Dr. Renaud Vincent and his colleagues of Health Canada, Ottawa, hypothesized that ambient PM would cause changes in certain cardiovascular parameters. The investigators implanted rats with radiotransmitters to collect continuous data and indwelling catheters for repeated blood sampling. The animals were exposed to clean air or one of four types of resuspended particles: ambient particles (Ottawa dust), ambient particles that had been washed in water to remove soluble components, diesel soot, or carbon black. The investigators used stored resuspended particles rather than fresh particles to ensure that particle concentration and chemical composition were identical among experiments. Endpoints measured in the rats' blood and plasma include changes in heart rate, blood pressure, general activity, and injury to lung tissue.