Page 470 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

Ecotoxicological Impacts of Nanomaterials 447

Many examples in modern history illustrate the unintended conse-
quences of initially promising technologies, including the blind release
of “beneficial” chemicals into the environment, such as asbestos or
DDT. These examples forewarn us of potential environmental impacts
of some nanomaterials, which deserve more attention and research
[16–18]. Furthermore, the large intellectual and financial investments
in nanotechnology demand that it be publicly accepted and sustainable
[19]. The backlash against genetically modified crops resulted in a
huge setback for agriculture. A similar backlash against nanotech-
nology would result in the delay of beneficial nanomaterials coming to
market.
The matter of determining whether or not a substance is “dangerous”
involves not only determining any hazards presented by the material
such as toxicity, but also to what degree the material contacts living
organisms. Currently, the degree to which cellular processes and ecosys-
tem health may be impacted by nanomaterials, let alone specific toxic-
ity mechanisms, remain largely unknown. This chapter discusses the
known and postulated interactions between nanomaterials and non-
mammalian biological indicators, specifically microbes, and how these
relationships foreshadow the potential effects of nanomaterial releases
into the environment.

Why Study the Effects of Nanomaterials
on Microorganisms?
Microbes are present in almost every environment on earth, and their
flexibility and adaptability allow them to survive under seemingly unliv-
able conditions, such as anaerobic, high heat, or extreme cold conditions.
Microbes as a whole produce the majority of the biomass in aquatic sys-
tems. While plants are the primary biomass in terrestrial systems, their
survival depends on the activity of microbes for the breakdown of dead
matter and the recycling of needed nutrients. Microbes play key roles
in the cycling of carbon, nitrogen, phosphorous, and other minerals.
Microbial ecotoxicology is therefore a particularly important consider-
ation because microorganisms serve as the basis of food webs and the
primary agents for global biogeochemical cycles. Microorganisms are
also important components of soil health and could serve as potential
mediators of transformations that affect nanoparticle mobility and tox-
icity in the environment.
One benefit of evaluating microbial toxicity is the ability to extrapo-
late the observed effects of chemicals on microbes to other higher level
organisms. Quantitative structure activity relationships (QSARs) are
one way to calculate the impact on other organisms based on chemical
structure [20]. QSARs incorporate mathematical relationships between