Insecticides pose threats to the global non-target environment due to their high toxicities and widespread agricultural applications. Surface waters currently face a severe biodiversity crisis, and some are at risk due to insecticide exposure. A recent study published by Stehle and Schulz (2015) compiled the current scientific knowledge on insecticide exposure of global surface waters, considering more than 50 compounds important for global agriculture and all major insecticide classes (i.e., organochlorines, organophosphates/carbamates, pyrethroids, and neonicotinoids). This study evaluated more than 200,000 database entries and retrieved 11,300 measured insecticide concentrations (MICs) for 28 of the >50 insecticide compounds considered. A total of 838 scientific studies published between 1962 and 2012 were reviewed. The contribution of articles (n = 54) published (1971–2012) during the 50 year history in the Bulletin of Environmental Contamination and Toxicology (BECT) represented 6.4 % of the total (see Supplemental Materials for all 54 BECT publications).
A temporal analysis of these BECT articles (Fig. 1) shows that, although the first BECT article reporting an insecticide surface water concentration appeared in 1971, the vast majority (n = 47) of BECT studies with monitoring data were published in the last 20 years; in addition, only 18 studies were published before the year 2000, whereas 36 studies were published from 2000 onward (Fig. 1). This progressive increase in number of BECT publications focusing on the research theme “environmental contamination” in the last 15–20 years was also shown in a recent BECT editorial by Drouillard and Benett (2015). Concerning the geographical scope, BECT articles reported insecticide surface water exposure data worldwide, with a main focus on Asia (n = 296 concentrations), North America (n = 185 concentrations), and Africa (n = 173 concentrations); however, insecticide environmental contamination data were also published for South America (n = 64 concentrations), Europe (n = 55 concentrations) and Australia (n = 29 concentrations). This summary of geographical distribution of reports illustrates the international nature of BECT publications.
A more in-depth analysis of BECT´s contribution to the global surface water insecticide exposure dataset evaluated in Stehle and Schulz (2015) showed that the field concentrations reported in the 54 BECT publications comprised 18 different insecticide compounds and 802 MICs; overall, 52.2 % (n = 419 cases) of these 802 concentrations exceeded their regulatory threshold levels (RTL), which nearly exactly match the 52.4 % RTL exceedance rate reported for the 11,300 concentrations evaluated in the larger study by Stehle and Schulz (2015).
An analysis of the contribution of the different insecticide classes to the insecticide exposure dataset showed that 251 concentrations of organochlorine insecticides, 409 organophosphorous/carbamates, 80 pyrethroids, and 62 neonicotinoid concentrations were reported in BECT articles. However, two points are noteworthy. First, the study by Stehle and Schulz (2015) considered only one organochlorine insecticide (i.e., endosulfan), as this is the only organochlorine insecticide currently in use; many more surface water concentrations were published in BECT for other well-studied organochlorine insecticides but are not included in this analysis. Second, despite the comprehensive literature review that was conducted, Stehle and Schulz (2015) were able to retrieve only 131 neonicotinoid surface water concentrations. Remarkably, approximately 50 % (i.e., 62 concentrations) of those were published in BECT. This indicates that BECT is an important scientific resource for topical information on the environmental contamination of current pesticides of concern [see, e.g., Sánchez-Bayo (2014) for environmental concerns related to global agricultural neonicotinoid use].
In the last four decades, an overall shift of focus concerning environmental concentrations measured and subsequently reported for the different insecticide classes can be observed in BECT articles (Fig. 2). Organochlorine insecticides (i.e., endosulfan) were predominately measured and reported from 1970 until the mid 1990s, with rare publication of organochlorine surface water concentrations detected in the aquatic environment after the year 2000. At the beginning of the 1990s, surface water concentrations of organophosphorous and carbamate insecticides gained prominence in BECT articles and have subsequently been reported quite frequently in the last 20 years. After the year 2000, pyrethroid concentrations came to the fore; however, for reasons unknown, no pyrethroid surface water concentrations sampled after the year 2005 were reported in BECT articles. Most recently (2012), BECT articles were published on neonicotinoid surface water concentrations. Overall, the temporal evolution of insecticide concentrations measured in surface waters globally, and reported in BECT, reflect the market introduction and use pattern of insecticides in global agriculture. BECT has thus provided important and up-to-date scientific information on the environmental risks of the respective insecticide compounds over the past 50 years.
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Sánchez-Bayo F (2014) The trouble with neonicotinoids. Science 346(6211):806–807
Stehle S, Schulz R (2015) Agricultural insecticides threaten surface waters at the global scale. Proc Natl Acad Sci USA 112(18):5750–5755
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Stehle, S., Schulz, R. Global Insecticide Surface Water Contamination Assessment: BECT’s Contribution in the Last Five Decades. Bull Environ Contam Toxicol 96, 563–564 (2016). https://doi.org/10.1007/s00128-016-1788-5