Buildings in the 1970s were made more airtight than nowadays. Which was beneficial both for the state and for building owners allowing them to reduce costs with annual kWh savings goals.
Sealing up buildings reduced the ventilation rate per person per minute to 5 cubic feet. After that, the American Society of Heating, Refrigeration and Air-Conditioning Engineers reviewed and updated ventilation standards to a minimum of 15 cubic feet per person per minute.
External pollutants such as exhaust fumes and vapors, containing substances such as carbon monoxide, radon, formaldehyde, and asbestos can enter through poorly located air intakes. Inside, we consume air with particles of volatile organic compounds from adhesives, carpeting, upholstery, copy machines, pesticides, synthetic fragrances, etc.
Some state governments established rules for the compliance of the premises with acceptable levels of gaseous air pollutants, others continue to adhere to the conservative tradition.
Some house plants might help too. A study out of the University of Cologne in Germany found that certain plants can absorb air pollutants.