Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
allow the estimation of even trace amounts of pesticides in any commodity. However, in these
chromatographic analysis estimation of pesticide residues is done on comparison basis with that of
technical standards.
Pesticides, being toxic in nature, are supposed to be thoroughly screened for their safety,
using different animal models. For this purpose, studies on acute toxicity, chronic toxicity,
allergenicity etc., are undertaken. These data are evaluated and the No-Observed-Adverse-Effect
Level (NOAEL) is calculated from the chronic toxicity studies. In case of toxic pesticides, acute
reference dose is also taken into consideration. This NOAEL and Acute Reference Dose are
supposed to be taken as the starting information for prescribing the tolerance limits of pesticides in
food commodities. NOAEL is usually referred to in terms of milligrams of that particular pesticide
per kilogram of body weight.
From this NOAEL, the Acceptable Daily Intake (ADI) is calculated which is expressed in terms of
mg/kg body weight and is an indication of the fact that if a human being consumes that amount of
pesticide everyday, throughout his lifetime, it will not cause appreciable health risk. On the basis
of this MRL is a dynamic concept which is determined and is also renewed from time to time.
Maximum Residue Limit (MRL) is the maximum concentration of a pesticide residue resulting from
the use of a pesticide according to Good Agricultural Practice (GAP). It is the limit that is legally
permitted or recognized as acceptable in or on a food, agricultural commodity, or animal food. The
concentration is expressed in milligrams of pesticide residue per kilogram of the commodity. Under
the PFA Act, MRL or Tolerance Limits (TLs) are fixed considering MRLs recommended by Codex
or based on supervised trials conducted in India as well as the dietary habits of our population.
Decontamination of pesticide residues from vegetables
The decontamination of pesticide residues from vegetables is an extremely important step
to be followed in view of the extreme doses of pesticides which are being used on vegetables,
especially the ones which are consumed raw. The different methods which can be employed for
decontamination of pesticides are
Washing: Household washing procedures are normally carried out with running or standing water
at moderate temperatures. Chlorine or ozone can also be passed into wash water to improve
effectiveness of washing. The effects depend upon the physicochemical properties of pesticides
such as water solubility, hydrolytic rate constant, volatility and octanol – water partition coefficient.
Washing process leads to reduction of hydrophilic pesticide residues on the surface of the
vegetables. The temperature of washing water also has an influence on the reduction of residue
level from vegetables as hot washing leads to higher reduction in pesticide residues than cold
water. Washing coupled with gentle rubbing under tap water dislodges pesticide residues
significantly.
Peeling: The outer leaves of vegetables often contain residues of applied pesticide during crop
growth. There are several examples depicting the presence of high pesticide residue
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