Transformation and ecotoxicity of carbamic pesticides in water.
BACKGROUND
N-methylcarbamate insecticides are widely used chemicals for crop protection. This study examines the hydrolytic and photolytic cleavage of benfuracarb, carbosulfan and carbofuran under natural conditions. Their toxicity and that of the corresponding main degradation products toward aquatic organisms were evaluated.


METHODS
Suspensions of benfuracarb, carbosulfan and carbofuran in water were exposed to sunlight, with one set of dark controls, for 6 days, and analyzed by 1H-NMR and HPLC. Acute toxicity tests were performed on Brachionus calyciflorus, Daphnia magna, and Thamnocefalus platyurus. Chronic tests were performed on Pseudokirchneriella subcapitata, and Ceriodaphnia dubia.


CONCLUSIONS
Under sunlight irradiation, benfuracarb and carbosulfan gave off carbofuran and carbofuran-phenol, while only carbofuran was detected in the dark experiments. The latter was degraded to phenol by exposure to sunlight. Effects of pH, humic acid and KNO3 were evaluated by kinetics on dilute solutions in the dark and by UV irradiation, which evidenced the lability of the pesticide at pH 9. All three pesticides and phenol exhibited acute and higher chronic toxicity towards the aquatic organisms tested.


CONCLUSIONS
Investigation on the hydrolysis and photolysis of benfuracarb and carbosulfan under natural conditions provides evidence concerning the selective decay to carbofuran and/or phenol. Carbofuran is found to be more persistent and toxic.


CONCLUSIONS
The decay of benfuracarb and carbosulfan to carbofuran and the relative stability of this latter pesticide account for many papers that report the detection of carbofuran in water, fruits and vegetables.
Iesce
Maria Rosaria
MR
Dipartimento Chimica Organica e Biochimica, Università Federico II di Napoli, Via Cinthia 4, 80126 Napoli, Italy. iesce@unina.it
della Greca
Marina
M
Cermolal
Flavio
F
Rubino
Maria
M
Isidori
Marina
M
Pascarella
Luigia
L
D000818:Animals; D001572:Benzofurans / Q000378:metabolism / Q000633:toxicity*; D002219:Carbamates / Q000378:metabolism / Q000633:toxicity*; D002235:Carbofuran / Q000378:metabolism / Q000633:toxicity*; D003621:Daphnia; D007306:Insecticides / Q000378:metabolism / Q000633:toxicity*; D007928:Lethal Dose 50; D012403:Rotifera; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity
D001572:Benzofurans; D002219:Carbamates; D007306:Insecticides; D014874:Water Pollutants, Chemical; D015091:beta-Alanine; C096128:benfuracarb; D002235:Carbofuran; C035038:carbosulfan