Monitoring of cyanobacteria toxins, microcystins, in pond water at four urban park ponds was carried out every month for about two years. Total concentrations of microcystins and dissolved microcystins ranged from 0.1 to 2.3 μg/L and from 0.1 to 1.1 μg/L, respectively. Monitoring of microcystins in fountain water was also carried out as the running of fountain pumps might cause high concentrations of microcystins in fountain water. Microcystin concentrations in fountain water were similar to those in the pond water where the fountains were located. These results suggested that human health is little affected by water from these urban park ponds and fountain water containing microcystins. However, continuous monitoring of microcystins at urban park ponds is necessary because concentrations of microcystins in these ponds could increase in the future.
Methylene-bis(thiocyanate) (MBTC), an antimicrobial agent used in water-cooling systems, soluble cutting oils, and paper mills, was evaluated for its skin sensitization potency in both the induction and elicitation phases in a modified guinea pig maximization test (GPMT). MBTC showed strong sensitization potential in GPMT, so that a topical application using a patch with a relatively high concentration of MBTC (10, 000 ppm) was able to sensitize 100% of guinea pigs alone, without an intradermal injection. At a dose of 5 ppm in both the intradermal injection and the topical application, the compound produced skin sensitization in 60% of animals. The strongest positive skin reaction was elicited not in the group of animals sensitized with 5, 000 ppm MBTC, the highest induction dose tested, but in the group treated with 500 ppm MBTC. The lowest elicitation concentration was 50 ppm in groups sensitized with 50 or 500 ppm MBTC. MBTC-sensitized animals cross-reacted to benzyl thiocyanate, chloromethyl thiocyanate, and 2-(thiocyanomethylthio) benzothiazole, but not to calcium thiocyanate, methyl isothiocyanate, or methylene dicyanide. The data showed that the presence of a thiocyanomethyl group in the chemical structure of a compound is essential for cross-reactivity in MBTC-sensitized animals.