Pesticide Residues in Aquatic Invertebrates - Pesticides: Evaluation of Environmental Pollution - page 328

11.2.3.4 Effect of Pyrethroid on Arthropods
Synthetic pyrethroids are the most commonly used pesticides for controlling insects
because of their low toxicity to mammals (Friberg-Jensen et al. 2003). However, many
studies have shown that cypermethrin, a synthetic pyrethroid used in crop protection,
is extremely toxic to aquatic invertebrates and may cause a reduction in feeding activity,
survival, and reproduction (Day and Kaushik 1987a,b; Kjølholt et al. 1991).
Flies in the class, Insecta, including mosquitoes, blackflies, and chironomids had an
LC 50 less than 1 μg/L when exposed to pyrethroids (Anderson 1989). The 24-h LC 50 of
cypermethrin, cis- cypermethrin , deltamethrin, permethrin and its cis isomer, and fenval-
erate for Culex larvae ranged from 0.02-7 μg/L (Mulla et al. 1978). Aquatic insects includ-
ing the black fly Simulium vittatum , caddisfly Hydropsyche and Cheumatopsyche spp., mayfly
Family Heptageniidae, damselfly Enallagma and Ischnura spp., and water scavenger bee-
tle Hydrophilus spp. were exposed to three synthetic pyrethroids including permethrin,
cypermethrin, and bifenthrin. The 24-h LC 50 of this experiment presented that the syn-
thetic pyrethroid was highly toxic to aquatic insects. Bifenthrin is highly toxic to both
mayfly and damselfly (Siegfried 1993).
Pyrethroids have been scrutinized to determine their effects on organisms in the
subphylum Crustacea. Many reports have shown that pyrethroid pesticides are highly
toxic to fish and aquatic invertebrates (Christensen et al. 2005; Clark et al. 1989; Hill
1989). The toxicity of pyrethroids is due to the chemical impact on the sodium chan-
nels in the nervous system. Exposure to pyrethroids can produce sublethal effects on
aquatic invertebrates. Feeding rate and swimming ability of aquatic invertebrates are
also impacted after exposure (Christensen et al. 2005). Crustacean zooplankton are
important organisms in the aquatic ecosystem. They aid in the regeneration of nutri-
ents from primary organic matter and are an important component in the food web
(Valiela 1991 in Barnes and Mann 1991). Synthetic pyrethroids can directly and indi-
rectly affect crustacean zooplankton. They directly affect the crustacean zooplank-
ton by reducing the grazer control of phytoplankton, protozoans, and rotifers, which
results in an altered biomass and species composition in the food web. An indirect
effect can occur through impacting the other trophic levels in the aquatic food web
(Friberg-Jensen et al. 2003).
Cypermethrin is a popular synthetic pyrethroid used to control mosquitoes. In toxicity
testing, Daphnia magna was treated with cypermethrin at concentrations of 0.05, 0.1, 0.2,
0.3, 0.6, and 1.0 μg/L. The results show that 0.1 μg/L of cypermethrin reduced the content
of chlorophyll pigment, affected swimming ability, and increased mortality of D. magna
(Christensen et al. 2005). Additionally, Friberg-Jensen et al. (2003) found that Daphnia spe-
cies rapidly decreased by more than 10% in three treatments (0.47, 1.70, and 6.10 μg/L) in
contrast to the control.
Red swamp crayfish Cyprinus carpio was used to monitor the acute toxicity of three
synthetic pyrethroids: cypermethrin, deltamethrin, and cyfluthrin. The results found
that C. carpio was highly sensitive to all three pyrethroids. The 24-h LC 50 of cyperme-
thrin, deltamethrin, and cyfluthrin was 0.14, 0.17, and 0.22 μg/L, respectively (Morolli
et al. 2006).
Lambda-cyhalothrin, which is a synthetic pyrethroid, is highly toxic to aquatic inverte-
brates. For example, Caridina laevis is very sensitive to lambda-cyhalothrin. Sucahyo et al.
(2008) found the concentrations for 24-h LC 50 and 96-h LC 50 to be 0.87 μg/L and 0.33 μg/L,
respectively. Similarly, Wang et al. (2007) reported that the 96-h LC 50 for lambda-cyhalothrin
on Macrobrachium nipponense was 0.04 μg/L. The 48-h LC 50 for lambda-cyhalothrin on Daphnia