Canadian wildfires in Manitoba and Saskatchewan have prompted air quality alerts in Minnesota, Wisconsin and Michigan on Wednesday and Thursday as residents are advised to "limit prolonged or heavy exertion." Why It Matters The elevated levels of fine particulate matter resulting from wildfire smoke could present significant health risks, especially for people with asthma, heart disease or other preexisting respiratory conditions. State and local health officials have urged those in the affected areas to limit outdoor activities and remain indoors while conditions persist. Canadian wildfires have been of recent concern to Americans who live in bordering states, as hundreds of...