Review on hotspots, challenges, and the future of river management strategies in China

Aim: The study aimed to understand the status of pesticide residues in lactating mother’s milk, identify factors involved in the transfer of pesticide residues and health risk to infants.Methodology: A total of 153 lactating mothers were selected from four agro-climatic zones varying from subtropics to dry temperate high hills for residue analysis. The extraction and cleanup were performed by QuEChERS method. Residue were analysed by Shimadzu 2010 GC equipped with a 63Ni ECD and confirmed by Shimadzu QP 2010 Plus GC-MS through selected ion monitoring (SIM) mode. The EDI was compared with the ADI of Σ-DDT (0.02 mg kg-1 body wt d-1) established by FAO/WHO for neonate risk assessment from different pesticides. Results: The mean DDT levels in breast milk were 0.240 mg kg-1 fat (0.011 mg kg-1 milk), 0.171 mg kg-1 fat (0.010 mg kg-1 milk), 0.026 mg kg-1 fat (0.001 mg kg-1 milk) and below detectable limit (BDL) in Zones I (subtropical), II (sub-humid foothills), III (wet temperate high hills) and IV (dry temperate high hills), respectively. The residue levels decreased with an increase in parity and increased with the age or weight of the mothers. The Σ-DDT residues were higher in rural women (0.011 mg kg-1 milk) than urban (0.005 mg kg-1 milk), housewives (0.009 mg kg-1 milk) than working women (0.007 mg kg-1 milk) and lacto-vegetarians (0.007 mg kg-1 milk) than omnivorous mothers (0.005 mg kg-1 milk). The estimated daily exposure of neonates to Σ-DDT was considerably lower (0.001 mg kg-1 body weight) than the ADI (0.02 mg kg-1 body weight) indicating no appreciable risk to one-month-old infants. Interpretation: Mother's rural habitation, demography and primiparous parity seem to be the major cause for transfer of pesticide residues. The study also advocates a constant bio-monitoring of lactating mothers’ milk for pesticide residues owing to the continuous changes in the pesticide usage pattern.

Field evaluation of bednets impregnated with deltamethrin for malaria control.

Trials were undertaken in a hypoendemic area of malaria in an area bordering Vietnam, in Napo County of Guangxi Zhuang Autonomous Region, China. The aim was to compare the relative cost effectiveness of DDT residual spraying and of bednets impregnated with deltamethrin in the malaria control program. The trials were divided into three subgroups: (1) two farming areas and one coal mining area with a total population > 20,000, where the trial consisted of mass bednets impregnated with deltamethrin 15 mg/m2 net surface once a year, (2) one farming area with a population of approximately 3,600 where DDT residual spraying at 2g/m2 was carried out twice a year in May and August; (3) one farming area and one coal mining village with a population of > 4,000 were used as a control. The malaria vector population consisted mainly of Anopheles minimus and An. anthropophagus with a small contribution from An. sinensis. After bednets were impregnated with deltamethrin the mosquitos resting on the surface of the bednets decreased significantly, although there was less effect on the total vector population. The results showed that malaria incidence decreased significantly both in areas where impregnated bednets were used and in areas where residual spraying was undertaken. The positive IFAT rates of residents who slept under impregnated bednets decreased significantly in farming areas, especially in that area where bednet impregnation as a vector control measure had been undertaken for two years, but there was no change in the IFAT rate in DDT sprayed or control areas.(ABSTRACT TRUNCATED AT 250 WORDS)

The advantages of mosquito biocontrol by stocking edible fish in rice paddies.

Edible fish stocked in rice fields at a density of 600-800 fry per mu (1 mu = 1/15 hectare) for 150-170 days may act as an effective mosquito biocontrol agent. Common carp (Cyprinus carpio), grass carp Ctenopharyngodon idella) and Tilopia spp. killed late stage larvae and pupae of Anopheles sinensis and Culex tritaeniorrhyncus in laboratory and field trials. Stocking of fish in experimental rice fields decreased larval numbers significantly in comparison with control areas. Expansion of fish stocking in rice fields on a large scale over several years correlated with a marked decrease in malaria transmission. The addition of fish to the rice fields also resulted in increased yields. A ditch-ridge system of field arrangements is described for optimization of fish handling. Preliminary cost-benefit analysis indicates that this approach to mosquito control conveys considerable economic advantage and thus provides incentive to the community to participate in vector control programs. Farmers' experience in Guangxi over a number of years indicates that the use of edible fish for this purpose can be carried on a large, commercially viable scale.