Inflammatory processes resulting from infections of bronchi and lungs, scarring and tissue destruction, as well as impaired pulmonary circulation, are frequent lung disorders. Infants and the elderly are especially vulnerable to acute respiratory infections, which can be fatal. Since the lungs literally filter the venous blood drainage from the entire body, they often become involved secondarily by blood-borne processes; many malignant tumours eventually metastasis to the lungs. More important still is the steadily rising incidence of primary malignancy of the lung and its relationship to cigarette smoking and environmental pollution.
The average adult breathes once every four seconds, 960 times an hour, almost 8.5 million times a year. With each breath, is inhaled into the lungs hundreds of airborne substances, some naturally occurring, some the by-product of human activity. For those who live in cities, many of those substances are pollutants that may increase risk of respiratory problems and cancer. Six of the most prevalent and health-threatening air pollutants are carbon monoxide, sulphur dioxide, nitrogen oxides, lead, particulate matter and ozone. Ground-level ozone, aggravates asthma, and it can also reduce lung capacity and decrease the body's ability to fight off infection. Soot, or particulate matter, can cause bronchitis, chronic lung disease and irritation of the eyes and throat. Many hazardous air pollutants, such as vinyl chloride, arsenic and benzene, are carcinogens.
Worldwide mortality rates for acute respiratory infections are highest in infants and, in some countries, exceeded 2,000 for every 100,000 liveborn babies. The rate declines in childhood and early adult life, but increases progressively with age in the middle and old age groups. Acute respiratory infections in infants and children below 15 years of age account for 20.3% of the total number of deaths from all causes, against the 4.2% represented by deaths from the same cause in persons belonging to the age group 55 years and over. Some acute respiratory infections leave patients with sequelae and are known also to exacerbate already existing diseases of the respiratory tract; both situations may lead to the development of chronic lung conditions.
Chronic respiratory diseases (including chronic bronchitis, emphysema, and bronchial asthma) represent an average of 2.9% of all deaths reported for 1972, the highest mean percentage being reported from Africa (6.3%) and the lowest from Asia (2.0%). Of all deaths from chronic respiratory diseases, 18.4% occurred in infants and children and 81.6% in adults (15 years and over).
Chronic respiratory diseases are responsible also for widespread morbidity and invalidity in several parts of the world, in spite of the fact that some causative or aggravating factors (such as smoking, air pollution, socioeconomic conditions and respiratory infections in children) are already known and could be ameliorated or removed. With due reservations concerning differences in criteria, data from the World Health Organization over recent years indicate cases of this problem in the following countries: Africa – Mauritius;America – Brazil, Canada, El Salvador; Asia – Hong Kong, Israel, Japan, Kuwait, Singapore, Sri Lanka, Syria, Thailand; Pacific – Australia, New Zealand, Papua New Guinea; Europe – Austria, Bulgaria, Czechoslovakia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, UK, Yugoslavia.
In the WHO Europe region, diseases of the respiratory system cause 6% of all deaths; that proportion was roughly the same in 1995 as in 1990. Tobacco smoking is contributing to the high and rising mortality rates in the NIS countries. Asthma, allergy and other forms of respiratory sensitivity have increased in prevalence in many countries in western Europe. These diseases are potentially linked with environmental conditions. The high prevalence among children is of special concern.