There has been speculation that fuel switching may have been a contributing factor to the increased ozone levels in the Los Angeles area during the recent smog alert. The rationale for the speculation is that automobiles equipped with catalytic converters emitted increased hydrocarbons (which through photochemical reactions form ozone) because of the reduced effectiveness or deactivation of the catalyst caused by the use of leaded fuel, many studies are being conducted to quantify the effect of such misfueling on the amount of pollutants emitted. However, this paper focuses on another factor related to the reduced capacity of the catalyst which also is viewed by some as a contributor to the air quality problem. The problem is the suspected inadequate performance of the catalyst due to the effects of deterioration from aging or mileage accumulation. The 'useful life' of light-duty vehicles has been defined as 50,000 miles or 5 years in Federal regulations. It is thought by some that the effectiveness of the catalyst on vehicles that are beyond their 'useful life' is drastically reduced. The higher mileage vehicles may contribute to increased hydrocarbon levels since many catalyst equipped automobiles now on the road have reached the 5 year or 50,000 mile mark.

"EPA-AA-TEB-80-5." "December 1979." Cover title.