Most of pesticides are organic and not water soluble. If it get absorb, there is a lot of chemical changes too. In such circumstances how it get accoumolated and contaminate food cycle? It is true or it is just a phobia created by researchers?
It is not phobia at all. Residual pesticide could be accumulated in the ultimate products because every pesticide has certain period for their complete degradation (half life) in the plant system itself. However, most of the commercial products are harvested and make marketing before passing the pesticide half life. This might one of the major reason to get pesticide acumulating and contaminating foods in our food cycle.
@ Nafees, Pesticides are detrimental for the environment. It may pollute air, water and soil. If you are exposed to it , you may get irritation of the nose, eyes, skin etc. It linked to a wide range of human health hazards. Most pesticides are complex organic molecules and not very heat stable. They can very well enter into the food cycle through cuticle, stomata, wounds and other plant parts.The best way to remove it by washing, peeling and cooking as it enters inside the food. It require prolong exposure to temperature well above 100 degree Celsius. Therefore, it is better stick to organic produce.
Dear Nafees - Totally agree with Ujjal! However, please note that (1) this applies to "systemic" pesticides, and (2) "half-life" is the time required for a pesticide to break down to 50% of the original amount used after a single half-life. After two half-lives, 25% of the pesticide will remain and so forth..
Best wishes - Lara
The concept of half life is understood and applicable to the pesticides present in the open environment. My question is about pesticides abosorbed/adsorbed by a plant. Let me make the question simple.
First part of the question is "plant can absorb pesticides?"
Second part is "the absorbed pesticides can remain in it's original shape?"
Yes, plants do absorb pesticides. The quantity of pesticide absorbed depends on the pesticide and how it is formulated and how it is applied. Some pesticides remain skin deep, others move further into the plant.
Ujjal's answer applies to all pesticides. The pesticide will degrade in the plant through metabolism and other routes depending on where the pesticide is in the plant.
There are many degradation paths. An initial loss of pesticide is in the application. No matter how careful, some of a foliar applied pesticide ends up on the ground where it is not effective. Upon application initial processes of hydrolysis and photolysis degrade much of the pesticide rapidly. This is one half life, but not all the pesticide stays on the surface, and some gets to the undersides of leaves where it is more protected from photolysis. For every location on/in the plant there will be a different decay rate. If you could measure the pesticide concentration at a small scale (1 cubic micron, or each microliter) you would find places where the pesticide lasts a long time and others where it is gone in a day or two. The total of all of these is the environmental fate of the pesticide.
Pesticides are a useful and critical tool in large scale agricultural production of food and fiber. A careful and informed application of pesticides will have great benefit to man with minimal environmental impact. The problem is that pesticides are often abused. A little is good, but more is not better. There have been problems with understanding what the pesticide does in the crop and environment (e.g. problems with resistance). We are still working on that, as evidenced by the large number of scientists still working on these problems. We are getting better.
In extoling the evils of pesticides people often think of natural as safe. However, many natural products are as lethal to humans as any pesticide. Cyanide is an obvious example. We even use natural products as pesticides: pyrethrum and nicotine are two examples for insecticides extracted from plants. Many natural products are "benign" only because the individual components have not been tested sufficiently. If you take something like "celery powder" and change it into a list of chemicals you would need to include cautionary statements on many of the chemicals that the plant uses to defend against herbivores. You are just another herbivore as far as the plant is concerned.
Plant uptakes pesticides and finally residual parts remain in the different plant parts including fruits/vegetables and other edible parts. The pesticide may be remain in its original form or may be changed to Metabolites depends on the biotic and abiotic factors act on it.
The toxicity depends on the degradation pattern and half life. But, sometimes metabolites become more toxic than original pesticides. E.g. Endosulfan sulfate (metabolite of Endosulfan) is more persistant and toxic than original any isomer of Endosulfan.
So, in recent research, the residual part is defined as the original pesticides and its major metabolites for its proper investigation. In such case, MS (Mass Spectrometry) analysis with LC/GC will give you the entire solution.
I don't know of any pesticide that "remains in its original form" after application, either to the plant itself or to the surrounding soil. The breakdown (degradation, metabolism, etc) occurs by both biotic and abiotic processes with a measured half-life for each process. During the registration and approval for a product, the half-lives and the products of the breakdown must be identified if they comprise 10% or more of the total material (TRR, total radioactive residues, since the studies are done using radio-labeled material). The totals present at the time of harvest are also measured, usually as the sum of the original parent product and any toxicologically significant residues. The total residues at harvest determine the residue tolerance (or MRL), the legally defined upper concentration for the sum of all residues. The MRL's are used for consumer safety assessments. The dislodgeable residues from the plant surfaces are used in spray re-entry safety assessments. The studies required are dictated by law in the countries that approve the products, for example in the US they are part of FIFRA, in the EU they are listed in EC 1007/2009. The required study designs are also specified by law and are available (for example on the OECD website) Summaries of the studies are also available (outside of NA, you can search the EFSA website). The end result from all of these studies are the application conditions and minimum pre- harvest intervals on the product labels. These conditions are legal requirements. For specific product information, I have found it useful to search for the product DAR (Data Assessment Record), often on the EFSA (European Food Safety Agency) website. I hope this helps.
As a half-life problem it will take a very long time for every last molecule of the original product to be degraded. It might be worth wondering about the biological consequence of the last remaining molecule. Also, that last molecule is well below any detection threshold of any piece of equipment currently available.
While the answer to the question is yes it is true that pesticide will adsorb/absorb into crop plants and remain (for a while) in its original form, some of the other answers to this post would suggest that the process and result is more complex.
Since the studies required to gain product approval are done using the product as applied and all subsequent degradation, the biological consequences of all forms, original molecules and all subsequent degradation products are part of the studies. For example, a 21 day mouse study considers the tox effects during that 21 days, including degradation. A 2 year study rat would do the same over a longer time. For a harvested crop, the interval between application and harvest are studied. That's why both the final residue definition and the MRL are based on the total that are "toxicologically relevant". Separate tox studies are done on degradation products. For example, half-life data on soil degradation (in several soil types) are used in combination with required confined rotational crop studies to determine plant-back intervals, that time interval between the original application and the planting of another crop. For an insecticide, the half-life data are used to design studies that determine the minimum time before the produce and be harvested, the "pre-harvest interval". The most prevalent, direct use of half-life data are in environmental modeling to predict, for example, the potential to reach ground and surface water as specified by the laws, e.g the water framework initiative in the EU.
You can hardly avoid pesticide residues in food. Even if the chemical analysis shows "zero" residues this merely proves that residues are below the Limit of Detection (LOD) of the method used. Therefore there is an established limit which should not be exceeded. This limit is represented by the MRLs (maximum residue limits). These are today fixed on the basis of Good Agricultural Practice (GAP) experimentation for residues determination in food. Based on this Pre- Harvest Intervals (PHI)for each crop/pesticide combination are being set.
Of course pesticides are being chemically (through enzymes) degraded in the plant after absorption from the plant tissue. This degradation process depends on the nature of the molecule, on the crop and the climatic conditions. Yet you should always bear in mind following three points:
1. A portion of the active ingredient very often remains intact after harvest
2. As the degradation process proceeds metabolites are produced. Some of them are toxic.
3. Some of the pesticides ( fortunately not the very new ones) do accumulate in lipid tissues,
If you really want to worry, sometimes the metabolites are more toxic than the parent compound.
true, but that toxicity is part of the safety assessment since each toxic metabolite is also tested and all of the residues included in the risk assessment. The risk assessment begins with the MRL and very general assumptions about consumption to estimate the maximum possible exposure. For example, for consumers the first assumption is that all of the food eaten has residues at the MRL to give the maximum daily dose, then that value is compared to the measured toxicity, divided by safety factors (usually 100-1000X) to give the toxicity to exposure ratio (TER). The minimum TER is set by policy, or by statute.
Yes, it's true that pesticides remain in crops and lead to pesticide residues. The level of residues can be hold below the maximum residue limit (MRL) if good agricultural practices are used.
Hi,
Pesticides can cumulative in Water, Soil and Air. Also pesticides can cumulative in plant and Effective factors in absorption and distribution of pesticides in plants include:
1-physico-Chemically properties like Solubility in water, vapor pressure, molecular weight, Kow and ........
2- Environment conditions like Temperature and water value and Organic and inorganic materials in soil.
3- plant characters as root type, form and leave chemical properties and wax value in that.
The Best Regard
S. Mahmoudvand
I recommend Dr. Samaneh Mahmoudvand for your answer"
Pesticides can cumulative in Water, Soil and Air. Also pesticides can cumulative in plant and Effective factors in absorption and distribution of pesticides in plants include:
1-physico-Chemically properties like Solubility in water, vapor pressure, molecular weight, Kow and ........
2- Environment conditions like Temperature and water value and Organic and inorganic materials in soil.
3- plant characters as root type, form and leave chemical properties and wax value in that".
Pesticides are allochthonous pollutants discharged in natural environments. Once in the environment, natural factors such as biodegradation, photodegradation and chemical hydrolysis trigger partial or total pesticide transformation and reduce their environmental persistence. However, some degraded compounds have a greater ecotoxicological effect on the biota that the parent compounds and the change in the physicochemical properties increase the bioaccumulation, toxicity and transference processes.
The best example of pesticide bioacumulation is DDT very well explained by Rachel Carson in her book The Silent Spring. DDT can't be dissolved in water; it is, however, easily dissolved in organic solvents, fats or oils. As a result of its tendency to dissolve in fats, DDT can build up in the fatty tissues of animals that are exposed to it. This accumulated build-up is known as bioaccumulation, and DDT is described by the EPA as a persistent, bio-accumulative toxin.
This bioaccumulation often refers to the process whereby certain substances such as pesticides or heavy metals work their way into lakes, rivers and the ocean, and then move up the food chain in progressively greater concentrations as they are incorporated into the diet of aquatic organisms such as zooplankton, which in turn are eaten perhaps by fish, which then may be eaten by bigger fish, large birds, animals, or humans.
DDT is highly persistent in the environment. The soil half-life for DDT is from 2 to 15 years. The half-life of DDT in an aquatic environment is about 150 years, but the amount of chemical remaining after a half-life will always depend on the amount of the chemical originally applied.
It depends on the pesticide used ,the method of use , the concentration used, and the safety period or when to harvest the crop. I think pesticides are important in increasing the agricultural production per ca pita if used in the proper method, there will be residues but within the EPA lower tolerant level.
Please see the following:
https://www.fda.gov/food/pesticides/pesticide-residue-monitoring-program-questions-and-answers
Yes, it is true. Mechanisms of environmental contamination of pesticides are as follows:
-Misplacement and leakage during transportation, distribution or storage.
-Enters the plant or plant product by contact or systematic action, air by evaporation, water by dissolution and soil by adsorption.
-Adsorbed by various constituents of the environment and transported to other places mainly by water and air movements.
-Pick up by various biological systems, and
-Chemically/biologically transformed to other non-toxic compounds.
The Ways of Inducing Adverse Effects:
-On man and domestic animals, mostly through contaminated foods and feeds, and
-On wildlife including fish and birds by absorption/accumulation of pesticide through food.
It is always a good idea to wash the vegetables with soap and water, then rinse well before using. Most people skip these steps because it takes time. Chemicals are present on the surface as well as in crevices and bruises of the skin. In addition to pesticides, cucumbers and tomatoes are often coated with a waxy substance to give them a shine. I don't think pesticides or these surface coatings are meant to be ingested. What is the safe level? The agriculture industry will say any residues are harmless and safe. But you can make your own decision. It is your health.
Dear Nafees, I suggest you read the Book of Pesticides in soil and water edited by W.D.GUENZI . Madison,Wisconsion USA
It is not true that pesticides can accumulate inside the plant in its original form. out side the plant it may remain for a long time.
I, myself have started work on it. soon I will share my findings. our last year experiment shows that pesticides can't remain in its original form.
Thanks to all respectable contributers. It is/was w good discussion. I enjoyed each comments. Appreciated
Hi, Dr Nafees Mohammad
I follower u about this study... I smell some Agricultural products can guess pesticides type in cucumber, tomato and ..... this is very terrible.
Good Luck
The Best Regards
S.Mahmoudvand
Respected Samaneh Mahmoudvand,
That pesticides may be sprayed on the surface of vegetables. That can be removed by washing, as suggested by Dr. Srini Vasan and other researchers.
My question is about the pesticides adsorbed or absorbed.
Thanks for your interest and regards.
Tanx for ur attention
But, some of Pesticides dont removed with washing, Then part of pesticides penetrate in Plant.
What r ur opinion ?
The Best Regards
Yes, pesticides penetrate into different parts of plant through adsorption, absorption or water uptakes.
Yes, it is true that pesticides may find it's way to reach inside the plant body, fruit and grain. But it can't remain there for a long time in it's original shape. Plant work on it and decomposed it. Therefore, in case of plants the world "accoumolation" is not applicable.
In human and other animals the use of "bio accumulation" and "bio magnification" is justified.
Used in the years 60-70. XX century pesticides DDT, which was later withdrawn from agricultural use, as it later turned out to cause serious diseases and diseases in humans. These pesticides, used in large quantities on cultivated fields in the Northern Hemisphere, were quickly found in the bodies of penguins in Antaktyd in an unchanged form.
I think DDT is no more available in the market due to international ban on it's manufacturing in early 1970s. It is true that big amount was available for quite some time. After about 50 years period, I don't think it is available in such quantity to be used in agriculture. Similarly, somany other chlorinated pesticides and pesticides having bioaccumulation ability have been banned. Therefore, such pesticides are beyond the scope of this question. In the present scenario, there are pesticides that has the ability to be accumulated in animals bodies. But the question is about bio-accumulation in different parts of a plant.
Yes Chnar Fathulla, your point is noted. Thanks for your contribution.
Yes, it affect on the chemistry of soil and it due to soil contamination
Plants have no capacity to accumulate pesticides. Because when pesticides give entry in plant body, it start degrading it. Pesticides accumulated and dried on the surface of fruit or vegetables is not coming under the definition of bio- accumulation.
Plant can't accumulate pesticides. There is no such system under which pesticides, after entering into plant body get accumulated.
For human being it is true, it accumulate fat soluble pesticides.
When we study cell biology, no such mechanism exists in plants in which they can accumulate pesticides in its original form. The plant cell will try to degrade pesticides. If the cell fail to do so, it will die. If the cell die, the absorbed/ adsorbed pesticides can't because part of food chain.
Dear Nafees.
i think what Logan A. Norris wrote i useful in answering your important question.
please see attach file (behavior of pesticides in plants, Logan A. Norris)
Best Regard
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