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Teachers deaths
The Statistical Analysis

Part of "Information on asbestos in schools"


HSE statistics
Tables within the HSE mesothelioma statistics are based on the person’s occupation recorded on their death certificate. Relevant extracts from those statistics are included at Annex 1. During the investigation there has been considerable discussion with the HSE about these statistics and pertinent details of the discussions are included as part of this paper
Mesothelioma deaths
Mesothelioma is almost always caused by exposure to asbestos 119 and is always fatal. The statistics list the numbers of deaths from mesothelioma in each occupation. The number of mesothelioma deaths therefore gives an indication of the level of asbestos exposure experienced by people employed in each occupation.
Terms used in Statistics

Expected Deaths The term “Expected Deaths” is used in the HSE tables. It is a misleading term for all it shows is the numbers of mesothelioma deaths that can be “Expected “ in each profession based purely on a mathematical calculation of proportions 120. What it does not show is the number of deaths one would expect in each profession based on the assumed risk from asbestos exposure. Consequently the figure given for “Expected deaths” among teachers is comparatively high purely because there are a lot of teachers, and not because one should expect teachers to be exposed to a lot of asbestos.

Proportional Mortality Ratio The Proportional Mortality Ratio (PMR) is shown for each profession. The number of people in each occupation is different, therefore a large number of deaths from mesothelioma in an occupation employing very few people would be more remarkable than the same number of deaths in an occupation employing many thousands of people. A system has been devised to reflect this, and that is called the Proportional Mortality Ratio. It gives a comparison of mesothelioma deaths between occupations. A PMR of 100 shows that the number of mesothelioma deaths in a particular occupation is average for all the occupations. However that includes the high risk professions such as ship-building and the construction industry where asbestos exposure is known to occur. In those occupations the number of actual deaths is understandably far higher than the number of “Expected Deaths” and consequently the PMRs are far higher than 100.

Female teacher deaths three times higher than expected
Female with no asbestos exposure would have PMR of 36 One would presume that a teacher should suffer little or no asbestos exposure 121, and hence the number of deaths that one would expect should be in line with people who have had no exposure or only background levels of exposure. The HSE mesothelioma statistics have a section entitled “Interpretative issues” 122 which describes a hypothetical scenario where a female with no asbestos exposure would have a PMR of about 36. (this figure is derived from the number of cases where exposure is deemed as “background”) 123 This figure is important when considering the PMRs of any of the occupations.
  Female teachers’ deaths are three times higher than one would expect in a profession with little or no asbestos exposure. The PMR of 100 given for female school teachers shows that the number of deaths is average for all occupations and hence the level of exposure is the average for all occupations. (using the Southampton coding)124 ( Stats 5) What it certainly does not show is that the level of exposure is nil or at background levels, for that PMR would be 36. What it does show is that there has been a considerable level of asbestos exposure among female school teachers. The number of deaths is almost three times higher than one should expect in an occupation where the asbestos fibre levels should be no more than that of normal background levels.
Male teachers' deaths far higher than they should be

Male teachers’ deaths far exceed the number that one should expect in a profession with little or no asbestos exposure.The same interpretative issues gives a PMR of 6 for men with a hypothetical zero exposure. (This figure is less than that of females purely because the total number of male mesothelioma deaths is far greater than that of females, and the number of background cases represents a smaller proportion of the whole.)125 Male teachers were usually the ones who taught science and workshop skills, and their greater number of deaths resulting from those exposures is perhaps reflected in these figures. It is also possible that in the past some male teachers might also have been employed in the high risk professions before becoming teachers, their deaths would therefore be recorded under this, their final profession. This is more likely in higher education. In the Southampton tables the actual PMR of male teachers in higher education is given as 121 and for other male teachers as 57 126. When one considers that these PMRs are formulated from a comparison with other occupations, including high risk ones such as shipyard workers and builders, one can see that male teachers’ deaths are respectively 22 times, and 10 times higher than they would have been if there had been no exposure. It can therefore be concluded that male teachers’ deaths from mesothelioma far exceed the number that one would expect from an occupation where there should be minimal or no asbestos exposure. (Stats 10)

Male teacher deaths from mesothelioma. SOC classification lists 45 male primary and secondary school teachers who died from mesothelioma between 1991 and 2000. In higher and further education a further 48 teachers died, if other teaching professionals and education assistants are included then a total of 97 male teachers died from mesothelioma 131. (Stats 9) Generally male deaths from mesothelioma are considerably greater than those of females. This is not because the male anatomy is more susceptible to mesothelioma, it is because males are more involved in occupations that disturb asbestos fibres, in addition they are more likely to take part in DIY and in consequence are liable to disturb ACMs. Perhaps some of these deaths might be accounted for by asbestos exposure experienced in a former high risk occupation. However what is most relevant is that historically males rather than females normally taught science and technology in schools and further education colleges. In addition the pupils studying science and taking part in workshop activities were more likely to be male.

Teachers' deaths high in comparison with others
Among 900 female occupations, primary and secondary school teachers have the sixth highest number of deaths from mesothelioma The HSE statistics giving occupational mesothelioma deaths lists 900 female Standard Occupational Classification (SOC) occupations. In a ten year period 25 female primary teachers died of mesothelioma and 3 female secondary teachers died. If one compares the mesothelioma deaths amongst all the occupations then female primary and secondary teachers have the sixth highest number of deaths 127. (Primary and secondary teacher numbers have to be combined because of possible errors on death certificates) 128
 

Among 90 female occupational groups teachers and related childcare occupations have the fourth highest PMR from mesothelioma.The 900 SOC occupations are grouped into slightly more than 90 groups of similar occupations. From 1991-2000 among female occupation groups with the greatest number of mesothelioma deaths “Labourers and fitters” and “Textile workers” have the highest PMRs 129. This can be accounted for because of the known asbestos contamination occurring in these occupations. Sales assistants and then teachers/ education assistants/ childcare related occupations are the next greatest. One might question why sales assistants have such a high PMR, however that is not within the direct scope of this paper. The figures are confirmed by the HSE tables which list occupations under the Southampton coding. About 200 occupations are listed with mesothelioma deaths between 1980-2000. Female school teachers’ PMR is also the fourth highest 130. The fact that female teachers rank so high in mesothelioma deaths is remarkable, especially as one considers that each death is the result of asbestos exposure. ( Stats 6,7,8)

US identifies elementary school teachers elevated risk
The disproportionate number of mesothelioma deaths amongst school teachers is not unique to this country. As has been seen the latest American mesothelioma statistics highlight elementary school teachers as having “A significantly elevated mesothelioma mortality.”
   
Explanation of occupational codings.
Southampton codes only list teachers under teachers in higher education and teachers not elsewhere classified (nec). Teachers assistants etc are therefore not included in these totals. The totals for 1981 are also not included because of civil servant industrial action. The Standard Occupational Classification coding (1990) breaks down the occupations into greater detail, but only came into force in 1991. It lists each teaching occupation under separate headings and in two groups:
  • Group 230 Teaching Professionals: University and polytechnic teaching professionals, higher & further education teaching professionals, secondary (and middle school deemed secondary) teaching professionals. Primary (& middle school deemed primary) & nursery teaching professionals, special education teaching professionals, other teaching professionals nec.
  • Group 650 Childcare and related personal services. Playgroup leaders, nursery nurses, educational assistants and other childcare and related occupations nes.

The only difference between the groups is the teacher’s qualifications, the age of the people that they teach, or the disabilities of the children that they teach. Some University, polytechnic, higher and further education teachers will work with adults, however the majority of teachers work with children in classrooms, laboratories, workshops or playgroups. The concern is that too many teachers, classroom assistants and childcare related occupations are dying from asbestos exposure, and each of them has a similar job in as much as they look after children.

   
Total mesothelioma deaths - teachers and related occupations
The Southampton codes list a total of 182 teachers and University lecturers who died of mesothelioma between 1980 and 2000132. (Stats 16) The SOC classifications list a total of 145 teachers, university lecturers and related occupations who died of mesothelioma between 1991 and 2000 133. (Stats 4,9,11)These are the deaths which can be directly attributable to asbestos exposure, however it must not be forgotten that there are other cancers caused by asbestos, but they will not be recorded as such.
   
Increasing teachers' deaths from mesothelioma
The number of teachers dying from mesothelioma has been increasing over the years. The increase in deaths amongst females in primary and secondary education has been some fourfold since 1980 134. Male primary and secondary teacher deaths have more than doubled, and the deaths among males in higher education have increased fourfold 135. (Stats 12,14,15)
   
Comparison of female teachers and nurses
It is useful to make a comparison between female occupations as they are less likely than males to have been involved in any former high risk occupations, and they are also less likely to have carried out DIY. Therefore a comparison of the PMRs from another female occupation can be used to determine whether teachers have been disproportionately exposed to asbestos. Female teachers can be compared with female nurses as both are professions in which a similarly large numbers of females are employed 136. In addition one would imagine that the risk from asbestos exposure in both professions should be minimal. However the statistics show that since 1980 the PMR for female primary and secondary school teachers dying from mesothelioma has been 100 and nurses 50 137. The teachers’ PMR is twice that of nurses. As there is a direct correlation between asbestos exposure and mesothelioma one must conclude that the asbestos exposure amongst teachers has been about twice that of nurses. (Stats 12,13) It can therefore be concluded that compared to a similar profession, a disproportionate number of female school teachers have died from mesothelioma.

 

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