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Blowflies and slaughterhouses
P U B L I C H E A L T H , April, 195I
116 widespread disintegration of children's teeth caused indirectly by the absence of this trace element, could they be right ?
Respiratory Sickness and Atmospheric Pollution For long enough now it has been contended that atmospheric pollution is harmful to human life and for as long there has been lacking proof of the extent to which the contention is justified. When a disaster of the magnitude of that of the Meuse Valley or of Donora occurs, it is fairly easy to associate cause and effect. Unfortunately, however, there have not been available in either ease precise data concerning the actual pollutants or their degree of concentration at the time of the disasters and so, though the clinical picture produced in man is known, the factor or combination of factors that went into its production can only be conjectured. With the lesser degrees of pollution usually met with in this country, not only are the more obvious clinical effects to be looked for amongst those less well -equipped to resist, but they have to be recognised often against a background of pre-existing or newly supervened disease. T h e problem is the determination of the extent to which known atmospheric pollution contributes to the production of respiratory sickness or the aggravation of previously existing cardio respiratory disease and so far there is a dearth of information on the subject. T h e information that is available suggests that it is the later age groups, together with sufferers from cardio respiratory disease, that are most likely to show reaction to atmospheric irritants and evidence of reaction in young children is lacking. A recent report prepared, o n the instruction of the Northamptonshire County Council, by its Medical Officer of Health,* demonstrates an excessively high infant mortality rate, especially beyond the neo-natal range, in the urban district of Corby to be due to a relatively higher deathrate from respiratory disease amongst infants. When searching for further differences between Corby and the other urban districts in Northamptonshire, Dr. Smith draws attention to the high degree of atmospheric pollution prevailing in Corby, but wisely does no more than suggest a possible association between the two. T h e special enquiry into the effects of atmospheric pollution on the incidence of respiratory diseases in Corby published in the December issue of this journal,t concluded that there was a considerably higher incidence of bronchitis and pneumonia, but less asthma, than in a Scottish rural practice and that an unduly large number of respiratory illnesses was seen two to three days after a heavy fog ; but the relative importance of fog and pollution in the causation of these illnesses could not be assessed on the available data. These two reports are important inasmuch as they draw attention to the excessive respiratory morbidity and mortality occurring in an area of high atmospheric pollution and admit a failure to prove a relationship between the two. Is further emphasis needed to show the lack of scientific knowledge on the connection between respiratory illness and atmospheric pollution ? It seems as though information is needed of other circumscribed areas in the country showing the same phenomena and of those, if any, showing heavy pollution without a demonstrable increase of respiratory sickness. It would be necessary to know the composition of the pollution in the areas concerned and it would be necessary to evolve a method of determining both for individual and grouped atmospheric irritants a threshold valve above which a reaction of respiratory irritation occurs in selected community groups. T h e r e is here a long delayed piece of research that could well be carried out co-operatively by the Society, the Department of Scientific and Industrial Research and other interested scientific bodies. * Infant Mortality in Corby. By C. MiUiken Smith, M.D., D.P.B. ~"A Survey of Respiratory Illness in a New Industrial Town. By lan Sutherland, M.A., D.PHIL., and Dagmar C. Wilson, M.D., M.R.C.P., F.R.C.O.G., PUBLICHEALTH (1950.) 64. 17-21
Blowflies and Slaughterhouses Successful experiments to prevent blowflies breeding in slaughterhouses have recently been carried out by the Pest Infestation Laboratory of the Department of Scientific and Industrial Research. T h e experiments took place at one of the largest slaughterhouses in Southern England. T h e problem of blowfly infestation is one which has caused concern for some time. T h e refuse in slaughterhouses is an ideal food for blowfly larvae and, in one experiment, over 75,000 maggots emerged from 45 lb. of refuse which was exposed to blowfly attack for only eight hours. A ton of refuse is therefore a potential breeding ground for nearly four million blowflies and many slaughterhouses produce more than a ton a day. T h e blowflies are not only bred on the premises but are also attracted from other breeding grounds such as refuse disposal depots, and the yards of butchers' shops and restaurants. Most of the blowflies were found just outside the slaughtering rooms. T h e y do not normally settle on the inside of a building unless it is brightly lit by direct sunlight. T h e y enter the room by following a shaft of sunlight through an open doorway or window and after settling on the meat leave in the same way. Five per cent. D D T dust was applied regularly to the refuse heaps and nearby vegetation where most of the flies could be expected to come into contact with it. During the past two years this treatment, combined with systematic rotational storage and collection of refuse, has prevented all breeding of blowflies on the slaughterhouse premises. Various other treatments were used and over 80,000 blowflies from the treated refuse heaps were examined to discover what the effects were. All the treatments had some repellent action against adult blowflies, but D D T dust was far the most successful. T h r e e treatments, D D T dust, D D T emulsion and BH5 dust killed an appreciable number of adult blowflies as they emerged from the pupae. Flies will settle to rest on outside walls if they are sunlit, particularly towards the end of the day when the wall is warm and the flies are gorged with food. All the walls near the slaughtering rooms were sprayed with a D D T wettable powder to kill these. As a result the proportion of one species of fly infesting the slaughterhouse dropped from 10% to less than 1%. Laboratory studies on heaps of infested refuse have confirmed field observations that most mature blowfly grubs migrate at night in search of suitable places in which to pupate. Even when the food the larvae were living in was kept in constant darkness during the whole period of development and migration, more than 90% of the larvae still migrated between 6 p.m. and 9 a.m.
The Industrial Court The hearing by the Industrial Court of the management ana staff sides' cases regarding the salaries of Deputy Medical Officers of Health, Area or Divisional Medical Officers and'Medical Officers holding "mixed " appointments was concluded at the third sitting held on April 16th. The Court asked for further information to be collected on certain points but it is anticipated that its Award will be made before the end of May.
Dual Appointments It is understood that both sides of Whitley Committees B and C have now appointed their representatives for joint discussions on the conditioias of appointment and service of medical officers who hold dual appointments, i.e., serve both local authorities and Regional Hospital Boards. The Staff side is pressing for an early meeting of the Joint Committee.
Ordinary Meeting of the Society An Ordinary Meeting of the Society will be held at B.M.A. House, Tavistock Square, London, W.C.1, at 12.30 p.m. or as soon as possible thereafter at the conclusion of the preceding Council Meeting, on Friday, May 18th. The business will include the election of the President for Session 1951-52 and the presentation by the Metropolitan Branch of a portrait of Sir Allen Daley (President, 1947-48).
116 widespread disintegration of children's teeth caused indirectly by the absence of this trace element, could they be right ?
Respiratory Sickness and Atmospheric Pollution For long enough now it has been contended that atmospheric pollution is harmful to human life and for as long there has been lacking proof of the extent to which the contention is justified. When a disaster of the magnitude of that of the Meuse Valley or of Donora occurs, it is fairly easy to associate cause and effect. Unfortunately, however, there have not been available in either ease precise data concerning the actual pollutants or their degree of concentration at the time of the disasters and so, though the clinical picture produced in man is known, the factor or combination of factors that went into its production can only be conjectured. With the lesser degrees of pollution usually met with in this country, not only are the more obvious clinical effects to be looked for amongst those less well -equipped to resist, but they have to be recognised often against a background of pre-existing or newly supervened disease. T h e problem is the determination of the extent to which known atmospheric pollution contributes to the production of respiratory sickness or the aggravation of previously existing cardio respiratory disease and so far there is a dearth of information on the subject. T h e information that is available suggests that it is the later age groups, together with sufferers from cardio respiratory disease, that are most likely to show reaction to atmospheric irritants and evidence of reaction in young children is lacking. A recent report prepared, o n the instruction of the Northamptonshire County Council, by its Medical Officer of Health,* demonstrates an excessively high infant mortality rate, especially beyond the neo-natal range, in the urban district of Corby to be due to a relatively higher deathrate from respiratory disease amongst infants. When searching for further differences between Corby and the other urban districts in Northamptonshire, Dr. Smith draws attention to the high degree of atmospheric pollution prevailing in Corby, but wisely does no more than suggest a possible association between the two. T h e special enquiry into the effects of atmospheric pollution on the incidence of respiratory diseases in Corby published in the December issue of this journal,t concluded that there was a considerably higher incidence of bronchitis and pneumonia, but less asthma, than in a Scottish rural practice and that an unduly large number of respiratory illnesses was seen two to three days after a heavy fog ; but the relative importance of fog and pollution in the causation of these illnesses could not be assessed on the available data. These two reports are important inasmuch as they draw attention to the excessive respiratory morbidity and mortality occurring in an area of high atmospheric pollution and admit a failure to prove a relationship between the two. Is further emphasis needed to show the lack of scientific knowledge on the connection between respiratory illness and atmospheric pollution ? It seems as though information is needed of other circumscribed areas in the country showing the same phenomena and of those, if any, showing heavy pollution without a demonstrable increase of respiratory sickness. It would be necessary to know the composition of the pollution in the areas concerned and it would be necessary to evolve a method of determining both for individual and grouped atmospheric irritants a threshold valve above which a reaction of respiratory irritation occurs in selected community groups. T h e r e is here a long delayed piece of research that could well be carried out co-operatively by the Society, the Department of Scientific and Industrial Research and other interested scientific bodies. * Infant Mortality in Corby. By C. MiUiken Smith, M.D., D.P.B. ~"A Survey of Respiratory Illness in a New Industrial Town. By lan Sutherland, M.A., D.PHIL., and Dagmar C. Wilson, M.D., M.R.C.P., F.R.C.O.G., PUBLICHEALTH (1950.) 64. 17-21
Blowflies and Slaughterhouses Successful experiments to prevent blowflies breeding in slaughterhouses have recently been carried out by the Pest Infestation Laboratory of the Department of Scientific and Industrial Research. T h e experiments took place at one of the largest slaughterhouses in Southern England. T h e problem of blowfly infestation is one which has caused concern for some time. T h e refuse in slaughterhouses is an ideal food for blowfly larvae and, in one experiment, over 75,000 maggots emerged from 45 lb. of refuse which was exposed to blowfly attack for only eight hours. A ton of refuse is therefore a potential breeding ground for nearly four million blowflies and many slaughterhouses produce more than a ton a day. T h e blowflies are not only bred on the premises but are also attracted from other breeding grounds such as refuse disposal depots, and the yards of butchers' shops and restaurants. Most of the blowflies were found just outside the slaughtering rooms. T h e y do not normally settle on the inside of a building unless it is brightly lit by direct sunlight. T h e y enter the room by following a shaft of sunlight through an open doorway or window and after settling on the meat leave in the same way. Five per cent. D D T dust was applied regularly to the refuse heaps and nearby vegetation where most of the flies could be expected to come into contact with it. During the past two years this treatment, combined with systematic rotational storage and collection of refuse, has prevented all breeding of blowflies on the slaughterhouse premises. Various other treatments were used and over 80,000 blowflies from the treated refuse heaps were examined to discover what the effects were. All the treatments had some repellent action against adult blowflies, but D D T dust was far the most successful. T h r e e treatments, D D T dust, D D T emulsion and BH5 dust killed an appreciable number of adult blowflies as they emerged from the pupae. Flies will settle to rest on outside walls if they are sunlit, particularly towards the end of the day when the wall is warm and the flies are gorged with food. All the walls near the slaughtering rooms were sprayed with a D D T wettable powder to kill these. As a result the proportion of one species of fly infesting the slaughterhouse dropped from 10% to less than 1%. Laboratory studies on heaps of infested refuse have confirmed field observations that most mature blowfly grubs migrate at night in search of suitable places in which to pupate. Even when the food the larvae were living in was kept in constant darkness during the whole period of development and migration, more than 90% of the larvae still migrated between 6 p.m. and 9 a.m.
The Industrial Court The hearing by the Industrial Court of the management ana staff sides' cases regarding the salaries of Deputy Medical Officers of Health, Area or Divisional Medical Officers and'Medical Officers holding "mixed " appointments was concluded at the third sitting held on April 16th. The Court asked for further information to be collected on certain points but it is anticipated that its Award will be made before the end of May.
Dual Appointments It is understood that both sides of Whitley Committees B and C have now appointed their representatives for joint discussions on the conditioias of appointment and service of medical officers who hold dual appointments, i.e., serve both local authorities and Regional Hospital Boards. The Staff side is pressing for an early meeting of the Joint Committee.
Ordinary Meeting of the Society An Ordinary Meeting of the Society will be held at B.M.A. House, Tavistock Square, London, W.C.1, at 12.30 p.m. or as soon as possible thereafter at the conclusion of the preceding Council Meeting, on Friday, May 18th. The business will include the election of the President for Session 1951-52 and the presentation by the Metropolitan Branch of a portrait of Sir Allen Daley (President, 1947-48).