Hart, L. G., Larson, E. H., & Lishner, D. M.; “Rural definitions for health policy and research;” American Journal of Public Health, 2005, 95(7), 1149-1155; DOI: 10.2105/AJPH.2004.042432.
The term “rural” suggests many things to many people, such as agricultural landscapes, isolation, small towns, and low population density. However, defining “rural” for health policy and research purposes requires researchers and policy analysts to specify which aspects of rurality are most relevant to the topic at hand and then select an appropriate definition. Rural and urban taxonomies often do not discuss important demographic, cultural, and economic differences across rural places-differences that have major implications for policy and research. Factors such as geographic scale and region also must be considered. Several useful rural taxonomies are discussed and compared in this article. Careful attention to the definition of “rural” is required for effectively targeting policy and research aimed at improving the health of rural Americans. FULL TEXT
Jugulam, Mithila, Varanasi, Aruna K., Varanasi, Vijaya K., & Prasad, P. V. V. (2018). Climate Change Influence on Herbicide Efficacy and Weed Management. In S. S. Yadav, R. J. Redden, J. L. Hatfield, A. W. Ebert, & D. Hunter (Eds.), Food Security and Climate Change (First ed., pp. 433-448): John Wiley & Sons Ltd.
Climate change refers to a change in the climate system that persists for long periods of time, irrespective of the cause. Since the industrial revolution, climate change has been more often associated with a rise in the concentration of greenhouse gases such as carbon dioxide (CO2), methane, nitrous oxide, and halocarbons. The concentration of atmospheric CO2 is steadily rising and is expected to reach ∼1000 μmolmol−1 by the year 2100 with a simultaneous increase of 2–4∘C in the earth’s annual surface temperature (IPCC, 2013). Human activities such as the burning of fossil fuels and deforestation have contributed to a large extent to the emission of greenhouse gases (IPCC 2013, MacCracken et al., 1990). Continued emission of these gases may lead to unprecedented climate changes involving high global temperatures, erratic precipitation and wind patterns, and weather extremities such as droughts, floods, and severe storms (Tubiello et al., 2007; Robinson and Gross, 2010; Gillett et al., 2011; Coumou and Rahmstorf, 2012). Such extreme weather events and rapid climatic changes will have major impacts on the stability of ecosystems; consequently influencing plant life and agriculture (Dukes and Mooney, 1999). Crop production and agronomic practices involving weed management and pest control may be severely affected by these altered abiotic conditions primarily caused by changes in climate and climate variability (Dukes et al., 2009, Singer et al., 2013). Warmer and wetter climates not only affect weed growth but also change chemical properties of certain herbicides; thereby altering their performance on weeds and their control (Poorter and Navas, 2003; Dukes et al., 2009). Determining the response of weeds and herbicides to increased CO2 levels and associated changes in other climate variables is critical to optimize weed management strategies in the context of climate change. This chapter provides an overview of the impacts of climate change factors on weed growth and herbicide efficacy, particularly focusing on the impacts of climate factors on the underlying physiological mechanisms that determine herbicide performance. FULL TEXT
Shealy, Dana B., Bonin, Michael A., Wooten, Joe V., Ashley, David L., Needham, Larry L., & Bond, Andrew E.; “Application of an improved method for the analysis of pesticides and their metabolites in the urine of farmer applicators and their families;” Environment International, 1996, 22(6), 661-675; DOI: 10.1016/s0160-4120(96)00058-x.
As the annual use of pesticides in the United States has escalated, public health agencies have become increasingly concerned about chronic pesticide exposure. However, without reliable, accurate analytical methods for biological monitoring, low-level chronic exposures are often difficult to assess. A method for measuring simultaneously the urinary residues of as many as 20 pesticides has been significantly improved. The method uses a sample preparation which includes enzyme digestion, extraction, and chemical derivatization of the analytes. The derivatized analytes are measured by using gas chromatography coupled with isotope-dilution tandem mass spectrometry. The limits of detection of the modified method are in the high pg/L – low μg/L range, and the average coefficient of variation (CV) of the method was below 20% for most analytes, with approximately 100% accuracy in quantification. This method was used to measure the internal doses of pesticides among selected farmer applicators and their families. Definite exposure and elimination patterns (i.e., an increase in urinary analyte levels following application and then a gradual decrease to background levels) were observed among the farmer applicators and many of the family members whose crops were treated with carbaryl, dicamba, and 2,4-D esters and amines. Although the spouses of farm workers sometimes exhibited the same elimination pattern, the levels of the targeted pesticides or metabolites found in their urine were not outside the ranges found in the general U.S. population (reference range). The farmer applicators who applied the pesticides and some of their children appeared to have higher pesticide or metabolite levels in their urine than those found in the general U.S. population, but their levels were generally comparable to or lower than reported levels in other occupationally exposed individuals. These results, however, were obtained from a nonrandom sampling of farm residents specifically targeted to particular exposures who may have altered their practices because they were being observed; therefore, further study is required to determine if these results are representative of pesticide levels among residents on all farms where these pesticides are applied using the same application techniques. Using this method to measure exposure in a small nonrandom farm population allowed differentiation between overt and background exposure. In addition, the important role of reference-range information in distinguishing between various levels of environmental exposure was reaffirmed. FULL TEXT
Harris, S. A., Villeneuve, P. J., Crawley, C. D., Mays, J. E., Yeary, R. A., Hurto, K. A., & Meeker, J. D.; “National study of exposure to pesticides among professional applicators: an investigation based on urinary biomarkers;” Journal of Agricultural and Food Chemistry, 2010, 58(18), 10253-10261; DOI: 10.1021/jf101209g.
Epidemiologic studies of pesticides have been subject to important biases arising from exposure misclassification. Although turf applicators are exposed to a variety of pesticides, these exposures have not been well characterized. This paper describes a repeated measures study of 135 TruGreen applicators over three spraying seasons via the collection of 1028 urine samples. These applicators were employed in six cities across the United States. Twenty-four-hour estimates (mug) were calculated for the parent compounds 2,4-D, MCPA, mecoprop, dicamba, and imidacloprid and for the insecticide metabolites MPA and 6-CNA. Descriptive statistics were used to characterize the urinary levels of these pesticides, whereas mixed models were applied to describe the variance apportionment with respect to city, season, individual, and day of sampling. The contributions to the overall variance explained by each of these factors varied considerably by the type of pesticide. The implications for characterizing exposures in these workers within the context of a cohort study are discussed. FULL TEXT
Delcour, Ilse, Spanoghe, Pieter, & Uyttendaele, Mieke; “Literature review: Impact of climate change on pesticide use;” Food Research International, 2015, 68, 7-15; DOI: 10.1016/j.foodres.2014.09.030.
Agricultural yields strongly depend on crop protection measures. The main purpose of pesticide use is to increase food security, with a secondary goal being increased standard of living. In view of a changing climate, not only crop yields but also pesticide use is expected to be affected. Therefore, an analysis of the detailed effect of changing climatic variables on pesticide use is conducted. Not only effects on cultivated crops, occurring pests and pesticide efficiency are considered but also implications for technological development, regulations and the economic situation are included as all of these aspects can influence pesticide use. The objective of this review is to gain insights into the specific effect of climate change on the consumer exposure caused by pesticide residues on crops. In terms of climate change, temperature increase and changes in precipitation patterns are the main pest and pathogen infection determinants. An increased pesticide use is expected in form of higher amounts, doses, frequencies and different varieties or types of products applied. Climate change will reduce environmental concentrations of pesticides due to a combination of increased volatilization and accelerated degradation, both strongly affected by a high moisture content, elevated temperatures and direct exposure to sunlight. Pesticide dissipation seems also to be benefitted by higher amounts of precipitation. To overcome this, pesticide use might be changed. An adapted pesticide use will finally impact consumer exposure at the end of the food chain. FULL TEXT
Choudhury, P. P., & Saha, S.; “Dynamics of pesticides under changing climatic scenario;” Environmental Monitoring and Assessment, 2021, 192(Suppl 1), 814; DOI: 10.1007/s10661-020-08719-y.
Ziska, Lewis H.; “Climate Change and the Herbicide Paradigm: Visiting the Future;” Agronomy, 2020, 10(12); DOI: 10.3390/agronomy10121953.
Weeds are recognized globally as a major constraint to crop production and food security. In recent decades, that constraint has been minimized through the extensive use of herbicides in conjunction with genetically modified resistant crops. However, as is becoming evident, such a stratagem is resulting in evolutionary selection for widespread herbicide resistance and the need for a reformation of current practices regarding weed management. Whereas such a need is recognized within the traditional auspices of weed science, it is also imperative to include emerging evidence that rising levels of carbon dioxide (CO2) and climatic shifts will impose additional selection pressures that will, in turn, affect herbicide efficacy. The goal of the current perspective is to provide historical context of herbicide use, outline the biological basis for CO2/climate impacts on weed biology, and address the need to integrate this information to provide a long-term sustainable paradigm for weed management. FULL TEXT
Vilà, Montserrat, Beaury, Evelyn M., Blumenthal, Dana M., Bradley, Bethany A., Early, Regan, Laginhas, Brittany B., Trillo, Alejandro, Dukes, Jeffrey S., Sorte, Cascade J. B., & Ibáñez, Inés; “Understanding the combined impacts of weeds and climate change on crops;” Environmental Research Letters, 2021, 16(3); DOI: 10.1088/1748-9326/abe14b.
Crops worldwide are simultaneously affected by weeds, which reduce yield, and by climate change, which can negatively or positively affect both crop and weed species. While the individual effects of environmental change and of weeds on crop yield have been assessed, the combined effects have not been broadly characterized. To explore the simultaneous impacts of weeds with changes in climate-related environmental conditions on future food production, we conducted a meta-analysis of 171 observations measuring the individual and combined effects of weeds and elevated CO2, drought or warming on 23 crop species. The combined effect of weeds and environmental change tended to be additive. On average, weeds reduced crop yield by 28%, a value that was not significantly different from the simultaneous effect of weeds and environmental change (27%), due to increased variability when acting together. The negative effect of weeds on crop yield was mitigated by elevated CO2 and warming, but added to the negative effect of drought. The impact of weeds with environmental change was also dependent on the photosynthetic pathway of the weed/crop pair and on crop identity. Native and non-native weeds had similarly negative effects on yield, with or without environmental change. Weed impact with environmental change was also independent of whether the crop was infested with a single or multiple weed species. Since weed impacts remain negative under environmental change, our results highlight the need to evaluate the efficacy of different weed management practices under climate change. Understanding that the effects of environmental change and weeds are, on average, additive brings us closer to developing useful forecasts of future crop performance. FULL TEXT
Schulz, R., Bub, S., Petschick, L. L., Stehle, S., & Wolfram, J.; “Applied pesticide toxicity shifts toward plants and invertebrates, even in GM crops;” Science, 2021, 372(6537), 81-84; DOI: 10.1126/science.abe1148.
Pesticide impacts are usually discussed in the context of applied amounts while disregarding the large but environmentally relevant variations in substance-specific toxicity. Here, we systemically interpret changes in the use of 381 pesticides over 25 years by considering 1591 substance-specific acute toxicity threshold values for eight nontarget species groups. We find that the toxicity of applied insecticides to aquatic invertebrates and pollinators has increased considerably—in sharp contrast to the applied amount—and that this increase has been driven by highly toxic pyrethroids and neonicotinoids, respectively. We also report increasing applied toxicity to aquatic invertebrates and pollinators in genetically modified (GM) corn and to terrestrial plants in herbicide-tolerant soybeans since approximately 2010. Our results challenge the claims of a decrease in the environmental impacts of pesticide use. FULL TEXT
Nolan, R. J., Rick, D. L., Freshour, N. L., & Saunders, J. H.; “Chlorpyrifos: Pharmacokinetics in human volunteers;” Toxicology and Applied Pharmacology, 1984, 73(1), 8-15; DOI: 10.1016/0041-008x(84)90046-2.
The kinetics of chlorpyrifos, an organophosphorothioate insecticide, and its principal metabolite, 3,5,6-trichloro-2-pyridinol (3,5,6-TCP), were investigated in six healthy male volunteers given a single 0.5 mg/kg po and, 2 or more weeks later, a 0.5 or 5.0 mg/kg dermal dose of chlorpyrifos. No signs or symptoms of toxicity or changes in erythrocyte cholinesterase were observed. Plasma cholinesterase was depressed to 15% of predose levels by the 0.5 mg/kg po dose but was essentially unchanged following the 5.0 mg/kg dermal dose. Blood chlorpyrifos concentrations were extremely low (less than 30 ng/ml), and no unchanged chlorpyrifos was found in the urine following either route of administration. Mean blood 3,5,6-TCP concentrations peaked at 0.93 micrograms/ml 6 hr after ingestion of the oral dose and at 0.063 micrograms/ml 24 hr after the 5.0 mg/kg dermal dose. 3,5,6-TCP was cleared from the blood and eliminated in the urine with a half-life of 27 hr following both the po and dermal doses. An average of 70% of the po dose but less than 3% of the dermal dose was excreted in the urine as 3,5,6-TCP; thus only a small fraction of the dermally applied chlorpyrifos was absorbed. Chlorpyrifos and its principal metabolite were rapidly eliminated and therefore have a low potential to accumulate in man on repeated exposures. Based on these data, blood and/or urinary 3,5,6-TCP concentrations could be used to quantify the amount of chlorpyrifos absorbed under actual use conditions.