Many of Taipei County's fast food restaurants have poor air quality, with 60 percent of those inspected suffering from excessive amounts of bacteria, according to the results of a survey made public Friday by the county's Environmental Protection Bureau. Out of 24 McDonald's, KFC, and Mos Burger outlets tested since February, some 60 percent had high bacteria levels and 30 percent had excessive amounts of carbon dioxide. One of the Japanese-style burger outlets even had higher than normal levels of formaldehyde, the survey showed. Bureau officials attributed the high levels of pollutants to the enclosed environment of most restaurants and suggested that Japanese-style restaurants in particular are vulnerable because of the anti-corrosion solvents found in their predominantly wooden decor. Despite the lack of legislation requiring restaurants to lower the level of bacteria and other harmful substances, many local fast food shops indicated their willingness to collaborate with the bureau in trying to clean up their air, the officials said. A high level of carbon dioxide usually causes fatigue and concentration difficulties. An excessive amount of formaldehyde can irritate one's respiratory system and may cause cancer, the officials said. One of the suggestions made by officials to help the chains keep the air fresh in their restaurants was to have them place potted green plants in corners of the restaurant. 