Threshold Levels for Effects of Insecticides in Freshwater Ecosystems: A Review

Abstract

Abstract. A literature review of freshwater (model) ecosystem studies with neurotoxic insecticides was performed to assess ecological threshold levels, to compare these levels with the first tier approach within European Union (EU) administration procedures, and to evaluate the ecological consequences of exceeding these thresholds. Studies published between 1980 and 2001 were reviewed. Most studies covered organophosphates and synthetic pyrethroids in lentic waters. The most sensitive taxa were representatives of crustaceans, insects and fish. Based on toxic units, threshold values were equivalent for compounds with a similar mode of action. This also accounted for the nature and magnitude of direct effects at higher concentrations. Although laboratory single species toxicity tests may not allow predictions on precise ecological effects, some generalisations on effects and recovery can be made with respect to acute standard laboratory EC 50 data. The NOEC ecosystem usually is a factor of 10 or more higher than first tier acceptable concentrations, particularly in the case of single applications and acetylcholinesterase inhibitors. Acceptable concentrations, as set by the EU first tier approach, appear to be protective. Recovery of sensitive endpoints usually occurs within 2 months of the (last) application when peak concentrations remain lower than (0.1-1) · EC 50 of the most sensitive standard test species. The consistency of response patterns found in model ecosystem studies can be useful when estimating the ecological risks of pesticides. The use of an effect classification system was also helpful in evaluating effects.

Risks to Aquatic Organisms from Use of Chlorpyrifos in the United States

“…Early cosm studies of CPY were reviewed by Leeuwangh ( 1994 ), Barron and Woodburn ( 1995 ), and Giesy et al ( 1999 ). Since the publication of the Giesy et al review, results of several cosm studies of CPY have featured prominently in comparisons of cosm studies, single-species laboratory toxicity tests, and regulatory benchmarks across classes of insecticides (Brock et al 2000(Brock et al , 2006Maltby et al 2005 ;van Wijngaarden et al 2005b ). Several newer cosm studies have broadened the scope of conclusions about chlorpyrifos effects on aquatic communities to a wider range of locations and environmental conditions (Daam et al 2008a , b ;López-Mancisidor et al 2008a , b ;van Wijngaarden et al 2005a ;Zafar et al 2011 ).…”

Effects of the pyrethroid insecticide gamma-cyhalothrin on aquatic invertebrates in laboratory and outdoor microcosm tests

“…Therefore, the concerns associated with potential enantioselectivity when assessing the aquatic risk of pyrethroids, as raised by Ali et al (2003) and Liu et al (2005), are not manifested in the case of LCH when compared to the fate and effects of its active enantiomer. Besides the information for the cyhalothrins, a considerable amount of data is available from model ecosystem studies with other synthetic pyrethroids performed under various experimental conditions (see review Van Wijngaarden et al 2005). To place the GCH model ecosystem data into context with these other studies we expressed exposure concentrations as Toxic Units (TU) (Van Wijngaarden et al 2005) and corresponding observed effects were assigned to one of the effect classes (Table 6).…”

“…Besides the information for the cyhalothrins, a considerable amount of data is available from model ecosystem studies with other synthetic pyrethroids performed under various experimental conditions (see review Van Wijngaarden et al 2005). To place the GCH model ecosystem data into context with these other studies we expressed exposure concentrations as Toxic Units (TU) (Van Wijngaarden et al 2005) and corresponding observed effects were assigned to one of the effect classes (Table 6). To be in line with the other pyrethroids, where TU was based on the most sensitive standard species (either Daphnia or a fish), TU for GCH was based on the geometric mean 96 h LC 50 for Lepomis macrochirus (47.2 ng/l; Marino and Rick 2001a, b).…”

“…However, for other pyrethroids it has been reported that some insect and macrocrustacean species are significantly more sensitive than Daphnia (Maltby et al 2005;Van Wijngaarden et al 2005), and a priori it is reasonable to assume that this will also be the case for GCH. Therefore, the initial phase of the present investigation of GCH focused on determining the toxicity profile of GCH for a selection of freshwater invertebrates known to be sensitive to pyrethroids.…”

Impact of single and repeated applications of the insecticide chlorpyrifos on tropical freshwater plankton communities

“…Microcosms and mesocosms have frequently been used for the environmental risk assessment of several chemicals, like insecticides (see Maltby et al 2005 andVan Wijngaarden et al 2005 for reviews). These test systems provide more ecological realism as compared to laboratory bioassays since they include ecological processes like interactions between plankton populations while still allowing an experimental set-up.…”