Nanotoxicology - small particles with unique toxicity from aquatic to human model systems Tara Sabo-Attwood, PhD University of South Carolina NCSU Workshop on Communicating Health and Safety Risks on Emerging Technologies

Today’s talk (from an environmental molecular toxicologist point of view)  Nanomaterials in the environment – challenges of assessing unintended exposures  Influence of public perception on science  What have we learned? Unexpected effects

Nanomaterials Represent a Novel Form of Contaminants in the Environment Not a question of “IF” but “WHEN” & “WHAT”…

Complex webs and networks Challenges of assessing environmental exposures

If nanoparticle X moves from consumer product to soil to groundwater countless scenarios of how these particles could impact drinking water

Nature 444, (16 November 2006), Safe handling of nanotechnology Andrew D. Maynard et al. How to study safety of nanomaterials? Public perceptions are not static “Communicating research on nanotechnology risks and benefits outside the scientific community is challenging, but is essential for a risk dialogue based on sound science. This means developing communication activities that enable technical information to be summarized, critiqued and ultimately synthesized for various interested parties, including decision-makers and consumers. The advent of the Internet provides an ideal venue for such activities and we encourage its use in communicating with the end-users of risk-based science”.

Fundamental Knowledge of the Environmental Impacts of Nanomaterials Effects of Environment and Living Systems on Nanomaterials Fate and Transport Aggregation Surface Change Adsorption Partitioning Compartment Modeling Effects of Nanomaterials on the Environment and Living Systems Bioaccumulation Biomagnification Biodiversity Metabolism, Reproduction Quality of Life Food Web Modeling Nanomaterial Production, Standard Reference Materials, Analytical Methods to detect Nanomaterials in the Environment and Living Systems RISK ASSESSMENT

Public influences risk management and toxicological science (which particles, fate, transport, route etc) Risk assessment/management Public

A number of genes altered are involved in cell cycle regulation and mitochondrial/electron transport function Some are similar to gene changes observed with asbestos Electron transport genes altered27 Cell cycle genes altered32 # of genes altered by asbestos55 Lung epithelial cells exposed to SWNT

Which nanoparticles are toxic and which are not? If so, what inherent properties govern toxicity? Challenge – not all scientists agree (impact trust, perceived benefit etc) What have we learned so far?  Are gold nanoparticles biologically inert? Plants and human cells exposed to gold nanoparticles  toxicity of synthesis byproducts - marine invertebrates (copepods) and human cells exposed to SWNT  Subtle unusual effects - freshwater fish (medaka) exposed to silver nanospheres

Gold nanoparticles - biologically inert ? Tobacco seedlings were exposed to gold nanospheres (3.5 or 18 nm) 3.5 nm spheres were taken up via roots and distributed throughout plant

Tomato plants exposed to 3.5 nm gold spheres for 5 days. Microarrays performed on leaves and roots. Results: Leaves with at least 2-fold change in expression between control and exposed Roots with at least 2-fold change Common genes to leaves and roots Leaves Roots But no metallothionein, wound or pathogen response genes Mechanisms of toxicity – gene profiling Gold nanoparticles - biologically inert?

Effective surface charge (mV) Aspect ratio PAA-coatedCTAB-capped ± ± ± ± ± ± ± ± ± ± ± ±0.6 1 AR=1AR=2.1AR=2.6AR=2.9AR=3.4AR=4.1 Gold nanoparticles - biologically inert ? safe particles by design?

SWNTs –Electrophoretic Purification (Xu et al., 2004) Purified SWNTs: nominal molecular weight (NMW) >100K Short tubular nanocarbon: NMW = 50K – 100K Fluorescent Nanocarbon: NMW = 12.5K – 50K What about particle synthesis byproducts?

AP-SWNT Pure SWNT Fluorescent nanocarbon Effects of SWNT on copepod nauplius – adult development What about particle synthesis byproducts?

0 ppt 25 ppt 10 mg L -1 SWNT in 10 mM phosphate buffer/synthetic seawater solution (pH 7.8) Napthalene Do ‘new’ materials influence toxicity of ‘old’ materials

Bioavailability factors for PCBs and PBDEs Error bars represents ±1 sd. Significant differences relative to HOC only treatment are denoted with an *

Freshwater fish (Medaka) exposed to silver nanospheres Fish embryos were exposed in water to 10 ppm silver-colloid nanoparticles (4 nm diameter, commercially available) After 5 hours, the embryo architecture is completely destroyed Environmental concentrations will likely be times lower. Unusual effects

Age-Dependent Toxic Effects of Ag-Nanocolloids in Medaka Embryos. Embryo stageStage 11 Stage 21 Stage 30 Ag-nano (mg/L) Inhibition of Blood vessels Blood clot (%) *000 Percardiovascular edema and tubular heart (%) * Heart beat (15 sec) NA Hatch ratio (%) * * Hatch error (%)00NA Spinal deformity (%) 03.3NA023.3* * Hatch time (day)9.08.4NA *ANOVA P<0.05.

What does all this mean (as toxicologists)? Our understanding of the potential toxic effects of nanomaterials is more complex than originally thought Daunting challenge – so may nanomaterials, byproducts etc classic toxicological paradigms need to shift to a more interdisciplinary approach including modeling and forcasting But how do we do this? How will this effect risk communication?

RiskAssessmentRiskManagementRegulatoryProcess Risk Communication SCIENCE REGULATIONS RiskCharacterizationRegulatoryDecision Adapted from “informing the public and involving them in the risk assessment and risk management processes.”

Lee Ferguson John FerryCathy Murphy Tom ChandlerAlan Decho Gene Feigley Shosaku Kashiwada Sean Norman NanoenvironmentalTeam Research Triangle Institute (RTI) and Dr. Wally Scrivens (USC Dept. of Chemistry): 14 C-SWNT synthesis collaboration Funding: EPA STAR, NSF, USC research foundation Acknowledgements