Integrating human and ecotoxicological impacts into willingness to pay evaluation: transition from paraquat to atrazine use in sweet corn cultivation

Abstract

The paraquat ban has led to a shift in the use of pesticides in sweet corn cultivation, atrazine as one of the alternative pesticides. This change has led to altered human-ecological impacts that have yet to be explored. The related monetary values of farmers as reflected through their willingness to pay is unknown. This study assessed the health and freshwater ecotoxicity impacts of paraquat and atrazine in soil cultivation using the USEtox 2.12 model. The value of farmers on the impact of the change was explained by willingness to pay (WTP). The theory of planned behavior (TPB) factors, a psychological theory that links beliefs to behavior was applied to consider factors that affect willingness to pay using ordered logit model. The questionnaire surveys of sweet corn farmers in Lopburi, Saraburi and Nakhon Ratchasima Provinces were interviewed twice via telephone. The study of 41 farmers indicated that farmers had used paraquat before being banned for 0.86±0.27 kg active ingredient (a.i.)/rai/year was substituted by 0.92±0.43 kg a.i./rai/year for atrazine. Based on toxicological data, human toxicities were slightly higher on the paraquat use (1.33×10-6±4.21×10-7 disability adjusted life years (DALY)) than the atrazine use (1.30×10-6±6.21×10-7 DALY). On the other hand, the corresponding ecological toxicity were significantly lower on the paraquat use (68.37±21.7 potentially disappeared fraction of species (PDF). m3.day) than the atrazine use (1262.67±600.83 PDF.m3.day). Farmer's average willingness to pay to reduce human and ecological toxicity from the current pesticide use was 216.46±132.28 baht/year and 162.44±111.74 baht/year, respectively. The results on TPB factors affecting willingness to pay revealed that farmers with neutral subjective norms towards agricultural scholars were less likely to be willing to pay to reduce ecotoxicity impact than farmers with positive subjective norms (p≤0.05). These findings provide useful information to relevant agencies to improve the effectiveness of pesticide policies for sustainable cultivation of sweet corn.