Pollutants such as those found in tobacco smoke, asbestos, and fungal spores can adversely impact on the respiratory system by causing short-term and long-term damage.
Asbestos was a building material whose disturbed, fine particles lodged themselves in the lungs upon inhalation, and caused damage over time. Symptoms only occurred many years or decades after exposure.
Fungal spores are omnipresent in the air and are usually dealt with by the immune system without trouble. If inhaled in high quantity they can sensitise the respiratory system and be dangerous to sufferers of asthma, or cause more severe infections in those who are immunocompromised.
The chemicals contained in tobacco cigarette smoke (several thousand types) do damage to the cilia that line the respiratory tract and move dirt particles away from the lungs e.g. pollutants, pathogens, dust. These protrusions from the lungs, trachea and nose are sensitive to toxins and following long periods of sustained damage can cease to function. Cilia damage results in a failure to remove lung mucus and thicker mucus building up in the lungs. This causes an unproductive cough.
Short-term, smoking decreases circulatory and lung function, which returns back to previous levels shortly after stopping smoking. Many other effects are long-term.
The buildup of debris in the respiratory tract renders someone more prone to bacterial infection such as chronic bronchitis. This manifests itself through inflammation of the airways and constitutes a kind of chronic obstructive pulmonary disease (COPD). Symptoms include coughing, increased mucus production, shortness of breath and wheezing. Chronic, as opposed to acute bronchitis lasts for more than 3 months.
Fibrosis is the accumulation of scar tissue as a result of damage or bacterial infection. It affects the aveoli primarily, as they are ever so small and fragile. So fibrosis is not a disease in its own right, but a result of others.
Scar tissue is fibrous connective tissue and prevents good lung function, therefore symptoms caused are coughing and shortness of breath. Damaged alveoli will not contribute to the diffusion of oxygen into red blood cells.
Emphysema is a nasty disease. It is caused by excessive smoking (or air pollutants) over a lifetime and results in a steep decline in lung function, to the point where very severe cases require an oxygen tank connected to the airways at all times.
Fibrosis occurs in the lungs as part of emphysema, which results in thicker alveolar walls which increase the diffusion pathway of oxygen and carbon dioxide, therefore decreasing the rate of diffusion. Another side effect is a loss of elasticity which makes breathing out more difficult.
Lung cancer is caused in the most part by prolonged smoking of tobacco or other products as well as prior exposure to asbestos, and is a cancer that starts in the lungs. Symptoms include coughing, potentially coughing blood, persistent chest infections, chest pain, breathlessness and lack of energy. There are two main types of lung cancer, and depending on whether it has spread to the rest of the body and how soon it is identified, treatment includes surgery to remove the tumour, chemotherapy, radiotherapy and other emerging biological treatments.
Asthma does not incur any damage to the lungs like the above diseases do. Fibrosis does not take place, and the surface area of the alveoli is unaffected. What does take place is that the terminal bronchioles’ smooth muscles constrict, resulting in less air reaching the lungs. Symptoms include short-term shortness of breath and an increased secretion of mucus.
Things which bring on asthma (which is an exaggerated, unnecessary immune response) include stress, cold, exercise and air pollution. Prolonged exposure to air high in fungal spores can sensitise the respiratory system. Asthma is treated with antihistamines and steroids, which reduce the response, as well as beta agonists (bronchodilators) which relax the smooth muscles.
Sourcing treatments from plants
Plants are a key source of prospective medicines to treat respiratory diseases. Theophylline is used to treat COPD and asthma. It is richly found in tea and cocoa (Theobroma cacao) plants, and works by reducing inflammation and the immune response.
Topotecan is a partially synthetic drug based on a natural chemical found in the bark of a tree (Camptotheca acuminata) native to China, used to treat some cancers including lung cancer. Its activated form (lactone) works by binding to DNA and its cleavage enzyme, and blocking the DNA replication machinery. This results in DNA damage through a double strand break that doesn’t get fixed, resulting in cell death.
Other drugs originating in plants include aspirin (from willow trees, Salix spp.) and quinine (from the flowering plants Clinchona spp.). Aspirin is an anti-inflammatory, anti-coagulant drug used for a broad spectrum of conditions, while quinine is used specifically against malaria.
Testing treatments and providing guidelines
Experiments must adhere to guidelines such as risk assessment, reproducibility and validity of results, time and cost effectiveness, etc. For example, in a clinical trial where clinicians administer drugs and placebos randomly to patients, a double-blind experimental design is required where neither the clinicians nor the patients are aware of whether they are assigned the drug or the placebo.
Clinical trials are designed to assess the value of treatment that is newly discovered, before approving and implementing it for large-scale use on patients. They start with a small sample of patients to test just the safety of the drug, and gradually progress to larger patient populations to look for the efficacy of the drug, whether it works as intended, potential side effects, and whether the benefit is greater than existing treatments.
Therefore, clinical trials are split into phases.
This model enables the minimising of negative effects. Clinical trials have taken place in the past that resulted in the illness and even death of participants, so a small starting sample is crucial. Throughout Phases II and III, the efficacy of the new treatment is compared to a placebo, and even other existing treatments.
Phase IV is a larger, overarching process of continued monitoring of effects as the treatment is being deployed internationally and in tandem with other treatments.
Following licensing, the cost and limitations of the treatment are assessed by the National Institute for Health and Care Excellence (NICE) to produce guidelines for the use of the treatment by the NHS in the UK and by other healthcare practitioners and institutions.
NICE also produce guidelines for all those involved in the processes that affect public health, as well as expenditure guidelines for new health technologies. For example, there are guidelines for those making decisions regarding new roads and infrastructure regarding walking and cycling, in an attempt to reduce the ill effects of air pollution. In terms of emerging high technology to be used by the NHS, there are consultations regarding what threshold of spending should be granted by default e.g. £100,000 or less.
The consultation paper (viewable here) reveals that the pressures of limited budgets are met with potentially unrealistic spending. For example, some thought that £100,000 was far too low for most technologies, and especially did not benefit those with rare diseases.