Authors: Eric P. Vejerano, Amara L. Holder, and Linsey C. Marr
Disposal of waste through incineration produces hazardous pollutants. Among them, polycyclic aromatic hydrocarbons (PAHs) and chlorinated dioxins and furans are of concern, as some of them can induce cancer, can cause mutations in genetic material, and can interfere with the proper functioning of hormones. In addition, some of these compounds can remain in the environment for a long time and be transported long distances from where they were originally released.
Nanotechnology has enabled the development of new materials, dubbed nanomaterials, that are approximately a thousand times smaller than the thickness of a human hair. The small size of nanomaterials imparts unique and novel properties not observed with their bulk counterparts. Because of these properties, they are incorporated into a wide variety of consumer products for various applications. As with any products, eventual disposal is inevitable, and some of them will be incinerated. How nanomaterials interact with waste during incineration and their influence on pollutant formation, however, are not yet understood. The small size of nanomaterials and their large surface area may enhance the formation of hazardous pollutants.
To this effect, we have conducted laboratory incineration studies of paper and plastic wastes containing nanomaterials. The emission of smaller PAH species which are emitted as gaseous pollutants increased with the addition of the nanomaterials. PAH emissions were ~6 times higher for the nanomaterials compared to their bulk counterparts. No detectable amount of chlorinated dioxins was noted both in the presence and the absence of the nanomaterials. However, among the different nanomaterials, silver and titania increased the emissions of chlorinated furans. This result is of concern as these nanomaterials are produced and used in greater volumes compared to the others. Pollutant emissions were affected by both the surface area and by the type of the nanomaterials.
Some of these hazardous pollutants will be removed from incinerator exhaust by air pollution control equipment, but open burning, which is practiced in some areas, could lead to their release into the environment. As nanomaterials are used in more and more consumer products, further studies on their environmental and health impacts are warranted.
About the author: Eric Vejerano is a postdoctoral associate at Virginia Tech.