What are the toxicological impacts of surface coatings/surface - - PowerPoint PPT Presentation

What are the toxicological impacts of surface coatings/surface treatments on TiO2 particles?

David B Warheit and Scott Brown, Chemours Company

Predominant Organic and Inorganic Surface Modifications for TiO2 in Commerce

TiO2 Inorganic Surface Modifications

Impact of Hydrophobic Organic Coatings

Study Design and Particle Information for Rehn et al.

Studies to Assess Pulmonary Hazards to Particulates

Pulmonary Bioassay Studies

1)Rigorous physicochemical characterization of particle-types 2)Dose response characteristics 3)Time course experimental protocol 4)Utilization of benchmark particulate controls (positive and/or negative)

Pulmonary Bioassay Components

Bronchoalveolar Lavage Assessments

Lung Inflammation & Cytotoxicity

• Cell Differential Analysis
• BAL Fluid Lactate Dehydrogenase (cytotoxicity)
• BAL Fluid Alkaline Phosphatase (epithelial cell toxicity)
• BAL Fluid Protein (lung permeability)

Lung Tissue Analysis

• Lung Weights
• Lung Cell Proliferation (BrdU)
• Parenchymal
• Airway
• Lung Histopathology

Warheit et al 2003

Neutrophils Return to Normal Levels Post Exposure (PE)

EHP Draft Warheit et al 1-22-2018.docx - _Hlk504415986

LDH Rise is Fully Reversible

No Impact on Histopathology

10mg/kg OTES TiO2 + Tween 80 Saline Control

OECD / Creutzenberg et al. 2013

Warheit et al. 2006

Reversible for TiO2, Progressive for Quartz

Normal Proliferation for TiO2

Warheit et

• al. 2005

Lung Tissue Section of Rat after 28 day (4 wk) exposure to 1300 mg/m3 TiO2 III

(High Surface area , Alumina & Silica coated TiO2) Thick Arrows  thickenced aveolar walls Thin Arrows  normal alveolar walls A=Alveolus (H&E Stain)

EHP Draft Warheit et al 1-22-2018.docx - _Hlk504415986

% Neutrophils Return to Normal Levels for all TiO2

Warheit et al. 2007

Characterization of Ultrafine TiO2 Particle-types

Sample Crystalline phase Median size and width distribution (nm) Surface

area (m2/g) pH Chemical reactivity

in water* in PBS deionized water in PBS delta b*

F-1 rutile

382.0 ± 36%

2667.2 ± 35%

5.8 7.49 6.75 0.4

uf-1 rutile

136.0 ± 35%

2144.3 ± 45%

18.2 5.64 6.78 10.1

uf-2 rutile

149.4 ± 50%

2890.7 ± 31%

35.7 7.14 6.78 1.2

uf-3

80/20

anatase/ rutile

129.4 ± 44%

2691.7 ± 31%

53.0 3.28 6.70 23.8

uf-3

C 300 nm

uf-2

B 300 nm

uf-1

A 300 nm

Properties of TiO2 particles is related to application/function

• Crystal structure/composition: Anatase vs. Rutile vs. 80% Anatase: 20%

Rutile crystallinity

• Neutralization of particle surface vs. “uncoated” surface
• Surface coatings – alumina – amorphous silica
• “catalysts” are very different from “pigments” from a physicochemical
• charac. standpoint– but both are identified as titanium dioxide
• Catalysis and photocatalysis favor enhanced “surface reactivity” effects

Pulmonary Inflammation

BAL Fluid LDH Values (cytotoxicity)

BAL Fluid Micro Protein Values (permeability)

Pulmonary Cell Proliferation Rates

Lung Sections of Rats exposed to uf-1 (A); uf-2 (B); or F-1 (C)- 3 months pe

Lung Section of Rat exposed to uf-3 3 months postexposure

Lung Section of Rat exposed to Quartz particles - 3 months postexposure

ACUTE AND SUBCHRONIC ORAL TOXICITY STUDIES IN RATS WITH NANOSCALE AND PIGMENT GRADE TITANIUM DIOXIDE PARTICLES [FOOD CHEM TOX 2015]

30

3 Studies:

Transmission Electron Microscopy (TEM) Images and Sample Types for the Three Test Substances

Physicochemical Characterization of Test Particles

Comparative Mass and Number Percent Data and Diameter Type Derived from XSDC

Representative % Material under 100nm

Mean Body Weights of Male & Female Rats 90-day Study

35

Parameters measured in 90-day Study that were not different from Controls

• Oral Exposures to 0, 100, 300 or 1000 mg/kg bw/day
• Male/Female Body weights from 90-day study
• Summary of Clinical Chemistry Values for Male Rats
• Summary of Clinical Chemistry Values for Female Rats
• Mean Absolute and Relative Organ Weights in Male Rats
• Mean Absolute and Relative Organ Weights in Female Rats
• Mean Daily Food Consumption by Male Rats
• Mean Daily Food Consumption by Female Rats
• Mean Daily Food Efficiency of Male Rats
• Mean Daily Food Efficiency of Female Rats
• Gross, Anatomic or Microscopic Pathology of all of the organs

36

• Characterized by the presence of TiO2 particles within the digestive tract,

draining lymphoid tissue and nose without evidence of an adverse tissue response to titanium dioxide.

• The test substance generally appeared as granular brown aggregates or

clumps on H&E staining.

• The substance was most abundant and most consistently observed in the

lumen and along the mucosal surface of the cecum.

Test substance-related microscopic findings

Mean Body Weights of Male Rats 28-day Study

Title of Presentation

Parameters measured in 28-day Study that were not different from Controls

• Oral Exposures to 24,000 mg/kg bw/day – Male Rats
• Body weights from 28-day study
• Summary of Clinical Chemistry Values for Male Rats
• Mean Absolute and Relative Organ Weights in Male Rats
• Mean Daily Food Consumption by Male Rats
• Mean Daily Food Efficiency of Male Rats
• Gross, Anatomic or Microscopic Pathology of all of the organs

39

Summary Table for Oral Toxicity Studies following exposures to Pigmentary or Nanoscale TiO2 Particles

40

*parameters tested included clinical pathology, gross, anatomic & microscopic pathology included all organs, in life measures – including body wts, food consumption and food efficiency

Summary

Summary (contd.)

Toxicogenomic analysis of mouse lung response following exposure to titanium dioxide nanomaterials reveal their disease potential at high doses Luna Rathman et al. ,Mutagenesis 2017 32 59-76 C57BL/6 mice were exposed to six individual size, crystal structures and surface modifications (hydrophobic or hydrophilic) to investigate whether the mechanisms leading to TiO2 NP- induced lung inflammation are property specific. While the particle size clearly influence the overall acute lung responses, a combination of small size, crystalline structure and hydrophilic surface contributed to the long-pathologic effects

• bserved a the highest dose

Categorization of nano-structured titanium dioxide according to physicochemical characteristics and pulmonary toxicity Naoki Hashizume et al., Toxicology Reports 3 (2016) 490 – 500 In the present study, we conducted intratracheal instillation studies in rats to clarify the associations between the physicochemical characteristics of seven characterized forms of TiO2 and the pulmonary inflammatory responses… TiO2 particles coated with Al (OH)3 induced a greater pulmonary inflammatory response than did non- coated particles