Method of the cohort study--a practical example

The method is demonstrated in connection with a study of lung cancer among metal-workers exposed to oil mist. As exposure to oil mist is uncommon and lung cancer is common, the cohort study is the method of choice. Estimation of exposure, problems of selection, calculation of person-years etc is discussed. There was no increased morbidity from lung cancer.

Epidemiology of cancer of the nose and paranasal sinuses: current concepts

Cancer of the nose and paranasal sinuses (SNC) has been attributed to occupational exposure to nickel, chromium, radium, dichlordiethyl sulphide, isopropyl oil, and hydrocarbons. Occupational groups with an increased SNC risk include furniture, boot and show workers, and workers in U.S. countries heavily involved in both petroleum and chemical manufacturing; specific agents have not been identified with certainty. In most of the studies, the risk for developing SNC in the exposed workers was 21 to 100+ times greater than the risk for SNC in those who were not exposed. Undifferentiated and squamous histologies are associated with nickel refining; adenocarcinomas are found in woodworkers, boot and show manufacturers, and textile workers. Most occupations at risk for SNC were also at risk for cancer of other sites, particularly lung and skin cancer. Study of the epidemiology of SNC may identify unrecognized carcinogens and occupational groups at increased cancer risk.

Measurement of the responses of individuals to environmental stress and pollution: studies with bivalve molluscs

Certain physiological differences between individuals in different populations of the mussel, Mytilus edulis, are described. In particular, the scope for growth differs in space and time and may be used to assess the animals' physiological condition. When the required measurements are made in the field, the rates of growth predicted from the physiological data agree well with observed rates of growth. An alternative approach utilizes mussels transplanted to various waters, with indices of condition then measured in then measured in the laboratory under standard conditions; an example of this approach is illustrated. Laboratory experiments are used to equate various levels of physiological condition with fecundity, in an attempt to equate physiological effects on the individual with likely population damage. A cytochemical index of stress is described, based on the latency of lysosomal enzymes; spatial variability in this index, and its relation with the scope for growth, are discussed. Finally, the results of some experiments on the effects of petroleum hydrocarbons on mussels are described and the presence of inducible activity of NADPH-dependent tetrazolium reductase in the blood cells is demonstrated. Certain considerations that apply in adopting similar measurements of biological effects of pollution in environmental monitoring programmes are discussed.

Pulmonary function abnormalities in asymptomatic children after hydrocarbon pneumonitis

To assess the effect of hydrocarbon pneumonitis on the developing lung, we studied the pulmonary function of 17 asymptomatic children, 8 to 14 years after the initial insult. Fourteen of the 17 subjects (82%) had one or more pulmonary function abnormalities, the most frequent being a high volume of isoflow. Volume of isoflow, ratio residual volume to total lung capacity, slope of phase III, flow rates at 50% and 25% of vital capacity and 60% of the total lung capacity, one-second forced expiratory volume, and maximum midexpiratory flow rate differed significantly (P less than .05) from values in control groups. Closing volume and closing capacity were not significantly different. Residual abnormalities present in children after hydrocarbon pneumonitis can be explained on the basis of small airway obstruction and/or loss of elastic recoil. These children may be at risk for the development of chronic lung disease as adults when they are exposed to exogenous factors such as air pollution or smoking.

Identification and reduction of carcinogens in the respiratory environment

Epidemiological studies have implicated three factors in the overall increase of lung cancer--tobacco, especially cigarette smoking, urban pollution and, to a lesser extent, certain industrial respiratory environments. Some data were discussed on carcinogenic industrial inhalants, and on the possible effect of urban pollution. The reduction of pollution and that of specific environmental agents is stressed. Laboratory studies on the identification of carcinogens in cigarette smoke and their reduction toward the "less harmful cigarette" represent a part of this aspect.

Air pollution: its effects on health and respiratory disease--a review

A selective review of clinical and experimental data pertaining to air pollution and its effects on health and disease is presented. Various air pollutants, their effects on health and national air quality standard levels are outlined. The guidelines for asthmatic patients to follow during air pollution episodes are enumerated.

Toxic polyneuropathy of shoe-industry workers. A study of 122 cases

The toxic polyneuropathy observed in a group of shoe-industry workers in Italy was clinically characterised by a symmetrical prevalently distal motor deficit, with occasional marked weakness of pelvic girdle muscles, and frequently by only subjective sensory symptoms; non-specific disturbances usually preceded neurological signs. Subclinical cases of 'minimal' chronic neuropathy, characterised by alterations of a neurogenic type in the EMG without a reduction of motor nerve conduction velocity, were also observed. Worsening of the clinical picture, with further lowering of nerve conduction velocity, was noted in some cases up to four months after removal from the toxic environment. In the most severe cases clinical recovery took up to three years. The electromyographic and electroneurographic features were consistent with a mixed axonal neuropathy, with clear prevalence of the damage in the distal part of the nerve (dying-back neuropathy). Volatile substances, such as n-hexane and other low boiling point hydrocarbons found in high percentage in solvents and glues, are suggested as the causative agent.

Recent advances in investigations of toxicity of automotive exhaust

The influence of auto exhaust on man's health is difficult to gauge considering the intricacy of human environmental urban stresses and particularly of other air polluting (industrial, domestic) emissions. Epidemiological surveys made in road tunnel employees and in traffic officers have not demonstrated specific effects and have often been complicated by cigarette smoking as a factor. Long-term animal experiments run mostly on small rodents give evidence of little effect of the pathological actions of dilutions such as those encountered in high polluted cities. However the acute toxicity of gasoline exhaust emission is well known and mostly due to carbon monoxide. Considering the different types of cycles and operating conditions of vehicles (gasoline and diesel), auto exhaust gases constitute no more a chemical entity than they show, a definite toxicity. A great number of substances that they contain (nitrogen oxides, aldehydes, antiknock additives, heavy metals, possible catalysts are highly toxic as shown by in vivo and in vitro (mutagenic) tests. Interactions of the components are for the moment ignored or poorly understood. Besides, the evolution of the physicochemical properties and natures of the auto exhaust emission in the gaseous biotope of man under determined conditions of ultraviolet irradiation, temperature, and hygrometry provoke the formation of secondary products such as oxidants and ozone. Several experiments show clearly that irradiation increases the toxicity of auto exhaust significantly. For these reasons, geographical, meteorological, and chronological (circadian and seasonal) factors should be taken into consideration, especially with regard to emission standards.