I have read, with great interest some of your statements and a presentation of yours on indoor air pollution resulting from close proximity to highways. My wife and I are considering a relocation, in order to decrease my commute time. However, almost every property we look at is within 1.5 miles of a major highway, which is often congested with trucks, etc. I have read over 10 studies documenting increased risk for childhood leukemia and asthma. What is considered a"safe distance" from a major highway? These studies don't state the exact distance at which they measured. Also, I have read of the ability of plants such as bamboo and areca palm in removing 80% of benzene in the air. Have you read those claims and do they seem to be valid?
You are right that many recent studies have shown that pollution from traffic, especially diesel-powered traffic (such as trucks) is bad for health. Traffic pollution has been linked to increased death and hospital admissions for heart and lung disease, increased asthma attacks, and early indicators of cardiac disease. Consistent with these findings, several studies have also shown that living near a major highway or road presents greater health risks. While there have been some differences among studies, there seems to be a general consensus that the critical distance from a busy road or highway is within 100 meters (or about 300 feet). After this distance, you generally no longer see a dramatic increase in traffic-related pollution above urban background. In a city, however, it is difficult to get away from all traffic-related pollution as it can travel relatively long distances.
It is not clear what pollutant or pollutants emitted from motor vehicles are responsible for the observed health problems. It is possible that plants (such as bamboo) under certain conditions can be used to remove certain gaseous pollutants from motor vehicles, such as benzene, carbon monoxide and nitrogen dioxide. I haven't heard of any plants that remove particles from motor vehicles. l think that most of the studies examining pollutant removal by plants have been conducted in closed environments. The effectiveness of using plants to clean your air in your yard will probably be much lower, as outdoor air moves pretty freely.