The use of plants to assess the quality of indoor air

Plants have been used as initial indicators, or monitors, of air pollutants around industrial sources for a long time (Heck, 1966). Sulfur dioxide (S02) was early identified as causing injury to field-grown plants (Thomas, 1951; Zimmerman & Hitchcock, 1956). Ethylene has long been associated with plant damage found in greenhouses using artificial illuminating gas (Crocker, 1948; Heck & Pires, 1962) ethylene associated with auto exhaust caused severe orchid losses in greenhouses in the San Francisco area (James, 1963).Gaseous fluorides (i.e., HF) from aluminum smelting, super phosphate production and  other processes have been monitored by a variety of plant species/cultivars (Zimmerman & Hitchcock, 1956; Hitchcock, Weinstein, McCune & Jacobson, 1964; Weinstein, 1961). The photochemical complex [principally ozone (03)] has been extensively studied and several plant systems have been used to monitor this complex (Middleton, 1961; Darley, Dugger Jr., Mudd, Ordin, Taylor & Stephens, 1963). Early work utilized native plants as indicators of pollutants and characterized injury symptoms under natural conditions. The field survey includes visual symptomology and may include chemical analysis of plant tissues. Plant physiologists have used plants under controlled conditions to estimate concentrations of certain chemicals. This bioassay method has been used to monitor air pollutants both as a supplement to the field survey method and to monitor in studies involving various mixtures of chemicals (to distinguish specific toxicants or classes of toxicants). This paper summarizes several ambient monitoring programs used to assess air pollutant effects on biological systems. It also develops a rationale for use of these techniques to assess the possible biological impact on indoor air quality.