Martínez Hernández Juan, López-Rodas V, Costas E
Servicio de Medicina Preventiva, Hospital Carlos III, C/Sinesio Delgado 10, 28029 Madrid, Spain.
Med Hypotheses. 2009 May;72(5):539-40. doi: 10.1016/j.mehy.2008.11.041. Epub 2009 Feb 11.
An increasing number of people drink water from fresh water supply reservoirs. However, with the global change a lot of reservoirs become eutrophic, which facilitates the occurrence of toxin-producing cyanobacterial blooms. Microcystins (powerful hepatotoxic water-soluble heptapeptides) are the most important cyanobacterial toxins affecting humans. High doses of microcystins produce hepatic necrosis. Consequently, WHO Guidelines limit microcystins to 1 ppb in drinking waters. However, microcystins are present frequently in tap water at lower doses. Here, we hypothesized that chronic consume of tap water containing low doses of microcystins may be a risk factor for liver and colorectal cancer. Two kinds of evidences support this hypothesis. On one hand some epidemiological data (mainly in China). On the other hand, the molecular mechanism of microcystins toxicity (inhibition of protein phosphatases PP1 and PP2) is just like okadaic acid (a potent tumor promoter). Cancer risk from drinking water is certainly less than smoking, occupational exposures or some foods. But it is significant and with a rapid increase of toxic cyanobacterial blooms by eutrophycation, become more frequent.
越来越多的人饮用来自淡水供应水库的水。然而，随着全球变化，许多水库变得富营养化，这促使产生毒素的蓝藻水华发生。微囊藻毒素（强大的肝毒性水溶性七肽）是影响人类的最重要的蓝藻毒素。高剂量的微囊藻毒素会导致肝坏死。因此，世界卫生组织指南将饮用水中的微囊藻毒素限制在1 ppb。然而，微囊藻毒素经常以较低剂量存在于自来水中。在此，我们假设长期饮用含有低剂量微囊藻毒素的自来水可能是肝癌和结直肠癌的一个风险因素。有两类证据支持这一假设。一方面是一些流行病学数据（主要来自中国）。另一方面，微囊藻毒素毒性的分子机制（抑制蛋白磷酸酶PP1和PP2）与冈田酸（一种强效肿瘤促进剂）相似。饮用水带来的癌症风险肯定小于吸烟、职业暴露或某些食物。但它很显著，而且随着富营养化导致有毒蓝藻水华迅速增加，这种风险变得更加频繁。
