evaluating the safety of nanomaterials
TRANSCRIPT
Managing Uncertainty
Evaluating the Safety of Nanomaterials
Annette Santamaria, PhD, MPH, DABT
ENVIRON International Corporation
TAPPI Conference
June 25, 2008
Managing UncertaintyPresentation Summary
Overview of Nanomaterials
Toxicological Concerns
Forestry Product Uses
The promise of nanotechnology is the potential to fulfill societal demands for novel applications and products that could result in a substantial improvement in the quality of life.
Managing UncertaintyConcerns About Nanomaterials
Bloom ☺Better productsFaster technologyImprove quality of lifeSolve energy problemsImproved drugs, medical devices, electronics
Gloom Little toxicological data or studies and no epidemiological studiesLittle exposure dataWhat level of protection needed?Challenges current principles of environmental, human health, and occupational toxicology Need for increased funding for EHS implicationsChanges to current regulations?
Managing UncertaintyWhat’s so Special about Nanos?
Unique physicochemical properties --enhanced electrical, thermal, physical, magnetic, and quantum properties
Physical, chemical, toxicological properties macroscale particles largely understood
Physical/chemical properties of same materials on nanoscale may be different
Toxicological properties of nanomaterials likely to be differentas well
?
NanoparticlesFine particles
Managing UncertaintyWhat is the Basis for Increased Concern?
Increased reactivity because of increased surface area and/or surface properties?
Different Kinetics?Ability to reach deep airwaysDermal penetrationSystemic distributionPenetrate blood-brain or placental barriers
Biological persistence“New” toxicities from engineered nanomaterials?
Dendrimers with nanoparticles of drugs
Paul Trombley, U Michigan Center for Biologic Nanotechnology
Managing Uncertainty
Physicochemical Properties of Nanomaterials
MassSize distributionSurface areaParticle numberShape/structureChemical compositionSurface coatingsPuritySurface chargeAggregation potential
Nanoparticles, http://www.northwestern.edu
Managing Uncertainty
Potential for generation of free oxygen radicals DNA damage inflammation tissue damage
respiratory or cardiovascular effects, cancer?
Relationship Between Particle Size and Number of Surface Molecules
Nel et al. 2006
Managing UncertaintyZinc Oxide – Various Shapes
Wang 2004
Managing UncertaintyBasis for Toxicological Concern
Studies with nanoparticles (carbon black, titanium dioxide, iron oxides, silica) that have been used for decades suggest the potential for adverse health effects
Air pollution studies provide evidence for the role of combustion-derived nanoparticles in respiratory and cardiovascular effects
Recent in vitro and in vivo studies with nanomaterials suggest potential for oxidative stress and immunological responses
Managing UncertaintySocietal Concerns
Occupational health and safety
R&D labsuniversitiespiloting and ramping-up operations/facilitiessmall businesses
Consumer health and safety
Waste discharge into the communities, environment
Managing Uncertainty
Evaluating Hazard and Exposure Potential
Physical & Chemical
Characterization
Size & shapeCompositionSolubilityStabilityMassSurfacePurity
Immune responseCytotoxicityMechanisms of action
ADMEHazard potentialDose response
MobilityFateTransportTransformationEcotoxicology
In vitro In vivo Environmental
Managing UncertaintyMinimal Hazard Information to Date
Most data in vitro or short-term in vivo studies on a few nanomaterials
Nanoparticles can enter body via inhalation, little evidence of skin penetration or gastrointestinal absorption
Particles may be transported via blood or lymphatic system to other organs
Some nanoparticles more potent than larger particles of same material
Carbon nanotube studies indicate increased inflammatory response, early markers of mesothelioma
Managing UncertaintyExposure Potential for Nanomaterials
Is human and environmental exposure likely?
An evaluation should be made of the likelihood of human and/or environmental exposure resulting from emissions throughout the life-cycle, including the manufacturing process, the various anticipated uses, and the final disposal or recycling processes
May require new equipment for measuring nanomaterials in the workplace, environment, and consumer products (e.g., release of nanomaterials from their matrix)
Managing UncertaintyPotential for Release and Exposure
Tsuji et al. 2006
Managing UncertaintyExposure Assessment – Data Gaps
Agglomeration may limit exposure to nanoparticles
The health-related importance of agglomerated nanoparticles as opposed to single discrete nanoparticles should be evaluated
Exposure to nanoparticles may be more likely to happen after the manufacturing process and during product formulation
Product matrix may limit exposure potential
Processes or situations involving friction or wear could increase exposure to nanoparticles
Managing UncertaintyEnvironmental Exposure Issues
• Ecotoxicological properties
• Will nanomaterials behave the same as other chemicals in the environment?
• Likely but additional research is needed
• Fate and transport Issues:• Mobility in air, soil, and water • Mechanisms of degradation and
transformation• Bioaccumulation
• Waste disposal• Utility of current control technologies
Managing UncertaintyNanomaterials in Forestry Industries
• Green chemistry & sustainable manufacturing
• Cellulose in biofuels & other composites
• Forest biorefinery• Production of nano-sized silica
sol for paper• Silica filler in particle retention
systems
Some potential applications include:
Managing UncertaintyNanomaterials in Forestry Products
1) Use of nano-sized building blocks to assemble materials with higher strength
2) Improve surface properties and functionality
3) Improve wood-based material processing • aiding in water removal and
eliminating rewetting• reducing energy usage in
drying• tagging fibers, flakes
4) Developing intelligent wood & paper-based products with an array of nanosensors built in to measure:• forces & loads• moisture levels, temperature,
pressure• chemical emissions• degradation by fungi
5) Building functionality onto cellulose surfaces at the nano-scale for:• pharmaceutical products• self-sterilizing surfaces• electronic devices
Managing Uncertainty
Examples of Nanomaterials in Paper, Inks, and Other Applications
Nanoparticles for pesticides and repellants
Nanocatalysts for chemical processes
Nanosensors for detection
Self-cleaning surfaces
Durable & less-expensive surfaces & adhesives
Nano-optics and devices for heat and light exclusion
Managing UncertaintyResearch Needs for Nanomaterials
Whether there is a significant risk of migration of nanoparticles from products or surface coatings
Whether nanosized materials bind to proteins or other biomolecules, agglomerate, or remain as free particles in vivo following inhalation or oral exposure
Can nanomaterials penetrate skin; if yes, what are the consequences?
Managing UncertaintyResearch Needs for Nanomaterials
Effect of nanomaterials on the GI tract, epithelium and other cells, and on the natural microflora
Bioavailability and metabolism of nanosizedmaterials compared to macroscale equivalents
Occupational exposure issues during production of nanomaterial-containing products
Environmental exposure and ecotoxicity
Managing UncertaintyResearch Needs for Safety Assessments
• Test substances need to be well-characterized• Realistic dose levels • Exposure routes need to be appropriate• Battery of screening tests for nanomaterials should
be developed• Obtain pharmacokinetic data when possible• Chronic studies needed• Standardized methods for measuring exposure levels
are necessary• More studies!
Carbon Nanotubes, Bayer
Managing Uncertainty Conclusions
To date, nanomaterials have not generated any known human or environmental health problems
Toxicological studies need to be conducted and results evaluated in the context of expected exposure before making any conclusions regarding the safety of any nanomaterial
Essential to consider both hazard and exposure potential when characterizing risks
Important to implement protective measures in the face of uncertainty for some nanoscale materials
Managing Uncertainty
