A Japanese professor has blamed high levels of mercury in frost in forests in southern Japan on pollution from China. The study, by Osamu Nagafuchi, a visiting professor at the Fukuoka Institute of Technology, coincides with a United Nations treaty on the use of and trade in mercury going into effect, but will also raise new fears in part of Japan that has become synonymous with one of the worst cases of mercury poisoning. Nagafuchi has been monitoring pollution in Kyushu and the surrounding islands for nearly three decades and has previously blamed the die-off of the primeval forests on the Unesco World Heritage island of Yakushima on airborne pollutants from China. As far back as 1992, Nagafuchi began monitoring patches of blackened snow in remote areas of the island. Subsequent analysis revealed traces of silicon, aluminium and other by-products of the burning of coal in homes and thermal power plants in China. Over the years, he has been able to link higher pollution levels in Kyushu to when the winds are blowing from the northwest. Beijing and Tianjin are around 1,450km northwest of Kyushu. Nagafuchi’s research has also identified climbing mercury levels in winter frosts across Kyushu. Before 2010, mercury concentrations in frost on trees in Yakushima and on Mount Tsurumi in Oita Prefecture were less than 100 nanograms per litre of water. In 2013, tests on Mount Karakuni revealed 160 nanograms per litre of water, but soared to 400 nanograms the following year. Levels in January this year had declined to 60 nanograms, the Mainichi newspaper reported, a reading that Nagafuchi said is because of air currents deviating from their usual paths and a temporary phenomenon. According to the United Nations Environment Programme, around 1,960 tonnes of mercury are released into the atmosphere every year, with emissions from China accounting for about one-third of that total. On Wednesday, the UN Minamata Convention on Mercury took effect. It is designed to control the use of the poisonous chemical element. The treaty is named after the Kyushu city where thousands of local people were struck down by severe mercury poisoning after eating fish caught in local waters. Unknown to the residents, Chisso Corp had been releasing methylmercury into Minamata Bay from 1932, where it had built up in marine life. The disease was first identified in 1956 but releases of tainted water went on into the 1960s. More than 10,000 people have been affected and 2,265 have died. Others have suffered insanity, paralysis and comas.