Session 18 Environmental pathology

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Lecture Notes

Session 18: Environmental Pathology

Alex Simon (MD)

Learning tasks

At the end of this session, students are expected to be able to:

Define environmental diseases.

Explain air pollution.

Explain industrial and agricultural exposures.

Explain effects of tobacco product use.

Definition

Environmental diseases can originate from occupational exposures, polluted ambient air, chemicals taken to the body through the lung or GIT for several reasons, or from noxious physical agents that come in contact to the body.

It refers to disorders caused by exposure to chemical or physical agents in the ambient, workplace, and personal environments.

AIR POLLUTION

Air is most of the time, loaded with potential causes of diseases.

Agents from the air like microorganisms contaminating food and water, chemical and particulate pollutants found in the air are common causes of diseases.

There are two (2) types of air pollution.

Outdoor air pollution.

Indoor air pollution.

Outdoor air pollution

The ambient air in industrialized nations is contaminated with gaseous and particulate pollutants.

Pollutants may cause trivial irritation to the upper respiratory pathways, acute or chronic injury to the lungs, and some in causation of lung cancer.

The six (6) common outdoor air pollutants are

Ozone.

Sulfur dioxide.

Carbon monoxide.

Nitrogen dioxide.

Lead.

Particulate matter.

Ozone

Ozone is one of the most pervasive air pollutants

It is a gas formed by sunlight-driven reactions involving nitrogen oxides, which are released mostly by automobile exhaust.

Together with oxides and fine particulate matter, ozone forms the familiar smog (from smoke and fog)

Its toxicity stems from its participation in chemical reactions that generate free radicals, which injure the lining cells of the respiratory tract and the alveoli.

Sulfur dioxide, particles and acid aerosols

Sulfur dioxide, particles, and acid aerosols are emitted by coal- and oil-fired power plants and industrial processes burning these fuels.

Particles appear to be the main cause of morbidity and death.

Particles less than 10 µm in diameter are particularly harmful, since when inhaled they are carried by the airstream all the way to the alveoli.

Phagocytosed by macrophages and neutrophils, causing the release of mediators and inciting an inflammatory reaction.

But larger particles are removed in the nose or are trapped by the mucociliary and as a result are less dangerous.

Carbon monoxide (CO)

Carbon monoxide (CO) is a nonirritating, colorless, tasteless, odorless gas.

It is produced by the incomplete oxidation of carbonaceous materials.

Its sources include automotive engines, industries using fossil fuels, home oil burners, and cigarette smoke.

The low levels often found in ambient air may contribute to impaired respiratory function but usually are not life-threatening.

Carbon monoxide (CO) cont…

However, persons working in confined environments with high exposure to fumes, such as tunnel and underground garage workers, may develop chronic poisoning.

CO is included here as an air pollutant, but it also is an important cause of accidental and suicidal death.

Carbon monoxide (CO) cont…

CO is a systemic asphyxiant that kills by binding to hemoglobin and preventing oxygen transport.

Hemoglobin has a 200-fold greater affinity for CO than for O2.

The resultant compound, carboxyhemoglobin, is incapable of carrying oxygen.

Hypoxia leads to central nervous system (CNS) depression.

Indoor air pollution

The commonest pollutant are

Tobacco smoke.

Carbon monoxide

Nitrogen dioxide.

Asbestos.

Wood smoke.

Formaldehyde.

Bioaerosols.

Radon.

Other indoor air pollutants

Wood smoke.

Containing various oxides of nitrogen and carbon particulates.

Predisposes exposed persons to lung infections and may contain carcinogenic polycyclic hydrocarbons.

Radon.

A radioactive gas derived from uranium, is widely present in soil and in homes.

Low-level chronic exposures in the home does not increase lung cancer risk, at least for nonsmokers compared to uranium miners.

Other indoor air pollutants cont…

Bioaerosols.

May contain pathogenic microbiologic agents, such as those that can cause Legionnaires’ disease, viral pneumonia, and the common cold, as well as allergens derived from pet dander, dust mites, and fungi and molds, which can cause rhinitis, eye irritation, and even asthma.

Air pollution cont…

The adverse effects of air pollutants on lung depend upon a few variables that include:

Longer duration of exposure

Total dose of exposure

Impaired ability of the host to clear inhaled particles

Particle size of 1-5 μm capable of getting impacted in the distal airways to produce tissue injury.

Industrial and agricultural exposures

Organic solvents

Polycyclic hydrocarbons

Organochlorines

Dioxins and PCBs

Bisphenol A (BPA)

Exposure to vinyl chloride

Inhalation of mineral dusts

Organic solvents

Some, such as chloroform and carbon tetrachloride, are found in degreasing and dry cleaning agents and paint removers.

Acute exposure to high levels of vapors from these agents can cause dizziness and confusion, leading to CNS depression and even coma.

Lower levels have toxicity for the liver and kidneys.

Occupational exposure of rubber workers to benzene and 1,3-butadiene increases the risk of leukemia.

Polycyclic hydrocarbons

Released during the combustion of coal and gas, particularly at the high temperatures used in steel foundries, and also are present in tar and soot.

Polycyclic hydrocarbons are among the most potent carcinogens, and industrial exposures have been implicated in the causation of lung and bladder cancer.

Pott identified soot as the cause of scrotal cancers in chimney sweeps in 1775.

Organochlorines (and halogenated organic compounds)

Important organochlorines used as pesticides are DDT (dichlorodiphenyltrichloroethane).

Acute DDT poisoning in humans causes neurologic toxicity.

Most organochlorines are endocrine disruptors.

Nonpesticide organochlorines include polychlorinated biphenyls (PCBs) and dioxin.

Dioxins and PCBs can cause

Skin disorders such as folliculitis and acneiform dermatosis.

It can be accompanied by abnormalities in the liver and CNS.

Other industrial exposures

Bisphenol A (BPA).

Used in the synthesis of polycarbonate food and water containers and food bottles and cans.

BPA has long been known as a potential endocrine disruptor.

Exposure to vinyl chloride.

Used in the synthesis of polyvinyl resins, was found to cause angiosarcoma of the liver, a rare type of liver tumor.

Inhalation of mineral dusts

Causes chronic, non-neoplastic lung diseases called pneumoconioses.

This group of disorders includes diseases induced by organic and inorganic particulates as well as chemical fume- and vapor-induced non-neoplastic lung diseases.

Inhalation of mineral dusts cont…

The most common pneumoconioses are caused by exposures to mineral dust

Coal dust (in mining of hard coal) causing coal workers pneumoconiosis

Silica (in sandblasting and stone cutting) causing silicosis.

Asbestos (in mining, fabrication, and insulation work) causing asbestosis.

Beryllium (in mining and fabrication) causing berylliosis.

Tobacco smoking

Tobacco smoke contains more than 2000 compounds.

Among these are

Nicotine, which is responsible for tobacco addiction

Strong carcinogens mainly, tar, polycyclic aromatic hydrocarbons, nitrosamines, and aromatic amines.

Tobacco smoking cont…

Nicotine, an alkaloid present in tobacco leaves, is not a direct cause of tobacco-related diseases, but it is highly addictive.

Nicotine binds to receptors in the brain and, through the release of catecholamines, is responsible for the acute effects of smoking, such as increased heart rate and blood pressure, and increased cardiac contractility and output.

Tobacco smoking cont…

Tobacco is the most common exogenous cause of human cancers, being responsible for 90% of lung cancers.

The main culprit of lung cancers is cigarette smoking

But smokeless tobacco in its various forms (snuff, chewing tobacco) also is harmful to health and is an important cause of oral cancer.

Not only does the use of tobacco products create personal risk, but passive tobacco inhalation from the environment (“secondhand smoke”) can cause lung cancer in nonsmokers.

Effects of tobacco

The most common diseases caused by cigarette smoking involve the lung and include:

Emphysema.

Chronic bronchitis.

Lung cancer.

Chronic bronchitis and emphysema (one of the Chronic obstructive pulmonary diseases) are the most common.

Effects of tobacco smoking to respiratory system

Agents in smoke have a direct irritant effect on the tracheobronchial mucosa, producing inflammation and increased mucus production (bronchitis).

Cigarette smoke also causes the recruitment of leukocytes to the lung, increasing local elastase production and subsequent injury to lung tissue that leads to emphysema.

Components of cigarette smoke, particularly polycyclic hydrocarbons and nitrosamines , are potent carcinogens in animals and probably are involved in the causation of lung carcinomas in humans .

Effects of tobacco smoking to cardiovascular system

Atherosclerosis and its major complication, myocardial infarction, are strongly linked to cigarette smoking.

The causal mechanisms probably relate to several factors, including increased platelet aggregation, decreased myocardial oxygen supply (because of lung disease coupled with hypoxia related to CO in cigarette smoke) accompanied by increased oxygen demand, and a decreased threshold for ventricular fibrillation.

Types of cancers related to tobacco smoking

Tobacco smoke contributes to the development of cancers of the oral cavity, esophagus, pancreas, and bladder.

The combination of tobacco (chewed or smoked) and alcohol consumption has multiplicative effects on the risks of oral, laryngeal, and esophageal cancers. Also risk of peptic ulcers.

Effects of tobacco smoking to pregnancy

Maternal smoking increases the risk of

Spontaneous abortions.

Preterm births.

Results in intrauterine growth retardation.

Passive smoke inhalation

Exposure to environmental tobacco smoke (passive smoke inhalation) is also associated with detrimental effects.

It is associated with the risk of lung cancer.

Children living in a household with an adult who smokes have an increased frequency of respiratory illnesses and asthma.

Passive smoke inhalation in nonsmokers can be estimated by measuring the blood levels of cotinine, a metabolite of nicotine.

Key points

The most common air pollutants are ozone.

Carbon monoxide binds to hemoglobin and preventing oxygen transport.

Polycyclic hydrocarbons have been implicated in the causation of lung and bladder cancer.

Acute DDT poisoning in humans causes neurologic toxicity.

Inhalation of mineral dust causes chronic, non-neoplastic lung diseases called pneumoconioses.

Cigarette smoking causes deaths mostly from cardiovascular disease, various types of cancers, and chronic respiratory problems.

Review questions

Define environmental diseases.

Mention six (6) common outdoor air pollutants.

List six (6) common indoor air pollutants.

Outline four (4) diseases falls under pneumoconiosis.

Explain five (5) efffects of tobacco smoking in human health.

References

Bezabeh M.; Tesfaye A.; Ergicho B. et al (2004): General pathology lecture notes for Health Sciences students. Ethiopia Public Health Training Initiative. Pg. 231-239.

Goljan E.;(2007): Rapid Review Pathology (2th Ed.) Elsevier Saunders, USA. Pg. 109, 114-115.

Kumar V. ; Abbas A. K. ; Aster J. C.;(2013): Robbins and Contran Pathologic Basis of Disease (9th Ed.) Elsevier Saunders, USA. Pg. 272-280.

Mohan H.;(2010): Text book of Pathology (6th Ed.) Jaypee Brothers Medical Publishers, India. Pg. 236-242.

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Session 18 Environmental pathology

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Lecture Notes