A.Kader Jackaria,C.Chem,FRSC. Former Director Forensic Science Laboratory

“When you can measure what you are speaking about, and express it in numbers,you know something about it;but when you cannot measure it,when you cannot express it in numbers,your knowledge is of a meagre and unsatisfactory kind.” (Lord Kelvin)

Historical

Man has always been concerned with the control of pests,especially in his endeavour to increase agricultural productivity. The first pesticides were of natural origin.Nicotine from tobacco, has been used since the eighteenth century and pyrethrum,a well-known insecticide,was used in Persia even before that time. Many synthetic inorganic preparations such as arsenates and  thiocyanates were later introduced as insecticides.

The discovery of the insecticidal properties of DDT (dichlorodiphenyltrichloroethane) in 1939 was a turning point in the history of pest control.DDT is a most effective weapon against typhus and the other insect-borne disease,malaria.Since the discovery of DDT there has been a dramatic rise in the number of commercially available synthetic organic pesticides.In the forties a whole group of other ‘organochlorinated’ compounds were produced and marketed under the tradenames of chlordane,lindane,heptachlor,aldrin,endrin and dieldrin.
Then followed the emergence of the so-called ‘organophosphorous ‘ pesticides commercially available under the names of  parathion malathion, rogor and diazinon. Other pesticides belonging to different chemical groups ensued in following years to mention the Carbamates e.g.methomyl( lannate) , paraquat(Gramoxone) and Glyphosate(Round-up).

USE

Pesticides(a general term for insecticide,herbicide, fungicide and acaricide) have proved useful to agriculture and are used worldwide on a large scale to improve and increase production of a number of crops e.g. cereals, fruits and vegetables. Mauritius is no exception.

The Residue Problem

This ‘ pesticide explosion’ has brought with it a number of problems which have given cause for concern at  international level. Since 1965,Rachel Carson in her then controversial book ‘Silent Spring’ presented a strong case against the indiscriminate use of pesticides and pointed out the  dangers caused to the well-being of mankind and to his environment in general.The  metaphorical title of the book,which later became a bestseller, stems from the fact that with the destructive use of pesticides there will be an ‘absence of birdsong’.The main areas of concern have been the nature,persistence and tolerable levels of pesticide deposits  or residues in foodstuffs,vegetables,fruits,animal feedstuffs,dairy products,waters and soil. It is interesting to note that,although at first she met with fierce opposition from the chemical industries,yet she persevered. There was later  a nationwide ban on DDT in agriculture whilst  she also inspired an environmental movement that led to the creation of the U.S. Environmental Protection Agency. Most countries now have their own Ministry of  Environment.Thus, with the pesticide residue problem, some control measures both at national and international levels were  required.The Food and Agricultural Organisation(FAO) and the World Health Organisation (WHO)have been very active in tackling many aspects of the pesticide problem since they assumed international leadership in 1959.

In Mauritius the first legislative measures with respect to pesticide use were taken in 1970 and embodied in the Pesticides Control Act. Accordingly,a Pesticide Control Board was set up and, in my opinion, was functioning well and served its purpose  for many years,taking care of the manufacture, import and sale of pesticides, as well as advising on safety and precautions of use such as labelling, handling ,use of personal protective equipment ,avoidance of over-exposure and disposal.  Agricultural workers were screened at regular intervals by the Ministry of Health for the level of the enzyme cholinesterase in blood to ensure they were not over-exposed to organophosphorus  or  carbamate  pesticides which affect the nervous system. However, the residue problem was not  fully tackled.

The Control of Pesticides is now under the umbrella of The Dangerous Chemicals Control Act. (Act No, 16 0f 2004) which covers most of the aspects of the previous Pesticides Control Act  1970.

The Present Situation

 Awareness of the possible presence of  excess  pesticide residues in our fruits and  vegetables led newspaper L’Express to order a  survey towards the end of2015. Random samples were collected from  different places and submitted for analysis to the local  QuantiLab/Merieux Nutrisciences  Laboratory.  The results were astounding for pesticide residues in the samples. In brief,20% of samples analysed had residues of pesticides above the Maximum Residual Limit imposed by the European Commission on Pesticides.A Maximum Residue Level (MRL),commonly expressed in milligram(mg) /kilogram or ppm(parts per million) is the highest level of a pesticide that is legally tolerated in or on food or feed when pesticides are applied correctly. The amount of residues in food must be safe for the consumer and  must be as low as possible.(See L’express dimanche  17 janvier 2016 for full details and  Tables of Results). This must have been an eye-opener  if not  sounding the alarm bell.It  has certainly triggered the preparation of The Use of Pesticides Bill in the National Assembly this year.

I read with keen interest the article and comments of Mr Philippe A. Forget in L’express of lundi 11 Juin 2018. He welcomed the Bill  but drew attention to some important lacunae.

I will limit myself to  comments on his apprehension as to the number of molecules listed and the instrumentation used.

The list of Pesticides in the First Schedule of the Bill  is clearly  not exhaustive  but the  legislation therefore should  not have  overlooked  any pesticide that has been or could  be encountered . A proviso should have been included in the Bill.

There is also the problem of banned pesticides that can still be brought illegally in the country or the contamination of the  soil as some pesticides are quite stable and can persist for up to 20 years.  Possible mislabelling of pesticide formulations must also be considered i.e. the product inside the container does not correspond to the name  on the label. Only chemical analysis can tell.

As to  frequent consumption of fruits and vegetables containing residue levels of pesticides above the MRL, the adverse and ill-effects cannot be under-estimated due to  what is known as the cumulative effect over a period of time.Also, their now well-known  potential as ‘Perturbateurs endocriniens’ (disturbance to our hormonal system) and carcinogenic nature.The toxicology of pesticides is now well documented.

The Use of Pesticides Bill(No. V1 of 2018)

This new bill ,voted in the National Assembly in July 2018 ,with its main objectives  described below, is a separate piece of legislation but not totally independent of the Dangerous Chemicals Control Act(2004).It takes care of previous aspects related to pesticide use but this time with more emphasis on the residue problem and with acceptable risk reduction  to human health and the environment.

The main object of this Bill is clearly explained at the outset:  “to regulate and monitor the importation and use of pesticides in or on certain fresh fruits,plants,seeds or vegetables with a view to,inter alia,minimising risks to human health and the environment.”

This is no doubt a laudable initiative and a step in the right direction to tackle this thorny problem of pesticide contamination in the food chain and the environment.The Public Health issue is, above all, of paramount importance.This piece of legislation will complement to a large extent specific and  important aspects not under the purview of The Dangerous Chemicals Control Act.

During the debate in the National Assembly  both sides of the House commended the Bill overall  whilst some members had reservations on a few issues. Some wanted to limit the number of pesticides imported especially those that have been banned in other countries. This is ,in a way, an approach to risk reduction. Subsequently, there have been  some more articles in the Press  commenting again on some important aspects that have been missed out.For instance,we can refer to the interesting article from our compatriot in the United States, Rattan Gujadhur , entitled “Brief reflections on the new Use of Pesticides Bill:Is it a missed opportunity?” and the other one by Mr Amarjeet Beegoo:” Le Use of Pesticides Bill  a des lacunes.”

As a professional chemist , conversant with  pesticide analysis, and also as a consumer,I am  concerned about the chemical analytical aspects and health issues.

The chemical industries  have produced thousands of  substances beneficial to mankind but which at the same time are harmful if not well managed. Such is the situation with pesticides and there is need to both accrue the benefits and draw the line above which they can be harmful  to human health.

Thanks to major development in instrumentation coupled with computer technology we have nowadays  highly sophisticated pieces of equipment that meet our analytical requirements in terms of both specificity and sensitivity. To put it in simple terms, you can confirm both the identity of a chemical substance and measure its quantity to a very low level e.g. in not only micrograms  but in some instances in nanograms and picograms.( 1ug =10^-6g,

1ng=10^-9g and 1pg=10^-12g)

The selection of appropriate equipment,as detailed below,(they are expensive and the choice is vital) when set up and programmed for targeted substances and beyond  will do the tasks  marvellously in terms of type( the two instruments covering  800 or more pesticide molecules) and quantity present. And, of course, you have to keep up and add new substances to the built-in library as they appear on the market.

In addition, Pesticide Laboratories must have a collection of all  pure ingredients as Certified Reference Materials obtained from reliable sources.

Two different types of instruments are ‘de facto’ required to cover all the pesticides under consideration:

1)GC/MS-MS( Gas Chromatograph  coupled/interfaced with Mass Spectrometer) for the analysis of volatile organic pesticides(e.g. organochloro and organophosphorus  and pyrethrins) and

(2)LC/MS-MS (Liquid Chromatograph coupled/interfaced with Mass Spectrometer) for the analysis of non-volatile, water soluble pesticides).

Each instrument comes with its own software enabling detection, identification and quantitation.

You will agree  that once you have these two vital pieces of very expensive equipment,that’s not job done! All staff of the laboratory concerned must have specialised knowledge and training and ,above all, real experience to be able to deliver the goods.There is ,from my personal experience,also a good deal of work setting-up the instruments ready for operation and initially running many tests and trials. Having surmounted all the major obstacles the tasks might be routine in the long run. So also said the late Professor Christiaan Barnard  after practising open- heart surgery for many years ! Pesticide analysis can be complex in that you are dealing with different  biological matrices(plants, fruits, vegetables) and you have to get rid of interfering substances such as  fats, chlorophyll and other plant pigments

Analytical methods that will satisfy Laboratory Accreditation by certified bodies( e.g.UKAS,SANAS or MAURITAS) must be used. There are other stringent criteria stated to meet all the requirements for accreditation. A laboratory can be accredited for selected methods of analysis at one time and not necessarily for all methods at the same time. However, sound management principles must also prevail.

Accreditation is the hallmark of competence, adherence to recognised analytical practice and good organisation.This is why I would have thought “accredited laboratory” rather than” designated laboratory” should have appeared  in The Use of Pesticides Bill to avoid any vagueness or confusion.

Pending having full analytical capabilities coupled with accreditation status to cover the gamut of  residual pesticides especially in samples of fruits and vegetable by the Food Technology of the Ministry of Agriculture,as has been reported, one would initially  in the short term have to resort to any  local accredited laboratory of the private sector  to avoid any more delay in the interest of Public Health.

MISUSE/ABUSE

Both misuse and abuse of pesticides  in normal circumstances can occur through ignorance or zealousness. Excessive or aggressive use without the recommended precautionary measures can lead to over-exposure and constitute a serious health hazard. There is also probably an abuse in the different number or cocktails of pesticides used. The new Bill envisages to educate and train  plant growers and agricultural workers as to the judicious use of pesticides.

As Forensic Toxicologist at the Forensic Science Laboratory I have over the years analysed thousands of post-mortem specimens of stomach contents and blood which had revealed the presence of pesticides and which accounted for the cause of death. Police Exhibits comprising containers of pesticides were also analysed and with positive results. These were mainly cases of suicide or accidental poisoning and rarely malicious poisoning by a third party.Pesticides account for more than 80-90 per cent of yearly  poisoning cases. Ready accessibility and their known reputation as killers are the most likely reasons.

CONCLUDING REMARKS

It is to be deplored that most of the constructive and valuable suggestions proposed from both within and outside the National Assembly  have been ignored. It is never too late to mend and let us hope relevant amendments might still be possible in the very  near future.

Finally any Act of Parliament to be able to achieve its objectives  depends entirely on its full implementation and enforcement.

References

(1) A.K.Jackaria (1974) University of Strathclyde M.Sc. Thesis: The Application of Gas Liquid Chromatography to the Analysis of some Pesticides

(2)  Wikipedia: On Rachel Carson

(3) PESTICIDES:  Que Donnons-nous a manger a nos enfants? L’Express dimanche  17 Janvier 2016

 (4) Philippe A. Forget : The Use of Pesticides Bill: Certainement mieux que rien! Mais encore…?  L’Express 11 Juin 2018

(5) The  European Commission Website on Pesticides

(6) The Use of Pesticides Bill (N0. V1 of 2018) 18 May 2018

(7) Rattan Gujadhur: Brief Reflections on the new Use of Pesticides Bill: Is it an opportunity missed? L’Express 4 juillet 2018

(8) Amarjeet Beegoo: Le Use of Pesticides Bill a des lacunes LExpress 9 Juillet  2018

(9) Qu’en est-il des produits agricoles importes? Week-End dimanche 8 Juillet 2018

(10) Use of Pesticides Act : Mise en oeuvre dans la controverse: Le Defi 25 Juillet 2018