Do you happen to live in an apartment building? In my case, pollution from the downstairs neighbors would affect my apartment. Especially cigarette smoke, which my neighbor only smokes indoor in the morning.
Cooking breakfast is also a huge source of pollutants.
For my apartment, highest polluters include: dishwasher heating cycle, cooking, neighbor cigarette smoke, and air leaking in from main door. Adding weather stripping on the main door has substantially reduced the ambient pollution levels of my unit.
Cooking breakfast is also a huge source of pollutants.