Introduction to occupational (industrial) toxicology

Gunnar Damgård NielsenPhD, Dr Sc (pharm)

National Research Centre for the WorkingEnvironment

gdn@nrcwe.dk

Updated: 3.09.2014

Occupational diseases and predictive toxicological tests

Poison•Toxikon: Greek word for bow (arrow poison)•Toxicum: Roman word for poison•Toxin: English, for a toxic naturally occurring compound.•Toxicology is the science of poison (adverse effects on living systems). Toxicity describes the nature of an adverse effect. •Paracelsus (1493-1541): Dosis sola facit veneum/the dose alone makes a poison

Bingham E, Zapp J. Industrial toxicology: origins and trends. In: Patty’s Toxicology, fifth ed, vol. 1. John Wiley & Sons, 2001, pp 1-16.

Worker protection (industrial health) - an interdisciplinary approach

Occupational medicine (symptoms, diseases and diagnosis)(Diseases from dust (asbestos, quartz, cotton), metals (beryllium, cadmium, lead, manganese, mercury) and carcinogenic compounds (benzene, chromates, aromatic amines, and vinyl chloride)

Hippocrates (~400 BC; e.g. metals), Galen (~150 AD; mines and acid mists), Paracelsus (~1500; Monograph on miners disease), Ramazzini (~1700; father of occupational medicine),Pott (~1750; scrotal cancer in young chimney sweeps)Occupational hygiene (exposures assessment and preventive measures) (substitution, enclosure, ventilation,personal sampling)Occupational toxicology (predictive testing) (short-term and long-term animal studies; biological monitoring) Epidemiology (prevalence and incidence)●Gochfeld M. Chronologic history of occupational medicine. J Occup Environ Med 2005; 47: 96-114.●Nielsen and Øvrebø. Background, approaches and recent trends for setting health-basedoccupational exposure limits: a minireview. Regul Toxicol Pharmacol 2008, 51, 253-269.

Development of industrial toxicology

At World War I, about 3000 to 4000 compounds were studied for acute toxicity for chemical warfare purposes, including phosgene (COCl2) and bis(β-chloroethyl) sulfide).

By the midt-1930s, large chemical companies established toxicologicalLaboratories, for example, DuPont, Dow and Union Carbide. In the US grants for industrial toxicology were given to US universities, for example, Harvard, University of Pittsburgh, New York University, University of Cincinnati and Johns Hopkins University.

In 1949, the US FDA proposed procedures for 2-year studies in rats and1-year studies in non-rodents as dogs.

In 1959, the US FDA proposed a protocol for “lifetime” test with rats. The FDAalso proposed a protocol for the three-generation reproductive study.

Society of Toxicology (1960) for industrial toxicologists in the US.

Bingham E, Zapp J. Industrial toxicology: origins and trends. In: Patty’s Toxicology, fifth ed, vol. 1. John Wiley & Sons, 2001, pp 1-16.

Acute toxicity is still an issue in occupational toxicology

Example:Organophosphate pesticides (acute toxicity and delayed polyneuropathy)

Phosgene (COCl2), ozone, nitrogen dioxide, causing lung oedema.

CO, H2S (both blocking of appropriate oxygen supply)

Very high exposures to airway irritants (e.g.Cl2, CH3COOH, HCl, dust from World Trade Center) can cause Reactive airways dysfunction syndrome, RADS)

Insecticides Isocyanates for polyurethane Manure: H2S Alkaline dust

Examples of newer acute studies

• Spray products interfere with lung surfactants

• Sensory irritation

• Organophosphate pesticides

Neuronal Cells

Illustration af neutron

Anticholinesterase organophosphates (OP): insecticides and chemical warfare agents

Active compound

Acetylcholinesterase (AChE)

Irreversible inhibition

General scheme for all OP

Can be hydrolysed or may proceed to irreversible inhibition (aging)

Neuropathy target esterase (NTE)

AChE: acute toxicity

NTE: delayed neurotoxcity

Costa LG. Current issue in organophosphate toxicity. Clin Chim Acta 2006, 366, 1-13.

Bladan

Tri ortho cresyl phosphate in ratsEnlarged dystrophic axons in the terminal (medullary) levels of the gracile fasciculus

Jortner et al. Neuropathological studies of rats following multiple exposures to tri-ortho-tolyl phosphate, chlorpyrifos and stress. Toxicol Pathol 2005; 33: 378-385

Tri-ortho-cresyl phosphate: delayed neuropathy

Diseases:• Adulterated for Jamaica ginger (1920): • Adulterated cooking oil (many thousands)• Pilots at risk?

Risk assessment can benefit from predictive toxicology and a relevant exposure assessment

Pesticides give rise to public health concern

• Both occupational herbicide and occupational insecticide exposure were significantly associated with Parkinson’s disease; 28 cross-sectional studies and 1 cohort study –exposure assessment were based on exposure-history a)

- potential bias: recall bias and past exposure? • Public exposures to pesticides were not associated with

any significant health risk (HI << 1) and the cancer risk was negligible (about 10-7 for infants) b) - potential limitations: only inhalation; high body burden due to dermal uptake and food

• Only new prospective studies with appropriate exposure assessments are informative a)

a) Allen MT and Levy LS. Parkinson’s disease and pesticide exposure – a new assessment. Crit Rev Toxicol 2013: 43: 515-534.

b) Yusà et al. New screening approach for risk assessment of pesticides in ambient air. Atmos Environ 2014; 96: 322-330.

Most occupational diseases are due to repeated exposures

Occupational exposure routes and classical endpoints. Effects often due to high exposuresSkin and eyes

a) Local effects (e.g. irritation, necrosis and contact sensitisation)b) Systemic effects after skin contact include absorption and internal organ effects

Inhalationa) Local effects on the respiratory tract (e.g. irritation, asthma, COPD, pneumoconiosis and cancer)b) Systemic effects after absorption (e.g. on the CNS, liver, kidney, cardiovascular system and cancer)

Beckett WS. Occupational respiratory diseases. N Eng J Med 2000; 342: 406-413.Sing N, Davis GS. Review. Occupational and environmental lung disease. Curr Opin Pulm Med 2002; 8: 117-125.

Skin irritation

Ambienttemperature

Humidity/environment

Mechanicalstress

Chemicals:SufactantsSolventsAcidsBasesOxidizing agents

Radiation

Stratum corneumdamages: barrier

dysfunction

•Pruritus•Inflammation

Functio laesa (dysfunction)Dolor (pain)Tumor (swelling)Rubor (redness)Calor (heat)

Fluhr et al. Skin irritation and sensitization: mechanisms and newApproaches for risk assessment. Skin Pharmacol Physiol 2008,21, 124-135

Allergic contact dermatitis

Skin sensitizers E.g. fragrances, preservatives, rubber chemicals, industrialepoxy resins, acrylates, medicaments, chromates and nickel

Reacts (haptenation) with skin proteins

Activation of the immune system

Danger signal

Skin sensitization

Allergic contactdermatitis

New exposure

(Delayed T-cell-mediatedResponse)

Nickel allergy

Basketter et al. Skin irritation and sensitization: mechanisms and new approaches for risk assessment. Skin Pharmacol Physiol 2008, 21, 191-202.

Validated in vivo predictive testsSkin irritation•Draize rabbit skin test

Allergic contact dermatitis•Guinea pig maximization test (adjuvant test)•Buehler occluded patch test (repeated applicationon guinea pigs)•Local lymph node assay (application on mouse earsand measurement of proliferation in the local lymphnode

Fluhr et al. Skin irritation and sensitization: mechanisms and new Approaches for risk assessment. Skin Pharmacol Physiol 2008,21, 124-135.

Basketter et al. Skin irritation and sensitization: mechanisms and new approaches for risk assessment. Skin Pharmacol Physiol 2008, 21, 191-202.

Important occupational lung diseases

1. Asthma2. Chronic obstructive pulmonary disease3. Pneumoconioses 4. Cancer in the airways

Hoffmeyer et al. Pneumokoniosen. Pneumologie 2007, 61, 774-797

Work-related asthma (WRA)

•Occupational (de novo) asthma (OA)• Caused by sensitizers• Irritant induced•Work-exacerbated (of pre-existing) asthma (WEA)Occupational asthma (OA) has been defined as a disorder characterized by variable airflow limitation, airway hyper-responsiveness, and airway inflammation due to a particular occupational environment and not to stimuli outside the workplace

Smith and Bernstein. Management of work-related asthma J Allergy Clin Immonol 2009, 123, 551-557.Dykewics MS. Occupational asthma: current concepts in pathogenesis, diagnosis, and Management. J Allergy Clin Immunol 2009, 123, 519-528.

1. Asthma

Illustration af anatomien ved et astmaanfald

Se fx EncyclopædiaBritannica.

Sensitizers causing occupational asthma

Experimentalanimals

Molds Latex gloves Wheat flour Wood dust

IgE from proteins (diagnosis from IgE in human serum):

Low molecular weight compounds

Dykewicz MS. Occupational asthma: current concepts in pathogenesis, diagnosis, and management,. J Allergy Clin Immunol 2009, 123, 519-528.

For example: acid anhydrides, acrylates,polyisocyanates.

Diagnosis in humans by provocationAppropriate animal models???

2. Chronic obstructive pulmonary disease due to emphysema

•Emphysematous lung destruction reduces maximum expiratory flow by decreasing the elastic recoil force available to drive air out of the lungs

•Emphysema is characterized by dilatation and destruction of lung tissue beyond the terminal bronchioles

Hogg JC. Pathophysiology of airflow limitation in chronic obstructive pulmonary disease. Lancet 2004, 364, 709-21.Boschetto P, Quintavalle S, Miotto D, Cascio NL, Zeni E, Mapp CE. Chronic obstructive pulmonary disease (COPD) and occupational exposures. J Occup Med Toxicol 2006, 1: 11.

Smoking Coal dust Silica dust

Centrilobular emphysema (CLE)

Hogg JC. Pathophysiology of airflow limitation in chronic obstructive pulmonary disease. Lancet 2004, 364, 709-21

Smoke induced emphysema

Normal lung

Appropriate models?

3. Pneumoconioses a,b)

Dust induced interstitial lung diseases causing functional changes. Symptoms: breathlessness and cough

• Asbestos: asbestosis• Crystalline silica (SiO2)*: silicosis• Dust from coal mining: coal workers’

pneumoconiosis

Pneumoconioses with prominent interstitial fibrosis (“malignant fibrosis”)

a) Hoffmeyer et al. Pneumokoniosen. Pneumologie 2007, 61, 774-797b) Rees and Murray. Silica, silicosis and tuberculosis. Int J Tuberc Lung Dis 2007, 11, 474-484.c) Brüske et al. Respirable quartz dust exposure and airway obstruction: a systematic review and meta-analysis. Occup Environ Med 2014; 71: 583-589.

*•About 300 studies in 2014c): Do we need new studies?•If we need new studies, what type of questions should they address, would they be fulfilled by human or animal studies and what type of methods could be used?

Silicosis (in general >10-20y of exposure)

Whole lung section with chronic silicosis. Small circumscribed nodules are seen in the upper zone

Silicotic nodule with a central zone of hyalinisedcollagen with a whorledappearance and peripheraldust-containing macrophages

Massive opacity (nodulus) in the right upper zone of the lung.

Hoffmeyer et al. Pneumokoniosen. Pneumologie 2007, 61, 774-797Rees and Murray. Silica, silicosis and tuberculosis. Int J Tuberc Lung Dis 2007, 11, 474-484.

Results from a rat model:

2 mg quartz (DQ12) were intratracheally instilled. Lungs and bronchoalveolar lavage fluid were

collected seven days (7d) following the instillation

Albrecht et al. The crucial role of particle surface reactivity in respirable Quartz-induced reactivity oxygen/nitrogen species formation andAPE/Ref-l induction in rat lung. Respiratory Research 2005, 6:129

Lung from a control rat Lung from an exposed rat

Inflammation 7d after 2 mg DQ12 i.t. administered in rats

No validated animal model. Are our models sufficient?

Se illustration fra artiklen forrige side

Crystalline silica can induce many different effects

• Pneumoconiosis• Chronic bronchitis• Emphysema• Mineral dust airway disease• Increase infection (TB)• Lung cancer• Autoimmune diseases• Renal disease

In general, all compounds may induce many different diseases!

Rees and Murray. Silica, silicosis and tuberculosis. Int J Tuberc Lung Dis 2007, 11, 474-484.

Study in the German porcelain industry; NOAEL for decrease in lung function at 0.25 mg/m3

Human lung carcinogensa)

o Asbestoso Chrystaline silica (quarts)o Chromium (VI)o Cadmiumo Nickelo Arsenico Berylliumo Tobacco smokeo Polycyclic aromatic hydrocarbons (e.g. soot

and tar)

a) Beckett WS. Occupational respiratory diseases. N Engl J Med 2000, 342: 406-413

By far, the majority of carcinogenic compounds have been discovered in long-term animal studies

4. Cancer in the respiratory system. Asbestos, an example of cancer-inducing fibres

Serpentine:Chrysotile (white)

Amphibole:Amosite(brown)

Amphibole:Crocidolite(blue)

Becklake MR, Bagatin E, Neder JA. Asbestos-related diseases of the lungs and pleura: uses, trends and management over the last century. Int J Tuberc Lung Dis 2007, 11, 356-369.

Hagemeyer O, Otten H, Kraus T. Asbestos consumption, asbestos exposure and asbestos-related occupational Diseases in Germany. Int Arch Occup Environ Health 2006, 79, 613-620.

Asbestos

Non-malignant: pleural plaques (often calcified, in the parietal plaura [lines the chest wall and the surface of the diaphragm])

Malignant: mesothelioma (pleura or peritoneum)

Non-malignant: asbestosis (peribronchiolar fibrosis/scarring).

Malignant: laryngeal cancer and lung cancer.

Hagemeyer O, Otten H, Kraus T. Asbestos consumption, asbestos exposure and asbestos-related occupational Diseases in Germany. Int Acch Occup Environ Health 2006, 79, 613-620.

MesotheliomaLung cancer

Se illustrationer af dette via søgning på internettet

Toxicological approaches to evaluation of fibres (3Ds)

Life-long inhalation studies in mice and rats (dose (D)

Physical/mineralogical properties (e.g. Dimensions (D), durability (D), break down products and surface properties)

The purpose of predictive toxicology is to prevent outbreak of diseases. Types

of test for toxicity

• Acute toxicity• Skin, eye and airway irritation, and

corrosivity• Sensitization• Repeated dose toxicity • Reproductive toxicity• Genotoxicity• Carcinogenicity

Key referencesBasketter D, Darlenski R, Fluhr JW. Skin irritation and sensitization: mechanisms and new approaches for risk assessment. Skin Pharmacol Physiol 2008, 21, 191-202.

Beckett WS. Current concepts: Occupational respiratory diseases. N Engl J Med 2000; 342: 406-413.

Becklake MR, Bagatin E, Neder JA. Asbestos-related diseases of the lungs and pleura: uses, trends and management over the last century. Int J Tuberc Lung Dis 2007, 11, 356-369.

Costa LG. Current issue in organophosphate toxicity. Clin Chim Acta 2006, 366, 1-13.

Dykewics MS. Occupational asthma: current concepts in pathogenesis, diagnosis, and Management. J Allergy Clin Immunol 2009, 123, 519-528.

Fluhr JW, Darlenski R, Angelova-Fischer I, Tsankov N, Basletter D. Skin irritation and sensitization: mechanisms and new Approaches for risk assessment. Skin Pharmacol Physiol 2008,21, 124-135.

Hogg JC. Pathophysiology of airflow limitation in chronic obstructive pulmonary disease. Lancet 2004, 364, 709-21.

Rees D, Murray J. Silica, silicosis and tuberculosis. Int J Tuberc Lung Dis 2007, 11, 474-484.

Singh N, Davis GS. Review. Occupational and environmental lung disease. Curr Opin Pulm Med 2002; 8: 117-125.