Research into pollution by scientists at the National Aeronautics and Space Administration in the 1980s led to the promotion of indoor plants to combat sick building syndrome. Volatile organic solvents such as benzene, however, also affect the plants that transform them.
Benzene is composed of six atoms of hydrogen and six atoms of carbon. It is a clear to yellowish solvent known as a volatile organic solvent (VOC). Benzene is found in cigarette smoke, pesticides, industrial wastes, auto exhaust and smog. It is also a product of natural sources as volcanic gases and decaying plant matter. Phytoremediation refers to the ability of plants to remove VOCs like benzene in closed systems and produce oxygen.
Carbon is a basic building block of plant life. Plants are able to synthesize chemicals such as carbon dioxide and formaldehyde that are toxic to animals. Plants can use benzene by breaking it down into sugar and water. They begin the process of phytoremediation with the photosynthesis to separate the carbon and hydrogen.
The free hydrogen formed by photosynthesis combines with oxygen in the air to form water vapor that falls from leaves to the soil. As the water falls, it gathers more airborne benzene. Plant roots soak up the water as well and the molecules that cling to it and use the components to produce more food for the plant.
Plants easily absorb benzene up to a certain threshold. Once that threshold is met, the plant basically overdoses on the solvent. A study published in the "Brazilian Journal of Microbiology" found that some compounds containing benzene slowed the growth of a common fungus and some compounds actually changed how the fungus grew. Once a plant's tolerance threshold is reached, growth may slow or plant pores may be overcome, killing the plant. Studies of a common benzene component in pesticides showed no effect at low concentrations, growth stimulation at intermediate concentration and slower transpiration and growth at higher concentrations when used on sorghum.
Different benzene concentrations and compounds appear to affect different types of plants in diverse ways. Although benzene does not appear to promote plant growth overall, most plants appear to be able to absorb a certain amount of the chemical without damage. Some benzene compounds, however, demonstrate destructive potential in plant cells much like that in animals where benzene is considered a carcinogen.