### February 15, 2012



# TOXICOLOGY AND 

# MEDICAL

Cynthia Graham, PhD


### Huntsman2 

# Objectives

Toxicology

• To discuss the importance of physical

- chemical properties

• To provide an overview of new toxicology data for diisocyanates,

• To provide additional sources for information.



## Medical

• To explain how exposure relates to development of symptoms



### • To explain medical surveillance recommendations.

# TOXICOLOGY4 

# Major Factors Affecting 

# Diisocyanate Toxicity Testing

Physical and Chemical Properties Hydrophobic

• P romotes a non

- homogeneous reaction favoring formation of polyurea


### Electrophilic

• Reactivity prefers nucleophiles containing

– NH and

– SH over

– OH groups

• Thus reactions with endogenous macromolecules preferred over hydrolysis


### Vapor & Aerosol

• Chemical reactivity of diisocyanates results in principally nasals lesions with vapor and pulmonary lesions with aerosols in experimental animals5 

# Particle Size is Important

Aerodynamic Diameter [μm] 0 20 40 60 80 100 120 140 160 180 200 0.2 0.4 0.6 0.8 1.0 1.2



### • Respirable MDI particles are difficult to generate

• The black curve is a laboratory generated atmosphere used in a LC 50 

### study. The red curve reflects workplace 

### spray particles6 

# Major Factors Affecting 

# Diisocyanate Toxicity Testing

Consideration of these factors is critical for

• Designing toxicology studies



## • Interpreting toxicology data

• Using the resulting data for Risk Assessments7 

# Diisocyanates Have a Substantial 

# Toxicity Database

• Acute Oral, Dermal and Inhalation Toxicity

• Irritation

• Eye , skin, sensory (RD 50 )



### • Sensitization

• Skin and Respiratory



### • Repeated Dose Toxicity

• Reproductive Toxicity

• Developmental Toxicity

• Mutagenicity

• Carcinogenicity

• Absorption and Metabolism

(See Appendix for more details)8 

# New Information

• Threshold of Respiratory Sensitization

• Biochemistry and Biomonitoring



# • TDI Carcinogenicity9 

# Threshold of Respiratory 

# Sensitization

• BN rat model (MDI)

• 5

- day inhalation (induction) exposure (various Conc. X Time)

• four 30

- min inhalation challenges to 40 mg MDI /m3 on target days 20, 25, 50, and 65.

• Exposure aerosols size (MMAD 1.5

- 1.9~m, GSD 1.6

- 1.9).

• Endpoints

• BAL

- neutrophils and

• physiological measurements

- changes in breathing patterns delayed in onset

• 2 nd protocol had 4 th challenge at a dose escalation

• Elicitation threshold of 5 mg MDI

- aerosol/m 3 at a 30 min challenge duration

• Short high

- level exposure patterns appear to bear a higher sensitizing potency than equal „Conc. x Time‟ products at longer exposure periods Reference: Pauluhn J and Poole A. 201110 

# Biochemistry & Biomonitoring

Mechanism of transfer of TDI from air to serum albumin

• Wisnewski, AV, JM Hettick and PD Siegel. Toluene diisocyanate reactivity with glutathione across a vapor/liquid interface and subsequent transcarbamoylation of human albumin. Chem. Res. Toxicol. (2011) 24: 1686

- 1693.

TDI

- albumin adducts based on TDI

- peptide analysis

• Hettick, JM and PD Siegel. Determination of the toluene diisocyanate binding sites on human serum albumin by tandem mass spectrometry. Anal. Biochem. (2011) 414(2): 232

- 238.

TDI

- albumin adducts based on TDI

- amino acid analysis

• Sabbioni, G., Q. Gu and LR Vanimireddy. Determination of isocyanate specific albumin

- adducts in workers exposed to toluene diisocyanates. Biomarkers (2012) [Epub ahead of print]11 

# TDI Carcinogenicity

• NTP / IARC cancer classifications

- Based on oral (gavage) exposure to TDI (80/20)  rodent tumors, except male mice (NTP, 1986).

• Comparable tumor responses seen after oral (feed) exposure to 2,4

- TDA  rodent tumors, except male mice (NTP, 1979)

• Statistical analysis of TDI and TDA tumors reported by NTP consistent with 5% of TDI dose being converted to TDA prior to and/or post

- dosing (Sielken et al., 2012)

• Atypical formation of TDA in NTP TDI study is chemically and biologically plausible due to flawed TDI handling (allowed TDI conversion to TDA) and exposure protocol (stomach acid)

• Contention that TDA is not formed under typical exposures (in presence of macromolecules at neutral pH) is consistent with:

• Inhalation of TDI at MTD (0.15 ppm)  no rodent tumors (Loeser, 1983)

• Inhalation of TDI (2 ppm)  no free TDA in rats (Timchalk et al., 1994)

• Occupational TDI exposures  no human cancers or free TDA in urine/blood12 

# For More Information

• Pauluhn J and Poole A. 2011. Brown Norway rat asthma model of diphenylmethane

- 4,4'

- diisocyanate (MDI): Determination of the elicitation threshold concentration of after inhalation sensitization. Toxicology. 281:15

- 24

• Sielken R., 2012. Statistical comparison of carcinogenic effects and dose

- response relationships in rats and mice for 2,4

- toluenediamine to those ascribed to toluene diisocyanate. Hum. Ecol. Risk. Assess. (in press).

• MDI & TDI: Safety, Health and the Environment . A Source Book and Practical Guide . Eds. D.C. Allport , D. S. Gilbert and S. M. Otterside , Published by John Wiley & Sons, Ltd., 2003.



### • www.polyurethane.org

• Center for the Polyurethanes Industry



### • http://dii.americanchemistry.com

• American Chemistry Council Diisocyanates Panel

# MEDICAL14 

# Medical

- Overview

• To explain how exposure relates to development of symptoms



## • To explain medical surveillance recommendations15 

# Possible Adverse Health Effects

Possible Effects on Respiratory System:

• Occupational Asthma

o Sensitization may occur after a single, extreme overexposure or repeated overexposure

o Symptoms may not appear at initial exposure, but after several weeks and a subsequent exposure

• Upper Respiratory Tract Irritant (MDI, TDI)

o Irritating effects are generally associated with spills and/or process upset conditions

• Hypersensitivity Pneumonitis (HP)

o Low prevalence with diisocyanates (Vandenplas O, et al. 1993)

• Reactive Airways Dysfunction Syndrome (RADS)

o After an acute, single exposure to a high level of an irritant16 

# Possible Adverse Health Effects

Occupational Asthma Prevalence

• Diisocyanates are listed among the most common suspected causal agents in population

- based occupational surveillance systems

.

• “ISO and N

- ISO claims declined from the previous period, especially for ISO, perhaps because of effective surveillance programs .”
( Buyantseva L, Tarlo SM, et al. 2011)

• Incidence rates range from 0 to 1.5% per year with a cumulative incidence of 4% after 5 years , according to one study

.

• Increased incidence found in the first 2 years of employment and with certain job activities

• Risk declines with decrease in exposure17 

# Prognosis for Diisocyanate



# Sensitized Subjects

Good outcome and prognosis when :

• Diagnosed early

• Complete removal from further exposure

• Improvement or complete recovery is seen in 50

- 80% of those subjects removed from exposure



### Prognosis is poor when subjects are not removed from the exposure setting.

• Symptoms usually persist and can become worse

• Permanent lung damage may occur

• Asthma deaths have been reported18 

# Worker Medical Surveillance

Purpose :

• To establish a baseline prior to diisocyanate exposure

.

• To evaluate employees for upper or lower respiratory irritation or sensitization , and contact dermatitis

.

• To ascertain whether any conditions have been caused by, or will be aggravated by, diisocyanate exposure

.

• Check for Non

- Specific Bronchial Hyperreactivity (NSBR)

• May be important risk factor for symptom development
, can result in misclassification of occupational asthma

• Asthmatics may have increased symptoms and 

### clinical findings with diisocyanate exposure

.19 

# Worker Medical Surveillance

Suggested Frequency

• Pre

- placement screening

• Annual periodic examinations

• Return to work examinations

• Absence due to cardiac or respiratory illness

• Following accidental exposure to diisocyanates

• When diisocyanate workers experience recurrent respiratory symptoms ( which may be work related )20 

# Diagnosis of Occupational Asthma

Important to diagnose early and accurately to prevent chronic disability 

### Diagnosis can usually be made by use of the following :

• History and physical
,

• Measurement of serial Peak Expiratory Flow Rate (PEFR), with and without exposure ,

• Measurement of serial, shift

- related spirometry, preferably 

### performed concurrently with PEFR monitoring, and

• Methacholine challenge.

• Specific Bronchial Inhalation Challenge

– Gold Standard

– Not widely available21 

# DII

- NIOSH TDI Research Study

• Joint research effort between ACC DII Panel and NIOSH, also have union representation

• Study Focus: Potential risk of asthma associated with occupational exposure to TDI at US manufacturing plants

• All eligible TDI production workers were asked to participate

• Study addresses three discrete areas:

• Medical monitoring of workers identified as working with diisocyanates,

• Exposure assessment to characterize jobs and specific tasks with regard to their risk for exposure to TDI, and

• Medical assessment of asthma22 

# Current Status

• Two plants remain in the study including Bayer Baytown and BASF Geismar

• A redesign of the study was implemented in Q2 2011 to utilize web

- based technology to improve data collection

• Data collection will continue until June 2012 for a five

- year research study

• Data analysis plan in development

• Study could provide additional information for medical diagnosis guidelines

• Target is to publish findings in an appropriate peer

- reviewed journal23 

# ACOEM* Respiratory Practices 

# Guidelines

• Previous guidelines directed toward Injury
care

• Update to address diagnosis of airway disorders (asthma) and parenchymal 

## ( pneumoconioses )

• Objectives

– Improve Consistency

– Reduce Variability

– Follow Hierarchy of Evidence

– Improve Effectiveness



# * American College of Occupational and Environmental Medicine24 

# Dimension of Evidence Based 

# Guidelines in Occupational Asthma

• Diagnosis and testing

• Work Relatedness

• Treatment



## • Disability Management and Return to Work

– Intended to ensure that to the greatest extent possible, medical decisions, are based

on and consistent with good evidence of effectiveness and benefit.25 

# Resources

• Vandenplas O, et al. 1993. Occupational asthma and extrinsic alveolitis due to isocyanates: current status and perspectives. B J Ind. Med. 50:213

- 228

• Buyantseva L, Tarlo SM, et al. 2011. Reduction in Diisocyanate and Non

- Diisocyanate Sensitizer

- Induced Occupational Asthma in Ontario. JOEM.

• Bernstein, D.I. 1998. A Guide for the Primary Care Physician in Evaluating Diisocyanate

• Bernstein, D.I. & Jolly, A. 1999. Current diagnostic methods for diisocyanate induced occupational asthma. Am J Ind Med. 36:459

- 468.

• Klees, J.E. & Ott, M.G. 1999. Diisocyanates in Polyurethane Plastics Applications. Occup Med. 14 (4): 1

- 18.

• National Institute for Occupational Safety and Health (NIOSH). 1996. NIOSH Alert: Request for assistance in preventing asthma and death from diisocyanate exposure. DHHS (NIOSH) Publication No. 96

- 111.

# APPENDIX

# TOXICOLOGY28 

# Acute Toxicity

Test substance Oral LD 50

(mg/kg bw) Dermal LD 50

(mg/kg bw) Inhalation

LC 50 (mg/m 3 ) Inhalation

RD 50 (mg/m 3 )

rats rabbits Rats (4 hr) mice

4,4’

- MDI 2240 (1 hr)

PMDI >15,800 >7900 490 32 (4 hrs)

TDI 80:20 4130 >10,000 101 2.8 (4 hrs)

2,4

- TDI 5800 69 1.4 (3 hrs)

2,6

- TDI 4130 1.9 (3 hrs )

1) The lower the number, the higher the toxicity 2) Diisocyanates more toxic via inhalation; 3) Differential toxicity of monomer vs. polyisocyanate29 

# Irritation and Sensitization

Test Substance Irritation (eye or skin) Sensitization (Skin & respiratory)

MDI mild to moderate positive

PMDI mild to moderate positive

TDI Moderate to severe positive30 

# Repeated Inhalation Exposures 

# Portal

- of

- Entry Toxicity

MDI PMDI

Exposure scenario 17 hrs/day 5days/week 3 months 6 hrs/day 5days/week 1

- 2 years Levels (mg/m 3 ) 0, 0.3, 1.0, 3.0 0, 0.2, 1.0, 6.0

Species rats rats

Histo

- pathology Nasal and pulmonary tissue lesions (12

- 20 month data unavailable) Nasal and pulmonary tissue lesions

NOAEL 0.3 mg/m 3 0.2 mg/m 3

NOAEL : No observed adverse effect level31 

# Reproductive Toxicity

• No damage to the reproductive organs was found with nearly lifetime inhalation exposure of rats to TDI

• 2

- generation inhalation study with 80/20 TDI

– No TDI

- related effects were seen in any reproductive parameters (tested up to 300 ppb)

– MDI is expected to have similar effects as TDI32 

# Developmental Toxicity

• Studies designed to assess toxicity to the developing fetus including teratogenesis (malformations)

• Developmental toxicity studies (inhalation exposures) 

### have been conducted with MDI, PMDI and TDI

– No indication of toxicity to the developing fetus or to the new

born, in the absence of maternal toxicity

– No evidence of teratology



### • Diisocyanates do not show a potential for developmental toxicity or teratogenicity33 

# Carcinogenicity Studies

TDI TDI MDI PMDI

Oral, in corn oil Inhalation

vapor Inhalation

particulates Inhalation

particulates

rats & mice rats & mice rats (female) rats (mg/kg bw) 0, 60, 120 (f r/m) † 0, 30, 60 (mr) 0, 120

- 140 (mm) (mg/m 3 )

0, 0.4, 1.1 (mg/m 3 )

0, 0.2, 0.7, 2.0 (mg/m 3 )

0, 0.2, 1.0, 6.0

5 days/week 2 years 6 hr/day

2 years 17 hrs/day

20 months 6 hr/day

2 years

Increased tumors No tumor

increase

over controls Tumors seen at

high

exposure levels Tumors seen at

high

exposure levels
In all cases the Maximum Tolerated Dose (MTD) was achieved or exceeded

† : f r/m: female rat/mouse; mr: male rat; mm: male mouse34 

# Metabolism Study of MDI in Rats

• Inhalation exposure to 3.67 mg/m 3 14 

### C

- MDI for 6h

• Radioactivity distributed to all tissues

• Mainly excreted in feces, remainder in urine & bile; none 

### via exhalation

• Major metabolic pathway following inhalation exposures

• Bioavailable fraction

N

- Acetylation and excretion via bile and urine

• Non

- bioavailable fraction (lung surface, mouth, nares, skin) Polyurea excreted via feces

• No MDA found in urine, bile or feces35 

# MDI Classification in EU

• The EU Member States published the 30th ATP, June 1, 2009.

– Contained revised classification for MDI

- Carcinogen Category 3 (limited evidence of a carcinogenic effect).

– MDI remains labeled as Xn harmful; it was not be re

- labeled as T toxic.

• DSD Category 3 becomes Category 2 under the CLP Regulation.

– This change is not a stricter classification (Suspected of causing cancer by inhalation)

• Carcinogenicity studies:

– High concentrations of specially prepared aerosols respirable: having an aerodynamic diameter of ≤ 10 μm

– The concentration required to cause tumors in the lungs of the test animals was 6mg/m3, which is more than 100

- times the MAK

- value (0.05mg/m3).

– Only a few of the animals showed the formation of benign (likely from recurrent tissue irritation/inflammation)

• Aerosols emerging under practical working conditions are not expected to cause an increased risk for lung cancer

– supported by epidemiological studies. Health surveillance programs involving around 12,000 workers in the MDI processing industry did not show any increased risk of lung cancer.

ISOPA DOCUMENT

# MEDICAL37 

# Possible Adverse Health Effects

Possible Skin Effects

• Irritant

- Irritant contact dermatitis (ICD)

• Sensitizer

- Allergic contact dermatitis (ACD)

– Prevalence

• Handful of reports of ACD due to diisocyanates

• ICD is more common than ACD

• Dermal exposure may result in respiratory sensitization

• Animal studies suggestive

• Inconclusive in humans

Possible Eye Effects

• Irritation (MDI, TDI)

– Irritating effects generally associated with spills and/or process upset conditions38 

# Possible Adverse Health Effects

Possible Effects on Respiratory system:

• Upper Respiratory tract irritant (MDI, TDI)

– Nose
, Throat , and Airways

– Odor threshold is above TLV ( Sense of smell is not protective)

– Irritating effects are generally associated with spills and/or process upset conditions

• Hypersensitivity Pneumonitis (HP)

• Lung tissue disease which presents as flu

- like symptoms , with or without x

ray changes

• Low prevalence with diisocyanates

– Good prognosis with steroid treatmentunless sensitization develops

• Reactive Airways Dysfunction Syndrome (RADS)

– after an acute, single exposure to a high level of an irritant

– Good prognosis with steroid treatmentunless sensitization develops39 

# Possible Adverse Health Effects

Possible Effects on Respiratory System:

• Occupational Asthma

– Clinical Presentation

• Coughing

• Wheezing

• Tightness of chest



### – Symptoms are less severe on week

- ends or after a vacation

– Symptoms will not appear at initial exposure , but after several weeks and a subsequent exposure40 

# Worker Medical Surveillance

Pre

- placement Screening

• Medical Evaluation

• Respiratory and dermal symptom questionnaire

• Medical history



### • Respiratory function tests

• Spirometry (FEV1, FVC)

• Peak Expiratory Flow Rate (PEFR)



### • Medically categorize and assess on a case

- by

- case basis41 

# Worker Medical Surveillance

Periodic Examination

• Medical Symptom Questionnaire

• Targeted to skin and respiratory tract symptoms

• Determine any significant findings or change in symptoms

• Inquire as to possible exposure to diisocyanates



### • Spirometry

• Compare with previous exams

• Measurements provide a means to monitor any changes in airway obstruction.



### • Further physician assessment with findings or symptoms of reversible airways changes.42 

# Diagnostic Algorithm

– 

# The Timeline43 

# Diagnosis of Occupational Asthma

Specific Bronchial Inhalation Challenge ( SBIC)



### • An excellent diagonistic tool , but:

– Potentially dangerous (if not done properly )



### – Not widely available

– Usually not necessary

– Potentially costly
Good History, Physical Exam, Pre



### and Post

- Shift Spirometry, PEFR are Generally Sufficient44 

# Diagnosis of Occupational Asthma

Role of “Diisocyanate

- specific Antibody ” Tests

• No reliable correlation with clinical disease

• Great variability seen among investigators

– Non

- standardized methodology

– Interval from exposure differences



### – Non

- antibody mediated mechanism

• Does not replace physiologic methods for the diagnosis of diisocyanate asthma

.45 

# Basis for Current ACGIH TLV

Lung Function Decrement

MDI

• Exposures below 5 ppb TWA are without effect on FEV1.

• Results are consistent with a lack of effect at < 3 ppb
, but should be interpreted cautiously

.46 

# Basis for Current ACGIH TLV

Lung Function Decrement

TDI

• Exposures below 5 ppb TWA are without effect on FEV1

• Diem Study : Definitive 5 year study on lung effects

.

• Reported loss of lung function in “ high ” vs. “ low ” non

smoker exposure group.



### • Geismar TDI Respiratory Health Study (1967

- 1997)

• No relationship between asthma and cumulative exposure

.

• No lung function effects were seen after transfer out of the TDI unit among work

- related asthma cases.47 

# Epidemiology Studies

Several cohort mortality studies in polyurethane manufacturing

– 40

- year cohort study of TDI polyurethane foam manufacturing in England and Wales:

" unable to link isocyanate exposed employment with risks of lung

cancer or with risks of non

- malignant diseases of the respiratory system. Increased SMR for female lung cancer is most likely caused by factors unrelated to the industry

. " Sorahan & Nichols . 2002. Occ . Environ. Med.

– 37

- year cohort study of TDI polyurethane foam manufacturing in US : "

... no cancer death category showed a strong relation with duration of employment

. " Schnorr et al. 1996. Occ . Environ. Med.

– 29

- year cohort study of TDI & MDI polyurethane foam manufacturing in Sweden :

“ tentative associations...and excess risk... were not supported

. Instead non - significant associations ...were seen." Hagmar et al. 1993. Br. Jrnl Indus. Med.