Occupational Cancer By : Dr. Aliraza Safaiyan M.D. Occupational Medicine Specialist
Introduction Cancer is a leading cause of death worldwide, with 12.7 million new cases and 7.6 million deaths in 2008. Globally, 19% of all cancers are attributable to the environment, including work setting resulting in 1.3 million deaths each year. Occupational carcinogens is important because they are completely preventablee.
The most common cancers associated with occupational exposure: lung and pleura bladder skin laryngeal nasal cavity leukemia throat lymphoma soft-tissue sarcomas liver
Type of Cancer Lung Bladder Mesothelioma Leukemia Laryngeal Skin Cancer (non-melanoma) Sinonasal and nasopharyngeal Kidney Liver Related to Occupational Exposure Estimated % (USA) 6.3 13 % 3 19 % 85-90% (men); 23-90% (women*) 0.8 2.8 % 1-20% (men) 1.5-6% (men) 31-43% (men) 0 2.3 % 0.4-1.1 (vinyl chloride only; men) * In general, the overall attributable risk for mesothelioma in women is 23%. However, if the woman has had "takehome" exposure to asbestos, the risk may be around 90%. "Take home" exposure results from asbestos being carried home on contaminated work clothing or other items.
Risk of developing a particular cancer Personal characteristics such as age, sex, and race Family history of cancer Diet and personal habits such as cigarette smoking and alcohol consumption The presence of certain medical conditions Exposure to cancer-causing agents in the environment Exposure to cancer-causing causing agents in the workplace
Stages in tumor development Initiation (irreversible changes in DNA) Promotion (facilitate tumor development) Progression (development to malignant tumor & Progression (development to malignant tumor & metastases)
Examples (PAH) & (croton oil) in skin cancers in mice (Nitrosamine) & (PCB) in liver tumor in mice Complete carcinogens (cigarette smoke)
Induction-Latency yperiod 3-5 years for radiation or toxin induced Leukemia 20-40 or more asbestos-induced Mesothelioma Solid tumors about 10 12 years For most tumors about 12-25 years
Initiators VS Promoters Initiators Genotoxic Carcinogenic alone Covalently bind to DNA (irreversible) Single exposure (may be) Promoters Not genotoxic Act after initiation Act by cellular proliferation (may be reversible) Repeated exposure required
Prevention Elimination: The most effective means is to ban the carcinogen. (asbestos). Substitution Alternatively, a carcinogenic substance may be substituted with one that is not carcinogenic, or is less hazardous. Engineering controls (expensive, but effective means) for example, ventilation, enclosure or partial enclosure, isolation Administrative controls : job rotation Personal protective equipment (PPE) is the least efficient way of controlling hazardous exposures.
IARC International Agency of Research on Cancers
the IARC classifications Group 1: The agent is carcinogenic to humans. sufficient evidence of carcinogenicity i i in humans. Group 2A: The agent is probably carcinogenic to humans. limited evidence of carcinogenicity in humans and sufficient evidence in experimental animals. Group 2B: The agent is possibly carcinogenic to humans. limited evidence of carcinogenicity in humans and less than sufficient evidence in experimental animals. Group 3: The agent is not classifiable as to its carcinogenicity to humans. the evidence of carcinogenicity is inadequate in humans and inadequate or limited in experimental animals. Group 4: The agent is probably not carcinogenic to humans. there is evidence suggesting lack of carcinogenicity in humans and in experimental animals.
14 IARC Evaluations Dimensions and Groups Types of evidence Human Animal Other - mutagenicity - genotoxicity -metabolism bli -etc. Group 1 Carcinogenic to humans 2A 2B Probably carcinogenic to humans Possibly carcinogenic to humans 3 Not classifiable 4 Not carcinogenic to humans
the IARC classifications Group 1 :63agents, 13 mixtures and 15 exposure circumstances. This includes a number of occupations (eg painter, cabinet maker) as well as different chemicals used primarily in occupational circumstances. group 2A : 31 agents and 3 exposure circumstances are classified. Not all these agents are occupational carcinogens and a review of the IARC classifications i found that 28 agents were definite occupational carcinogens, and a further27 were probable occupational carcinogens
28 definite human occupational carcinogens (IARC group 1); 27 probable human occupational carcinogens (IARC group 2A); 113 possible human occupational carcinogens (IARC group 2B); and 18 occupations and industries that possibly, probably or definitely entail excess risk of cancer (IARC groups 1, 2A and 2B).
United States Department of Health and Human Services Report on Carcinogens (RoC) Substances on the RoC are classified into one of two groups: Known to be human carcinogen. Reasonably anticipated to be human carcinogenic. The 10th RoC classifies 52 substances into the known carcinogens group, and a further 176 substances into the reasonably anticipated carcinogens group.
United States Environmental Protection Ath Authority (EPA) Agents can be classified as: Carcinogenic to humans: when there is convincing epidemiologic evidence demonstrating causality between human exposure and cancer. Likely to be carcinogenic to humans: when the available data are adequate to demonstrate carcinogenic potential to humans. Suggestive evidence of carcinogenic potential: when the evidence from human or animal data is suggestive of carcinogenicity but is not sufficient for a stronger conclusion. Inadequate information to assess carcinogenic potential. Not likely to be carcinogenic to humans. the EPA are much more conservative than any other organization. They have only classified three substances (arsenic, benzene, chromium IV) as carcinogenic to humans, and a further 102 as likely or probable carcinogens. They have not evaluated any form of asbestos.
The most Important Occupational cancers
Lung cancer (Exposures) General workplaces Tobacco smoking is responsible for nearly 90% of all lung cancers. Second-hand smoke Byproducts of fossil fuel Air pollution Insufficient consumption of fruits and vegetables High doses of ionizing radiation Asbestos Radon chloromethyl ethers Polycyclic yy aromatic hydrocarbons Inorganic arsenic Chromium Nickel Mustard Gas
Lung cancer (findings) Symptoms & Signs Cough Hemoptysis Wheezing Dyspnea Weight loss Anorexia Fatigue Paraclinics CXR CT-scan Sputum cytology Fiberoptic Bronchoscopy Biopsy
Lung cancer (prevention) Avoidance of exposure Medical monitoring ( CXR, Sputum cytology )
Mesothelioma (exposure) Asbestosis (trivial contact) Crysotile, Amosite, Crocidolite, Tremolite, Anthophylite, Actinolite Crocidolite: the most potent carcinogen
Mesothelioma (findings) Symptoms & signs Chest pain Dyspnea Dry cough Weight loss Pleural effusion Friction rub paraclinics CXR CT-scan Thoracentesis Thotacotomy & thoracoscopy Sputum cytology SI-ADH LDH
Mesothelioma (prevention) OSHA PEL (1970) :5 Fiber/cm3 (1986):2 fiber/cm3 now: 0.1 fiber/cm3 Asbestos ban : since 1989 by EPA
Asbestos Ban (1989)
Bladder cancer (exposure) General The most important risk factor is cigarette smoking. Heavy coffee consumption (Possible risk factors ) Bladder infection with schistosoma Cyclophosphamide Long-term use of pain killers containing phenacetin, Urinary tract infections or low urine flow Genetic factors workplace Benzidine 2-naphthylamine Occupations in the dye, leather or rubber industry Chlornaphazine 4 chlorotoluidine l Phenacetine
Bladder cancer (findings) Symptoms & signs Hematuria (Painless, gross, intermittent) 80% Vesical irritability alone 20% In advance cases: Anemia Uremia Leg edema Paraclinics Urinary cytology (in up to 75% of patients is positive) Ultrasonography Excretory urography Cystoscopy & biopsy (definitive diagnosis)
Bladder cancer (prevention) Avoidance of exposure Medical monitoring : Urinary cytology (75% Sen. 99.9 Spes.) Immunocytology
Liver cancer (hepatic angiosarcoma) (exposure) Vinyl chloride Arsenic Copper, Lead, Zinc smelting Thorotrast (thorium dioxide) 1930-1955
Liver cancer (hepatic angiosarcoma) (findings) Symptoms & sings Paraclinics Asymptomatic (some time) Ultrasonography RUQ abdominal pain Weight loss Fatigue Hepatomegaly with ascitis Jaundice Splenomegaly Radionuclide liver scan Hepatic angiography Liver biopsy (hemorrhage) Lab data: Mild anemia (target cell & schistocyt), Leukocytosis, thrombocytopenia LFT LDH
Liver cancer (hepatic angiosarcoma) (prevention) Avoidance of exposure Medical monitoring (history, Ph/E, CBC, LFT, Ultrasonography)
تشكر از توجه شما با