The scientists analyzed water pollution in Bosten Lake from 2000 to 2009 using a tool called principal component analysis. They found that in 2000, the lake had the worst pollution in the past decade. However, over the years, the overall pollution score decreased, showing improvement. Despite this decline, pollution in the lake was still a concern, with a spike in pollution levels in 2005. This suggests that efforts to improve water quality in Bosten Lake need to continue to ensure it meets satisfactory standards.