In Southeast Asia the aquatic macrophyte water spinach (Ipomoea aquatica Forsk.) is a popular vegetable that is cultivated in freshwater courses. These often serve as recipients for domestic and other sorts of wastewater that often contain a variety of pollutants, such as heavy metals. In addition, fertilizers are frequently used where water spinach is cultivated commercially for the food market. To estimate the importance of ambient nutrient concentrations for accumulation of mercury (Hg), cadmium (Cd), and lead (Pb) in water spinach, plants were exposed to nutrient solutions of different strength and with varying metal concentrations. Metal-induced toxic effects, which might possibly affect the yield of the plants, were also studied. The lower the nutrient strength in the medium was, the higher the metal concentrations that accumulated in the different plant parts and the lower the metal concentration in the medium at which metal-induced toxic effects occurred. Accordingly, internal metal concentrations in the plants were correlated to toxic effects. Plants exposed to metals retained a major proportion of the metals in the roots, which had a higher tolerance than shoots for high internal metal concentrations.

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The aquatic plant water spinach (Ipomoea aquatica), either wild or cultivated, is found throughout Southeast Asia and is a widely consumed vegetable in the region. Many of the waters where I. aquatica grows serve as recipients for domestic and other types of wastewater. Because these waters contain not only nutrients, but often also a wide variety of pollutants such as heavy metals from various human activities, many people risk intoxication. To estimate the accumulation of lead (Pb), cadmium (Cd), total mercury (total Hg), and methylmercury in I. aquatica and the potential hazard to human health via consumption, nine sites for cultivation of I. aquatica in the greater Bangkok region of Thailand were sampled. At seven of the sites, I. aquatica was cultivated for the local food market. The concentrations of methylmercury, total Hg, Pb, and Cd in I. aquatica were 0.8 to 221, 12 to 2,590, 40 to 530, and < or = 10 to 123 microg/kg dry weight, respectively. At all sites at least one element showed relatively high concentrations and no reference site could be established. From threshold values for highest tolerable intake of these metals by humans and information about consumption of I. aquatica among local people, Pb and Cd concentrations in I. aquatica do not seem to be a direct threat to human health. However, concentrations of Hg were very high at some sites, and were higher in leaves (highest mean value: 1,440 microg/kg dry wt) than in stems (highest mean value: 422 microg/kg dry wt). This might be a threat, especially to children and fetuses, because Hg in I. aquatica was composed of methylmercury, partly or totally, at most sites to 11% or less and at one site from 50 to 100%. At the latter site, I. aquatica was not cultivated for the food market. Because other food sources, such as fish, may have high concentrations of methylmercury, these results indicate a need for monitoring of Hg, especially methylmercury, in different foodstuffs in the region.

The aquatic plant water spinach (Ipomoea aquatica), either wild or cultivated, is found throughout Southeast Asia and is a widely consumed vegetable in the region. Many of the waters where I. aquatica grows serve as recipients for domestic and other types of wastewater. Because these waters contain not only nutrients, but often also a wide variety of pollutants such as heavy metals from various human activities, many people risk intoxication. To estimate the accumulation of lead (Pb), cadmium (Cd), total mercury (total Hg), and methylmercury in I. aquatica and the potential hazard to human health via consumption, nine sites for cultivation of I. aquatica in the greater Bangkok region of Thailand were sampled. At seven of the sites, I. aquatica was cultivated for the local food market. The concentrations of methylmercury, total Hg, Pb, and Cd in I. aquatica were 0.8 to 221, 12 to 2,590, 40 to 530, and < or = 10 to 123 microg/kg dry weight, respectively. At all sites at least one element showed relatively high concentrations and no reference site could be established. From threshold values for highest tolerable intake of these metals by humans and information about consumption of I. aquatica among local people, Pb and Cd concentrations in I. aquatica do not seem to be a direct threat to human health. However, concentrations of Hg were very high at some sites, and were higher in leaves (highest mean value: 1,440 microg/kg dry wt) than in stems (highest mean value: 422 microg/kg dry wt). This might be a threat, especially to children and fetuses, because Hg in I. aquatica was composed of methylmercury, partly or totally, at most sites to 11% or less and at one site from 50 to 100%. At the latter site, I. aquatica was not cultivated for the food market. Because other food sources, such as fish, may have high concentrations of methylmercury, these results indicate a need for monitoring of Hg, especially methylmercury, in different foodstuffs in the region.

No abstract