Why do the outdoor air monitoring data summaries only go back to 1980? Isn’t older data available?

While older monitoring data are available in AQS, we use 1980 as the first year for tracking trends because that year marks the beginning of nationally consistent operational and quality assurance procedures for air quality monitoring, particularly for ozone. PM10 monitoring began in many areas around 1987-1988. PM2.5 monitoring was phased in during 1999-2001. Our AQS database shows monitoring data from a few monitors in Los Angeles County – as far back as 1957 for total suspended particulate; 1963 for carbon monoxide, nitrogen dioxide, and sulfur dioxide; and 1974 for ozone. We do not use this older information to calculate trends because of uncertainties in the results. Monitoring methods have improved significantly since this time.