ppb of glyphosate in Oates, he should ask why America allows 30 ppm of glyphosate in the same Oates, i.e., 30,000 times more! It clearly cannot be a matter of toxicity of the glyphosate residues to human health!

According to the WHO-FAO 2016-May press release, the admissible daily intake (ADI) for glyphosate residues is 1 mg per body weight. That is, a 60 kg person can regularly ingest up to 60 mg of glyphosate daily without risk of chronic toxicity. Dr. Sanath Gunatilleke seems to think that even 10 ppb is too  unsafe, because Taiwan sets  an MAL of 1 ppb. Now, if the  Oates had 10 ppb, to reach the unsafe ADI, an adult must consume  6000 kg, or six metric tons of Oates daily! And yet, Dr. Sanath Gunatilleke had stated this Taiwanese concern about  1ppb of glyphosate in Oates, without blinking in front of the Sri Lanka Medical Association.

Sometimes MALs are mere weapons of trade wars. In Sri Lanka it has been a political weapon in the hand of the Toxin-free” lobby which ignores particulate dust,  exhaust-gas pollution, urban garbage mounds, and  many other  acute  health risks.  Sri Lanka lost over 60 billion in three years due to the ban on glyphosate, debilitated the tea farmer and destroyed the maize farmers. But Dr. Gunatilleke and others who follow him  seem to believe that that these MALs, and not the ADI that are a measure of the safety threshold. In fact, he seems to go even further.

We present below, a figure from Dr. Gunatilleke’s address published in the SLMA journal, where we have added the caption Cum Grano Salis” – that is, we are saying, take all this with a grain of salt”. Why? The data” in the blue region are  far too close to instrumental error to be trustworthy.

We have added the blue and red ellipses. The region enclosed in blue in this figure contains claims of studies at levels of glyphosate below 2ppb. In effect, results in this regime are effectively beyond standard analytical techniques, and so great care must be taken in quoting or using such data” unless they have been confirmed by several laboratories having the protocols and capacity to do analytical work with  picogram” accuracy.

Dr. SG is claiming essentially that the effect of very low doses (below few parts per billion) of glyphosate has not been tested. Taking such trace amounts in isolation, without including the effect of a multiplicity of other substances and ions is nothing but simple falsification of biochemistry.  It is no different to the claims of homeopaths about just the memory of a drug in water is enough to cure a disease, even without the drug being present”.

Dr. SG  gives several items indicating Endocrine disruption at 0.17 parts per trillion,  chronic effects of Roundup at 4 parts per trillion, Hepatorenal effects at 90 parts per trillion. These are simply an exercise in gullibility. Furthermore, claims of highly questionable individuals like Seralini (2012) are listed and presented as Peer-Reviewed” research. In fact , Seralini et al.  have a habit of publication by press release”since they had to retract their publications from peer-reviewed journals when false claims were detected (

The region in the figure enclosed in the RED ellipse involves glyphsate-herbicide toxicity claimed to be caused by the presence of adjuvants which are a 1000 times more toxic” than glyphosate.  But such adjuvants   may only be present in the blood at mere parts per trillion! If we picked one man out of the whole world population, that is 1 in seven billion. One in a trillion is one man from nearly a hundred such worlds! These are not credible quantities.

Dr. S. G. refers to the work of Mesnage et al (2013) and claims that if adjuvants are included, then the toxicity increases by 1000 fold. Is he talking of chronic toxicity or acute toxicity? Is he talking of ingestion via the gut or via the lungs? Toxicities differ in all different cases. What has been presented in Dr. SG’s figure has no connection with what happens in the field-environment. But artificial in-vitro situations can be created where only  glyphosate and adjuvants are present in a test tube at the ppb levels, together with a few victim cells. Even then the results remain inconclusive! Has Dr. SG or Dr. Mesnage tested common detergents and shampoos (containing similar adjuvants) at parts per trillion level for their toxicity” as well?

The kind of claims  by Dr Sanath Gunatilleke and his team are possible because most people are not used to thinking quantitatively. They do not understand that one part in a trillion is like finding a needle in a whole solar system of needles. And yet, public policy is dictated by such mythology.

It is  not only parts per trillion chemistry that Dr. Gunatilleke puts into his grain of salt. He also abuses basic synthetic organic chemistry and established knowledge in bond energies as well stereo-chemistry.  He repeats an unsubstantiated  claim of the computer engineer Dr. Stephanie Seneff that glyphosate can become a building block” into DNA and disrupt” the biochemistry of the body by substituting for glycine.  After all, Stephanie Seneff is also said to claim that those who purchase her life-style program can live to the age of 111 years!

[The author was the Professor of Chemistry and Vice Chancellor of Vidyodaya (now Jayawardenapura) University in the mid-1970s, and  pioneered food technology and environmental science  programs in Sri Lankan academia. He currently works in Canada, on topics related to quantum physics as well as environmental science. His most recent contribution to environmental science was on Cadmium in fertilizers, soil and food”, Environ. Geochem. Health. 2018 Jun 23. doi: 10.1007/s10653-018-0140-x.]

Leave a Reply

You must be logged in to post a comment.



Copyright © 2022 All Rights Reserved. Powered by Wordpress