Profenofos in freshwater and marine water

​Toxicant default guideline values for protecting aquatic ecosystems

October 2000

Description of chemical

Organophosphorus pesticides (OPs) are derivatives of phosphoric, phosphonic, phosphorothioic, or phosphonothioic acids, comprising many chemicals with a wide range of uses (WHO 1986). They exert their acute effects in insects, fish, birds and mammals by inhibiting the acetylcholinesterase (AChE) enzyme, but may also have a direct toxic effect (WHO 1986).

Profenofos (CAS 41198-08-7) is a phosphorothioate OP pesticide developed by Ciba-Geigy AG. It has a non-systemic action against insects and mites including ovicidal action, and has contact and stomach action (Tomlin 1994). Its IUPAC name is O-4-bromo-2-chlorophenyl O-ethyl-S-propyl phosphorothioate, formula is C₁₁H₁₅BrClO₃PS and molecular weight is 373.6. Profenofos is soluble in water only to 28 mg/L at 25°C and its log K_ow is 4.44.

Uses and environmental fate

Profenofos is an important chemical in the management strategy for insect pest resistance for the cotton industry in eastern Australia, and is used in the third stage of the strategy, usually in February to March (Shaw 1995). A maximum of three profenofos sprays per season is recommended (Shaw 1995).

The degradation rate of profenofos in water reduces with increased pH (Tomlin 1994): from 93 days at pH 5; 14.6 days at pH 7; and only 5.7 hours (0.25 d) at pH 9. Although the waters in the cotton growing areas tend to be alkaline (pH 7.5 to 8.5), Kumar (1995) detected elevated profenofos levels (up to 1.2 µg/L) in lagoons and slow flowing creeks in the cotton growing areas of New South Wales in May 1994, 6 weeks after spraying had ceased. However, other creeks and lagoons contained no residues. Residues in sediment were higher (11 to 130 µg/kg). These were generally associated with elevated residues in fish and depressed AChE activity (Kumar 1995). The half-life in soil is around 1 week (Tomlin 1994).

Aquatic toxicology

Profenofos inhibits AChE enzyme in organics and the oxon metabolite is more toxic. There are few dose-responses data reported in the literature. Tomlin (1994) reported 96-hour LC50 figures for rainbow trout (80 µg/L), crucian carp (90 µg/L) and bluegills (300 µg/L).

Freshwater fish: six species, 48 to 96-hour LC50, 19 to 2500 µg/L, Lepomis macrochirus, O. mykiss and Lebistes reticulatus were most sensitive (although an outlying figure of 2390 µg/L was reported for L. reticulatus). Anguilla japonica and Melanotaenia duboulayi were least sensitive.

Freshwater crustaceans: two species, 48 to 96-hour LC50, 0.002 µg/L (C. dubia) to 0.08 µg/L (Paratya australiensis) tentative data (not peer reviewe

d).

Freshwater algae: one species, 72-hour EC50 2900 µg/L. NOEC for growth was 1090 µg/L.

Marine crustaceans: two species, 96-hour LC50, 2.4 to 4.6 µg/L.

Australian and New Zealand data

Juvenile Australian eastern rainbowfish seem about an order of magnitude less sensitive to profenofos than overseas trout and carp (Kumar & Chapman 1998). Abdullah et al. (1994) reported that the exposure of the shrimp P. australiensis to 0.15 µg/L profenofos for 21 days caused 60% AChE depression, and repeat pulse exposures to 0.1 µg/L at 8-day intervals caused cumulated AChE depression with slow recovery. Kumar and Chapman (1997) reported a 48-h EC50 to the Australian C. dubia of 2 ng/L (0.002 µg/L) and a NOEC for reproduction (10 days) and survival (2 days) of 0.08 ng/L (0.00008 µg/L). Early life stages of fish were also very sensitive to profenofos but these data require peer reviewing before their use in guideline derivation. The 96-hour LC50 for the shrimp Paratya australiensis was 80 ng/L (0.08 µg/L). However, the 72-hour EC50 (growth) for the alga, Selenastrum capricornutum, was 2,900,000 µg/L (Stauber et al. 1996a) indicating only low toxicity to algae.

Guideline

The tentative Australian C. dubia data was not used to calculate a trigger value.

References

Abdullah AR, Kumar A & Chapman JC 1994. Inhibition of acetylcholinesterase in the Australian freshwater shrimp (Paratya australiensis) by profenofos. Environmental Toxicology and Chemistry 13, 1861-1866.

ANZECC & ARMCANZ 2000. Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand, Canberra.

Kumar A 1995. Ecotoxicology of the organophosphate pesticide, profenofos, to selected Australian fauna. PhD thesis, Macquarie University, Sydney.

Kumar A & Chapman JC 1997. A toxicity dataset for developing water quality guidelines for profenofos, an organophosphorus pesticide. Abstract in Proceedings of the Australian Society for Ecotoxicology, 4th Annual Conference, Brisbane, July 1997.

Kumar A & Chapman JC 1998. Profenofos toxicity to the eastern rainbow fish (Melanotaenia duboulayi). Environmental Toxicology and Chemistry 17, 1799–1806.
Shaw AJ 1995. Cotton pesticides guide 1994–95. New South Wales Agriculture, Australian Cotton Research Institute, Myall Vale, NSW.

Stauber JL, Adam M & Low N 1996a. Toxicity of pesticides to the freshwater alga Selenastrum capricornutum. CSIRO Investigation Report for Centre for Ecotoxicology, CSIRO, Menai, NSW.

Tomlin C 1994. The pesticide manual: A world compendium. 10th edn, British Crop Protection Council & Royal Society of Chemistry, Bath, UK.

WHO 1986. Environmental health criteria 63. Organophosphorus insecticides: A general introduction. World Health Organization, Geneva.