Arsenic Standards and Guidelines

Arsenic in Pesticides

Pesticide are being marketed and sold by the form of pesticide formulations. It is a combination of chemical compounds. These chemical compounds may present in the formulations as Active ingredient / s, Inert ingredient / s and Impurities. If Arsenic is present in pesticide formulations in Sri Lanka, it should be belong to one of these three components mentioned. Let’s see the different scenarios separately.

Arsenic as an active ingredient

Active ingredient is the main component of the pesticide formulations. This component mainly consists of one chemical compound and rarely two or more chemical compounds. Often they are organic chemicals, but inorganic compounds too can be found. This is the main compound that directly target the pest concerned therefore named as “Active”. Glyphosates, Carbofuran and Chloropyrifos are some of the commonly used active ingredients in Sri Lanka. In the past, Arsenic was registered and used as an active ingredient in pesticide formulations. These Arsenic contained compounds included Calcium arsenate, Copper arsenate, Lead arsenate, Copper aceto arsenite, Disodium methane arsenate (DSMA) and Monosodium methane arsenate (MSMA). These compounds were banned as they were likely to cause serious health hazardous to human beings and animals in the environment. Sri Lanka was not an exemption as above mentioned Arsenic contained pesticides were banned with accordance to revised pesticide act 2001. Therefore it is obvious that Arsenic as an active ingredient can not be present in pesticides marketed in Sri Lanka. If arsenic present as an active ingredient it is then direct violation of the rules and regulations improvised through the pesticide act in Sri Lanka.

Arsenic as an inert ingredient

Any substance that is present in pesticide formulations other than “active” ingredient and intentionally added is called an inert ingredient. He word “inert” it self is vague. It is important to note that “inert” does not imply that chemical is non-toxic. Usually these inert compounds are not directly link with destroying the pest and therefore from that perspective these are considered as inert compounds. But they may have their own physiochemical and biological activity. This claim can be proven very simply as >500 inert compounds that is being used as inert ingredients have also listed and registered as active ingredients. These inert compounds play a key role in increasing effectiveness of the pesticide formulation. The current list of approved inert ingredients for food use pesticide products is listed in electronic code of federal registrations (e-CFR) USA. If we carefully analysis this list we can see that Arsenic or Arsenic related compounds can not be used as inert ingredients in pesticides.

The definition of the “inert ingredients” clearly states that these compounds are intentionally added. Therefore we can argue that Pesticide manufactures do know all the inert ingredients that they added through out the manufacturing process of pesticides. When certain pesticide registered, it is mandatory to provide a list of all the ingredients (active, inert and any other chemicals present) to the ROP Sri Lanka. ROP Sri Lanka has the prime access to that information and may be used in the registration and other decision making processes. If Arsenic present as an inert ingredient in Pesticides marketed it should be already declared at the ROP Sri Lanka. In case of a legal case we should be able to get the declarations and decide whether reported Arsenic can be present or not. In my opinion, Arsenic can no be included as an inert ingredient in accordance with e-CFR USA list. We must also remember that Arsenic compounds are already banned as an active ingredient because they are non-threshold carcinogenic substances and therefore can not be present even as an inert ingredient in a certain pesticide.

Arsenic as an impurity

Impurities in pesticide formulations may be reported as a starting material, formed during synthesis and storage and handling. It has been reported that certain pesticides may contain Arsenic as an impurity. With reference to IUPAC report published in 2003 some active ingredients such as Aluminum Phosphide (0.04g As / kg), Copper Oxychloride (50 mg As/ kg), DSMA (27g As/kg for pentavalent and 2.2g As/kg for trivalent), MSMA (27g As/kg for pentavalent and 2.2g As/kg for trivalent), Zinc Phosphide (0.04g As /kg) and Zineb (200mg As/ kg) may contain Arsenic and limited to maximum allowable concentrations mentioned above. If we carefully analysis the list above we can see that both DSMA and MSMA are banned in Sri Lanka mainly due o the revised pesticide act 2001. The only pesticide active ingredient that contains Arsenic as an impurity is the Copper Oxychloride which may have >10 different formulations in Sri Lanka. Therefore if Arsenic present as an impurity in certain pesticides it should be formulations of Copper Oxychlorides not in glyphosates or carbofuran.

It should be noted that compounds like Glyphosate technical, Glyphosate technical concentrate, Glyphosate Isopropylamine salt concentrates, Glysophate soluble concentrates and Glyphosate water soluble granules may used as starting materials in the manufacturing process of glyphosate formulations. According to the published FAO specifications and evaluations for plant protection products , above mentioned compounds may only contain Formaldehyde( maximum 1.3g/kg), N-nitrosoglyphosate (1mg/kg) and insoluble in 1M NaOH as impurities. IUPAC technical report published in 2003 titled “Significance of impurities in he safety evaluation of crop protection products” listed impurities identified or likely to be present in pesticides. According to that glyphosate pesticides may only contain N- methylyglyphosate (28g/kg), aminomethylphosphonic acid (17g/kg), hydroxometheylphosponic acid (12g/kg), (phosphonomethylimino di(aciic acid) (10g/kg) and N-nitrosoglyphosate (1mg/kg). So both reports indicate that Arsenic or Arsenic related compounds can not be present in glyphosate formulations even as an impurity unless it is intentionally added.

By carefully analyzing above three scenarios, it can be concluded that Arsenic or Arsenic related compounds can not be present in pesticide formulations in Sri Lanka unless the manufacturers are intentionally added these compounds in the manufacturing process of pesticides. There is a very small probability that Arsenic and Arsenic contained compounds are accidentally added to the pesticides. If we carefully analysis the follow up role and recent activities of the pesticide importers in Sri Lanka this fact is rather negligible. The truth has been revealed only to some extent and it is the correct time to go beyond the reality.

Dr. P.Mangala C.S. De Silva
Senior Lecturer
Department of Zoology
University of Ruhuna