Engineered nanoparticles (ENPs) are used in many applications. For example, carbon nanotubes (CNTs) are used in biosensors, as electrically conductive polymers, to reinforce concrete, to remove biological contaminants, and for tumor imaging. Enormous amounts of (ENPs) are produced globally. For example, annual demand for CNTs was estimated to increase from 3,700–4,100 tons in 2013 to 5,300–5,720 in 2015 to 10,500–12,000 in 2020. CNTs and other ENPs will eventually end up in aquatic and terrestrial systems. While the promise of these ENPs for humans is vast, the knowledge on ecological impacts is unknown. I tested the effects of pure single walled CNTs on consumption and growth of Diamondback moths (Plutella xylostella). My goals were to establish baseline concentrations of pure carbon nanoparticles that would deter feeding or be toxic in the gut of the insect, and determine if plants grown in media containing CNTs would affect insect consumption or growth. Moths were either feed artificial food that contained CNTs or Arabidopsis thaliana grown in CNTs. Both the plant and insect are model organisms (e.g., genome sequenced, moth is resistant to many insecticides and the first insect to evolve resistance to Bt toxins in open-field populations).
Results/Conclusions
I have established concentrations of pure CNTs, at concentrations produced for manufacturers of items that incorporate them into a product, that have mildly toxic effects on larvae. To date I have assayed concentrations in artificial food from 4 mg/L to 17 mg/L. In artificial food containing this range of CNTs, there has been no evidence of deterrence (i.e., consumption rates are not affected). However, the 4 mg/L concentration significantly increased growth and time to pupation, while the 17 mg/L concentration significantly reduced growth, and time to pupation. The mechanism is likely changes in gut flora that enhance or reduce assimilation of food, which will be examined in the future using PCR. In addition, at concentrations above 8 mg/L, larva have reduced fecundity. I found no effects on consumption or growth of larvae feed A. thaliana grown in a media containing 24ug/ml of CNT. Pure ENPs are not the form that will be primarily found in the environment, their functionalized and weathered form will be what accumulates; however, the ecological science is in its infancy and effects of all forms of ENPS on organisms, food webs, and ecosystems needs to be studied.