A review of diazinon use, contamination in surface waters, and regulatory actions in California across water years 1992–2014

Abstract

Diazinon is an organophosphorus insecticide that has been widely used in the USA and in California resulting in contamination of surface waters. Several federal and state regulations have been implemented with the aim of reducing its impact to human health and the environment, e.g., the cancellation of residential use products by the USEPA and dormant spray regulations by the California Department of Pesticide Regulation. This study reviewed the change in diazinon use and surface water contamination in accordance with the regulatory actions implemented in California over water years 1992-2014. We observed that use amounts began declining when agencies announced the intention to regulate certain use patterns and continued to decline after the implementation of those programs and regulations. The reduction in use amounts led to a downward trend in concentration data and exceedance frequencies in surface waters. Moreover, we concluded that diazinon concentrations in California's surface waters in recent years (i.e., water years 2012-2014) posed a de minimis risk to aquatic organisms.

The effects of combinations of limited ration and diazinon exposure on acetylcholinesterase activity, growth and reproduction in Oryzias latipes, the Japanese medaka

“…In this study, we describe a toxicity test with Japanese medaka ( Oryzias latipes ) exposed to diazinon, an acetylcholinesterase (AChE) inhibiting organophosphate pesticide. Diazinon is an organophosphate insecticide that, at one time, was extensively used in the USA, but has been the subject of increased regulatory efforts by the USEPA, reducing its application in the USA (USEPA, ; Wang, Singhasemanon, & Goh, ). Its use is still globally prevalent, where in various regions of the world, diazinon is used to control insects in food crops (Alighardashi, Jalali, Bokaei, & Asefi, ; Barrett & Jaward, ; Cong, Phuong, & Bayley, ).…”

A review of long-term pesticide monitoring studies to assess surface water quality trends

“…Kreuger and Nilsson (2001) extended their sampling to the off-season months (i.e., October to November) and observed substantial pesticide losses in 1992, suggesting that sampling is required in late fall and early winter for a more comprehensive assessment. Sampling in the off-season is especially important in regions where most rainfall events occur in the winter months (e.g., California), which can lead to a delay between the time of application and increased concentrations in surface waters ( Wang et al., 2017 ).…”

“…Seasonal stratification is common in the analyses of pesticide time-series because peak concentrations in agricultural settings typically occur seasonally within the spring and summer months when planting and pesticide application, particularly herbicides, take place (see Table 2 ). It should be noted that certain pesticides, which degrade slowly in and have a strong affinity to soils (e.g., diazinon, fipronil, pyrethroids), that are applied in regions where rain events dominate in the winter months (e.g., California) have shown to be delayed in their transport to surface waters relative to their time of application ( Budd et al., 2015 , 2020 ; Wang et al., 2017 ). This fact does not undermine the importance of evaluating seasonality in the analyses of pesticide time-series, but highlights the fact that the seasonality of pesticide application and peak surface water concentrations do not always coincide.…”

“…There can be a delay of several months between pesticide application and peak concentrations in regions where rainfall events occur with greater frequency in the winter months (e.g., California). This delay is particularly prominent for those pesticides (e.g., diazinon, fipronil, pyrethroids) that degrade slowly in and have a strong affinity to soils ( Budd et al., 2015 , 2020 ; Wang et al., 2017 ). Wang et al.…”

Water Quality Impairments Due to Aquatic Life Pesticide Toxicity: Prevention and Mitigation in California, USA

“…Prior to adoption of the regulations, the use of diazinon and chlorpyrifos in these “dormant sprays,” which typically occur during California's rainy season, had been linked to aquatic toxicity in the Sacramento and San Joaquin rivers (Kuivila and Foe 1995). Wang et al (2017) reported that these regulations—in combination with other federal and state regulatory changes for diazinon—improved water quality. Based on monitoring data from 2012 to 2014, they concluded that diazinon concentrations in California's surface waters posed a de minimis risk to aquatic organisms.…”