By Chuck Chiang British Columbians are being told to prepare themselves for the worsening of a dense shroud of wildfire smoke that has descended over the province, with health experts saying the dangerous impacts of the pollution might not be immediately apparent. Forests Minister Ravi Parmar told a briefing on Wednesday that the smoke would be a “major factor” in the next 24 to 72 hours, with more arriving in the central and southern Interior in the evening or on Thursday, and reaching the Fraser Valley by Friday. “We should expect wildfire smoke to come south in the days ahead,” Parmar said, adding that the smoke was coming from fires in B.C., Yukon and the Northwest Territories, as well as from the United States. After a summer of relatively clear…