SAN FRANCISCO As California continues to weather its worst blazes in state history, the specific impacts of wildfire smoke on human health continue to elude scientists.

Since igniting earlier this month, the cluster of fires in the states Wine Country have killed more than 40 people and destroyed at least 5,700 structures , but the consequences extend to far beyond those in the blazes path. The fires have created a record high amount of air pollution spreading across the San Francisco Bay Area about as much produced by cars in the state in a given year, one air quality analyst told CNN . But scientists also say more research is needed to understand how wildfire smoke affects residents health.

That smoky, polluted air is full of microscopic pieces of particulate matter around 2.5 micrometers or smaller, or PM 2.5, which are too small to be caught by our lungs filtration system and instead enter our bloodstreams. Those particles are what turned skies brown and hazy as far as San Francisco 50 miles away, prompting warnings to stay indoors and coughing, wheezing and other side effects among many of those exposed to the abysmal air.

Numerous studies have linked premature death in people with heart or lung disease, heart attacks, asthma and other respiratory issues to inhalation of such particles, which are also emitted year-round by vehicles and other pollution sources. Other recent studies have linked PM exposure to increased kidney disease risk and shortened lifespans of those exposed to it in the womb.