> <i>The World Health Organization estimates that 80 percent of people living in urban environments are being exposed to unhealthy levels of air pollution from particulates and it says they cause four million deaths annually around the world.</i><p>The level of particulates middle-class people face indoors in the worst urban environments is tiny compared to the level of particulates people face (esp. in rural areas) wherever cooking is done indoors over a wood fire. We’re talking about a level of wood smoke filling the room which causes eyes to redden and start watering, and makes it physically difficult to breathe. (Source: my parents are anthropologists and my godparents are indigenous rural Mexican peasant farmers, and I spent lots of time growing up sitting next to wood-burning hearth fires.) On average, by historical standards, humans’ current exposure to particulates is very low and continues to drop every year.<p>I don’t know if it makes sense for people to freak out about cooking eggs in their houses, though having effective indoor ventilation is obviously worthwhile, all else equal.<p>Edit: I looked up the actual WHO source (not linked in the OP): <a href="http://www.who.int/mediacentre/news/releases/2014/air-pollution/en/" rel="nofollow">http://www.who.int/mediacentre/news/releases/2014/air-pollut...</a><p>> <i>After analysing the risk factors and taking into account revisions in methodology, WHO estimates indoor air pollution was linked to 4.3 million deaths in 2012 in households cooking over coal, wood and biomass stoves.</i><p>This is <i>not</i> talking about people using a gas range with an underpowered ventilation hood to cook eggs, and the 4 million deaths number is not restricted to urban areas. The people dying here don’t need a little electronic air quality detector, they need electrification and rising incomes so they can afford better heaters and stoves.<p>To cut outdoor air pollution, we should get people to stop burning piles of trash, stop using fire to clear large areas for agriculture, switch away from coal power plants as soon as possible, and try to get the worst polluting old vehicles off the roads.