(3) It is important to inquire _to what extent offensive trade effluvia are injurious to the public health_. It is impossible to bring statistics to bear on the inquiry, as other influences, apart from occupation, can scarcely be eliminated. The term “injurious to health” is capable of a double interpretation. It might mean either serious damage to health, or the mere production of bodily discomfort or other functional disturbance by the offensive effluvia, leading by its continuance to an appreciable impairment of vigour, though not to any actual disease. In the latter sense offensive effluvia have a deleterious effect on health. Such symptoms as loss of appetite, nausea, headache, occasionally diarrhœa, and general malaise are produced by effluvia of various kinds, but agreeing in being all offensive. “A condition of _dis_-ease or _mal_-aise is produced.” There is little difficulty in proving bad effects on the workmen, though the invariable defence of manufacturers is an appeal to the condition of health of their workmen. The workmen only remain such so long as they are healthy, and as they become disabled they necessarily cease to rank among workmen. The decomposition of putrefying organic matters is unquestionably dangerous. The general doctrine of sanitation that filth is one of the chief factors in producing disease is certainly applicable to trade effluvia as well as to general sanitation. It has been alleged on behalf of such effluvia as chlorine sulphurous acid and tar vapours that they are useful disinfectants; but modern research has shown that disinfectants, in order to be of practical use, must be in such a concentrated condition that the air containing them is irrespirable. Probably such septic diseases as erysipelas are favoured by organic trade effluvia. (4) _The means available_ to prevent or minimise the nuisances arising from trade effluvia vary with the character of the processes. The general principles on which treatment must be founded depend, as Dr. Ballard points out, on a recognition of the following kinds of effluvia:— Effluvia dependent— 1. On the accumulation of filth on or about business premises, or on its removal in an offensive condition. 2. On a generally filthy condition of the interior of buildings and premises and utensils generally. 3. On an improper mode of disposal of offensive refuse, liquid or otherwise. 4. On insufficient or careless arrangements in reception of offensive materials of the trade, or in removal of offensive products. 5. On an improper mode of storing offensive materials or products. 6. On the escape of offensive gases or vapours given off during some part of the trade processes.