Pesticides and cancer risks in agriculture

Neurotoxicology of dopamine: Victim or assailant?

Since the identification of dopamine as a neurotransmitter in the mid-20th century, investigators have examined the regulation of dopamine homeostasis at a basic biological level and in human disorders. Genetic animal models that manipulate the expression of proteins involved in dopamine homeostasis have provided key insight into the consequences of dysregulated dopamine. As a result, we have come to understand the potential of dopamine to act as an endogenous neurotoxin through the generation of reactive oxygen species and reactive metabolites that can damage cellular macromolecules. Endogenous factors, such as genetic variation and subcellular processes, and exogenous factors, such as environmental exposures, have been identified as contributors to the dysregulation of dopamine homeostasis. Given the variety of dysregulating factors that impact dopamine homeostasis and the potential for dopamine itself to contribute to further cellular dysfunction, dopamine can be viewed as both the victim and an assailant of neurotoxicity. Parkinson's disease has emerged as the exemplar case study of dopamine dysregulation due to the genetic and environmental factors known to contribute to disease risk, and due to the evidence of dysregulated dopamine as a pathologic and pathogenic feature of the disease. This review, inspired by the talk, "Dopamine in Durham: location, location, location" presented by Dr. Miller for the Jacob Hooisma Memorial Lecture at the International Neurotoxicology Association meeting in 2023, offers a primer on dopamine toxicity covering endogenous and exogenous factors that disrupt dopamine homeostasis and the actions of dopamine as an endogenous neurotoxin.

Adverse health effects of pesticides in agrarian populations of developing countries

Developing countries use only 20% of the world's agrochemicals, yet they suffer 99% of deaths from pesticide poisoning. Pesticide poisoning is a significant problem in developing countries primarily because of unsafe pesticide application and handling practices. Safety is further exacerbated by the illiteracy and poverty that prevails in most farming communities of developing countries. Pesticides classified as being extremely or highly hazardous by FAO and WHO, including those banned by other countries, continue to be used in developing countries. Many farmers in developing countries continue to be exposed to pesticides from either storing them in or near their residences, or from inadequate or unsafe application or handling practices. Farming populations exposed to pesticides suffer from several health problems, primarily neurological abnormalities, respiratory ailments, and reproductive, endocrinological, and dermal problems. In developing countries, the scientific literature (including the Indian Institute of Toxicology Research, India) have taken the initiative to monitor health problems resulting from pesticide exposure in agrarian communities. The welfare fund for agricultural laborers could institute a special program for pesticide applicators in developing countries. The primary need, currently, in such countries is creation and implementation of sound national policies to effectively articulate appropriate guidelines for managing farm pest control activities. Such policies should be aimed at both limiting pesticide exposure and usage, but doing so without damaging the yields of food production. If such steps are taken, it is fully expected that the incidence of adverse health consequences for agrarian populations from pesticide toxicity will decrease, and the health of farmers improve.

Case-control study of lung cancer among sugar cane farmers in India

OBJECTIVES

To investigate the risk of lung cancer among sugar cane farmers and sugar mill workers.

METHODS

A case-control study was conducted based in six hospitals in the predominantly sugar cane farming districts of the province of Maharashtra in India. Newly diagnosed, histologically confirmed cases were identified from these hospitals between May 1996 and April 1998. Other cancers were chosen as controls and matched to cases by age, sex, district of residence, and timing of diagnosis.

RESULTS

Adjusting for confounders, an increased risk of lung cancer was found for workers ever employed on a sugar cane farm (odds ratio (OR) 1.92, 95% confidence interval (95% CI) 1.08 to 3.40). Increased risks were found for work involving preparation of the farm (OR 1.81, 95% CI 0.99 to 3.27) and burning of the farm after harvesting (OR 1.82, 95% CI 0.99 to 3.34). Non-significant increases in risks were found for harvesting the crop (OR 1.41, 95% CI 0.70 to 2.90) and processing the cane in the mills (OR 1.70, 95% CI 0.20 to 12.60).

CONCLUSIONS

Exposure to fibres of biogenic amorphous silica (BAS) formed from silica absorbed from the soil and deposited in the leaves of the sugar cane crop or crystalline silica formed as a result of conversion of BAS to cristobalite at high temperatures may account for the increased risks of lung cancer among sugar cane farmers.