Yanhong Jin

Overuse or underuse? An observation of pesticide use in China.

Pesticide use has experienced a dramatic increase worldwide, especially in China, where a wide variety of pesticides are used in large amounts by farmers to control crop pests. While Chinese farmers are often criticized for pesticide overuse, this study shows the coexistence of overuse and underuse of pesticide based on the survey data of pesticide use in rice, cotton, maize, and wheat production in three provinces in China. A novel index amount approach is proposed to convert the amount of multiple pesticides used to control the same pest into an index amount of a referenced pesticide. We compare the summed index amount with the recommended dosage range of the referenced pesticide to classify whether pesticides are overused or underused. Using this new approach, the following main results were obtained. Pesticide overuse and underuse coexist after examining a total of 107 pesticides used to control up to 54 crop pests in rice, cotton, maize, and wheat production. In particular, pesticide overuse in more than half of the total cases for 9 crop pest species is detected. In contrast, pesticide underuse accounts for more than 20% of the total cases for 11 pests. We further indicate that the lack of knowledge and information on pesticide use and pest control among Chinese farmers may cause the coexistence of pesticide overuse and underuse. Our analysis provides indirect evidence that the commercialized agricultural extension system in China probably contributes to the coexistence of overuse and underuse. To improve pesticide use, it is urgent to reestablish the monitoring and forecasting system regarding pest control in China.

Long- and Short-Term Health Effects of Pesticide Exposure: A Cohort Study from China

Pesticides are extensively used by farmers in China. However, the effects of pesticides on farmers’ health have not yet been systematically studied. This study evaluated the effects of pesticides exposure on hematological and neurological indicators over 3 years and 10 days respectively. A cohort of 246 farmers was randomly selected from 3 provinces (Guangdong, Jiangxi, and Hebei) in China. Two rounds of health investigations, including blood tests and neurological examinations, were conducted by medical doctors before and after the crop season in 2012. The data on pesticide use in 2009–2011 were collected retrospectively via face-to-face interviews and the 2012 data were collected from personal records maintained by participants prospectively. Ordinary least square (OLS), Probit, and fixed effect models were used to evaluate the relationship between pesticides exposure frequency and the health indicators. Long-term pesticide exposure was found to be associated with increased abnormality of nerve conductions, especially in sensory nerves. It also affected a wide spectrum of health indicators based on blood tests and decreased the tibial nerve compound muscle action potential amplitudes. Short-term health effects included alterations in complete blood count, hepatic and renal functions, and nerve conduction velocities and amplitudes. However, these effects could not be detected after 3 days following pesticide exposure. Overall, our results demonstrate that pesticide exposure adversely affects blood cells, the liver, and the peripheral nervous system. Future studies are needed to elucidate the specific effects of each pesticide and the mechanisms of these effects.

Choosing Brands: Fresh Produce versus Other Products

Assuming that brands contribute to quality risk reduction, prestige, and design, we derive and test hypothesis on the willingness to pay (WTP) for brands across different product categories (electronics, clothing, packaged food, and fresh produce). Using the random effect tobit model on the stated point value of WTP and the ordered probit model on the stated range of WTP, we find that WTP for brands of fresh produce is least among the four product categories controlling for relevant demographic variations. Simulations show that fresh produce has a higher optimal price premium for brands but with a much smaller market share. Copyright 2008, Oxford University Press.

Overweight Misperception among Adolescents in the United States.

The purpose of this study was to examine the discrepancies between perceived and reported overweight status among U.S. adolescents (n>70,000), and to identify factors contributing to such discrepancies. We used the YRBSS data (years 2001-2009) and found statistically significant, gender and race specific discrepancies between perceived and reported overweight status. Factors such as BMI, school performance, and being sexually active are additional predictors of overweight misperception. The findings suggest that evidence based strategies should be employed to help adolescents establish correct weight perception. These strategies should also be tailored based on gender, race, and weight perception of target audience.

Do Neighborhood Parks and Playgrounds Reduce Childhood Obesity

Promoting physical activity in children is an important front battling Childhood obesity. This paper investigates if and by how much neighborhood parks and playgrounds, one of the most important activity-enhancing neighborhood facilities, affect childhood obesity. We employ a covariate matching technique to analyze the 2007 National Survey of Children Health data. We find that neighborhood parks and playgrounds make children more fit. The reduction in body mass index (BMI) as well as the overweight or obesity risk is both statistically and economically significant. We also find that the park impact depends on gender, age, race, income, neighborhood safety, and other neighborhood amenities. The results suggest that a provision of neighborhood parks and playgrounds is likely to make children more fit, but relevant interventions need to take socioeconomic status of the targeted children population as well as other neighborhood amenities into consideration.

The Effects of Weight Perception on Adolescents' Weight-Loss Intentions and Behaviors: Evidence from the Youth Risk Behavior Surveillance Survey.

The objective of this study was to examine the correlation between self-perception of being overweight and weight loss intentions, eating and exercise behaviors, as well as extreme weight-loss strategies for U.S. adolescents. This study uses 50,241 observations from the Youth Risk Behavior Surveillance Survey (YRBSS) 2001–2009, which were nationally representative sample of 9th- through 12th-grade students in both public and private schools in the US. This study finds that, irrespective of the weight status base on self-reported weight and height, adolescents who perceive themselves as overweight have a stronger intention to lose weight, but do not develop better eating and exercise habits, compared with their counterparts of same gender and reported weight status. Normal-weight adolescents, if they perceive themselves as overweight, are more likely to engage in health-compromising weight-loss methods. This study shows that it is critical to transform weight-loss intentions into actual behaviors among overweight/obese adolescents and improve the efficacy of behavioral interventions against childhood obesity. It also highlights the need of establishing a correct perception of body weight among normal weight adolescents to curb extreme weight-loss methods.

Factors influencing career location preferences of international graduate students in the United States

Using primary survey data, factors influencing preferences of international graduate students in the United States as to whether they prefer to stay in the United States or go back to their home country to start their careers are examined employing discrete choice analysis. Career opportunities and social climate are critical factors. Students prefer to start their careers in the country where they have more and better career opportunities, receive higher salaries, and have increased civil liberties. Differences between students who are sure and those who are not sure as to where they prefer to start their career are noted.

Agricultural Trade, Development and Toxic Risk

Abstract This paper uses a large database of laboratory test results to investigate the sources of international variation in pesticide residues on food products. We specify and estimate a model that incorporates contamination effects attributable to product pest sensitivity, pesticide toxicity levels and characteristics of the producing country. Among the latter, our model tests for the effects of income, education and openness to trade. We find large and highly significant “generic” differences in contamination of food products, reflecting pesticide applications that vary with pest sensitivity. Controlling for these differences, we find strong effects for income and education. Pesticide residues on agricultural products fall sharply as income increases, but rise significantly with education. Our model attributes the latter effect to the choice of more capital-, skill- and pesticide-intensive technologies in better-educated societies. We find no significant impact for openness to trade. Our results suggest that workers and consumers in low-income societies have far higher exposure to toxic pesticides than their counterparts in high-income societies, but that consumers in the latter experience significant increases in toxic exposure risk as agricultural trade with developing countries expands. The paper concludes with a discussion of appropriate instruments for resolving a potentially serious trade-environment conflict on this front.

Neurological effects of pesticide use among farmers in China

The intensive use of pesticides has attracted great attention from the Chinese government. However, current regulations have had limited influence on their safe use. Although the acute neurologic effects of pesticides have been well documented, little is known about their cumulative effects. Knowledge of the impact of pesticides on health may convince farmers to minimize their use. We conducted a cross-sectional study in three provinces of China to evaluate the relationship between pesticide exposure and neurological dysfunction. Crop farmers were divided into two groups depending on their level of pesticide exposure. A total of 236 participants were assessed by questionnaire and neurological examination for symptoms and signs of neuropathy. Characteristics of neurologic dysfunction following cumulative low-level exposure were assessed with logistic regression analysis. Farmers exposed to high-level pesticide use had greater risk of developing sensations of numbness or prickling (odds ratio (OR) 2.62, 95% confidence interval (CI): 1.08–6.36). After adjusting for recent exposure, the risk of numbness or prickling symptoms (OR 2.55, 95% CI: 1.04–6.25) remained statistically significant. Loss of muscle strength and decreased deep tendon reflexes had OR > 2, however, this did not reach statistical significance. These findings suggest that overuse of pesticides increased risk of neurologic dysfunction among farmers, with somatosensory small fibers most likely affected. Measures that are more efficient should be taken to curb excessive use of pesticides.

Economic analysis of job-related attributes in undergraduate students’ initial job selection

Economic tradeoffs students place on location, salary, distances to natural resource amenities, size of the city where the job is located, and commuting times for their first college graduate job are estimated using a mixed logit model for a sample of Texas A&M University students. The Midwest is the least preferred area having a mean salary premium of