Influence of the processing factors on pesticide residues in fruits and vegetables and its application in consumer risk assessment

Pesticides are widely used in food production to increase food security despite the fact that they can have negative health effects on consumers. Pesticide residues have been found in various fruits and vegetables; both raw and processed. One of the most common routes of pesticide exposure in consumers is via food consumption. Most foods are consumed after passing through various culinary and processing treatments. In this thesis the influence of the processing factors on pesticide residues in fruits and vegetables and its application in consumer risk assessment was investigated. Firstly, existing scientific literature on effects of processing on pesticide residues in fruits and vegetables was analysed using meta-analysis of response ratios. This is a possible method of combining and quantifying effects of food processing on pesticide residue levels. The method was able to indicate which processes cause reduction and which may cause both reduction and an increase in residue levels. Average reduction of residue levels was indicated by blanching, boiling, canning, frying, juicing, peeling and washing of fruits and vegetables with an average processing factor (response ratio) ranging from 0.10 to 0.82. The processing factors for baking, boiling, canning and juicing ranged from 0.24 to 2.51, indicating both reduction and increases for the 95 and 99.5% confidence intervals. Secondly, the relationship between physico-chemical properties and processing techniques was investigated. Here for a comparison of influences of the following physico-chemical properties during processing were carried out: water solubility (Sw), water-octanol partition coefficient (Kow), Henry coefficient (H) and vapour pressure (Vp). The influences of physico-chemical properties during processing were significant (P < 0.05) in the stewing and washing processes. The differences between the behaviour of leafy and non-leafy vegetables were also investigated and showed a significant difference in frying, peeling, stewing and washing but not in boiling. The distributions from the five processing methods (boiling, frying, peeling, stewing and washing) were investigated. The common distributions displayed by the samples involved during the processing methods were lognormal, generalised extreme value and weibull. Thirdly, the exposure assessment and human health impact of oncogenic potency of pesticides was performed from raw and processed fruits and vegetables consumed by the Belgian population. The oncogenic risk was calculated by multiplying the estimated daily intake (EDI) of the pesticide residue with the oncogenic potency factor (Q*) of the concerned pesticide. The estimated dietary oncogenic risk was mainly from procymidone, iprodione, vinclozolin and dithiocarbamates. The total potential oncogenic risk was calculated to be 2.76 x 10-3 before processing and 8.97 x 10-4 after processing. The risk was higher than the EPA acceptable limit of 1 x 10-6. Despite the calculated levels exceeding the EPA acceptable limit, food processing activities reduced the dietary oncogenic risk to an average of 33.8%. Fourthly, the potential risk of acetylcholinesterase (AChE) inhibiting pesticides was investigated. For this a cumulative risk assessment of organophosphates and carbamates, for the consumption of fruits and vegetables by the Belgian population, was performed. The Relative potency factor (RPF) approach was used and chlorpyrifos was chosen as index compound. The RPF values were derived using BMD10 or NOAEL for AChE inhibition, mostly in the rat brain. The exposure to AChE inhibiting pesticides at the 97.5 percentile was 33.7% of the chlorpyrifos ARfD before processing and 18.3% after processing. Parathion and methomyl were the highest contributors to the ARfD. Acute cumulative risk assessment of AChE inhibiting pesticides (organophosphates and carbamates) during the time of the study did not pose any risk to the consumers. From the whole Thesis we can conclude that food processing in most cases reduced the exposure of pesticide residues. This was evident from the meta-analysis investigation since most of the processes had average processing factors less than one. The human health impact assessment of oncogenic risk exposure and acetylcholinesterase inhibiting compounds supported the findings