Occupational Medicine 2016;66:106–111 Advance Access publication 28 October 2015 doi:10.1093/occmed/kqv142
UK asbestos imports and mortality due to idiopathic pulmonary fibrosis C. M. Barber1, R. E. Wiggans1, C. Young2 and D. Fishwick1 Centre for Workplace Health, Health and Safety Laboratory, Harpur Hill, Buxton SK17 9JN, UK, 2Mathematical Sciences Unit, Health and Safety Laboratory, Harpur Hill, Buxton SK17 9JN, UK.
1
Correspondence to: C. M. Barber, Centre for Workplace Health, Health and Safety Laboratory, Harpur Hill, Buxton SK17 9JN, UK. Tel: +44 (0)1298 218169; e-mail: [email protected] Background Previous studies have demonstrated that the rising mortality due to mesothelioma and asbestosis can be predicted from historic asbestos usage. Mortality due to idiopathic pulmonary fibrosis (IPF) is also rising, without any apparent explanation. Aims
To compare mortality due to these conditions and examine the relationship between mortality and national asbestos imports.
Methods
Mortality data for IPF and asbestosis in England and Wales were available from the Office for National Statistics. Data for mesothelioma deaths in England and Wales and historic UK asbestos import data were available from the Health & Safety Executive. The numbers of annual deaths due to each condition were plotted separately by gender, against UK asbestos imports 48 years earlier. Linear regression models were constructed.
Results
For mesothelioma and IPF, there was a significant linear relationship between the number of male and female deaths each year and historic UK asbestos imports. For asbestosis mortality, a similar relationship was found for male but not female deaths. The annual numbers of deaths due to asbestosis in both sexes were lower than for IPF and mesothelioma.
Conclusions The strength of the association between IPF mortality and historic asbestos imports was similar to that seen in an established asbestos-related disease, i.e. mesothelioma. This finding could in part be explained by diagnostic difficulties in separating asbestosis from IPF and highlights the need for a more accurate method of assessing lifetime occupational asbestos exposure. Key words
Asbestos; asbestosis; idiopathic pulmonary fibrosis; mesothelioma.
Introduction World Health Organization (WHO) mortality data have established that historic asbestos consumption is a significant predictor of mortality due to long-latency asbestos-related disease [1]. Knowledge of previous asbestos usage has also been utilized to develop models capable of predicting future mortality from asbestosis and mesothelioma in a number of different countries [2–6]. Asbestosis is a form of chronic interstitial lung disease that occurs in a proportion of individuals following prolonged and usually heavy occupational exposure to asbestos [7]. It most commonly occurs several decades after exposure and is more common in men and in older age groups [8]. The main differential diagnosis for asbestosis is idiopathic pulmonary fibrosis (IPF), where a
similar pattern of fibrosis [usual interstitial pneumonitis (UIP)] occurs with no identifiable cause [9]. Differentiating asbestosis from IPF is important, as the former may be eligible for benefits/compensation, whereas the latter may be considered for anti-fibrotic drug treatments [10]. Diagnosis may be challenging, however, as patient recall of previous exposures to asbestos is variable [11], radiological features may be identical [12] and few patients undergo surgical lung biopsy [13]. Mortality due to IPF has risen steadily in the UK over recent decades, with the condition now accounting for approximately ~5000 deaths each year [14]. IPF shares several of the demographic risk factors of asbestosis mortality, yet epidemiological studies of IPF have not identified links with previous asbestos exposure [15]. Certain
© Crown copyright 2015. This Open Access article contains public sector information licensed under the Open Government Licence v2.0 (http://www.nationalarchives.gov.uk/doc/open-government-licence/version/2/).
C. M. BARBER ET AL.: UK ASBESTOS IMPORTS AND IPF 107
occupations have however been linked with an increased risk of IPF in Britain, particularly workers exposed to metal and wood dusts [16,17]. Although the reason for the rising IPF mortality in the UK remains unexplained [14], it has previously been noted to be following a similar pattern to an established asbestos-related disease, i.e. mesothelioma [18]. Given this observation and the difficulties of differentiating idiopathic from asbestos-induced fibrosis, this study aimed to compare IPF, asbestosis and mesothelioma mortality and examine their relation to historic national asbestos imports.
48 years was selected based on a previously developed US asbestosis model [2]. Annual numbers of male and female deaths in England and Wales due to IPF, asbestosis and mesothelioma were plotted for each year, against data for historic UK asbestos imports expressed as hundreds of tonnes. In addition, total annual deaths from mesothelioma and IPF for men and women were plotted separately, and Pearson correlation coefficients calculated. Finally, the total number of deaths per year due to mesothelioma, asbestosis and IPF for men and women was plotted against historic asbestos imports, and regression models constructed.
Methods
Results
This analysis utilized mortality data as published by the Office for National Statistics (ONS) [19], and by the Health & Safety Executive (HSE) [20]. Annual numbers of male and female deaths (England and Wales), where IPF (1962–2012) and asbestosis (1967–2012) were listed as the underlying cause, were requested from the ONS. ICD codes for IPF were used as per the method described by Navaratnam et al. [14]. Asbestosis ICD codes used were ICD8 515.2 asbestosis, ICD9 501 asbestosis and ICD10 J61 pneumoconiosis due to asbestos and other mineral fibres. Annual mortality figures for mesothelioma for Britain were available from 1968 to 2012 from the HSE. These figures are derived from ONS data but include all deaths where mesothelioma was mentioned on the death certificate. Figures for England and Wales were calculated by subtracting Scottish mesothelioma deaths. Total asbestos imports for each year between 1914 and 1965 were calculated by adding annual import data for chrysotile, amosite and croccidolite [21,22]. Where individual annual import data were not available, figures were calculated by linear interpolation. A latent period of
Given the 48-year latent interval selected, the time period 1962–2013 in Figures 1 and 2 corresponds to historic asbestos imports between 1914 and 1965. Total asbestos imports to the UK rose steadily over this time, apart from a fall in the period between 1941 and 1947, during and shortly after the Second World War. Over the period included in the analysis, male mortality due to IPF, mesothelioma and asbestosis rose steadily (Figure 1). The total numbers of male deaths due to IPF and mesothelioma for each year were of a similar magnitude, with a much lower number of deaths attributed to asbestosis. For female mortality (shown in Figure 2), the number of deaths due to IPF and mesothelioma also increased over this period, but there was no increase in deaths due to asbestosis. In contrast to male mortality, the annual number of female deaths due to IPF was consistently higher than deaths due to mesothelioma. The ratio of male deaths directly attributed to asbestosis versus IPF remained relatively constant over the study period, at approximately 1:16 in 1967 and 1:13 in 2012. For female mortality, however, this ratio rose by a factor of ten, from approximately 1:38 in 1967 to 1:381 in 2012.
Figure 1. Annual male mortality due to IPF, mesothelioma and asbestosis in England and Wales. Historic annual UK asbestos imports (as hundreds of tonnes 48 years earlier) are shown for comparison (black line).
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Figure 2. Annual female mortality due to IPF, mesothelioma and asbestosis in England and Wales. Historical annual UK asbestos imports (as hundreds of tonnes 48 years earlier) are shown for comparison (black line).
Figure 3. Number of annual male deaths (England and Wales) due to IPF and mesothelioma between 1968 and 2012.
Annual mortality due to mesothelioma and IPF showed a significant linear relationship for both men and women, with Pearson correlation coefficients of 0.98 (P
UK asbestos imports and mortality due to idiopathic pulmonary fibrosis C. M. Barber1, R. E. Wiggans1, C. Young2 and D. Fishwick1 Centre for Workplace Health, Health and Safety Laboratory, Harpur Hill, Buxton SK17 9JN, UK, 2Mathematical Sciences Unit, Health and Safety Laboratory, Harpur Hill, Buxton SK17 9JN, UK.
1
Correspondence to: C. M. Barber, Centre for Workplace Health, Health and Safety Laboratory, Harpur Hill, Buxton SK17 9JN, UK. Tel: +44 (0)1298 218169; e-mail: [email protected] Background Previous studies have demonstrated that the rising mortality due to mesothelioma and asbestosis can be predicted from historic asbestos usage. Mortality due to idiopathic pulmonary fibrosis (IPF) is also rising, without any apparent explanation. Aims
To compare mortality due to these conditions and examine the relationship between mortality and national asbestos imports.
Methods
Mortality data for IPF and asbestosis in England and Wales were available from the Office for National Statistics. Data for mesothelioma deaths in England and Wales and historic UK asbestos import data were available from the Health & Safety Executive. The numbers of annual deaths due to each condition were plotted separately by gender, against UK asbestos imports 48 years earlier. Linear regression models were constructed.
Results
For mesothelioma and IPF, there was a significant linear relationship between the number of male and female deaths each year and historic UK asbestos imports. For asbestosis mortality, a similar relationship was found for male but not female deaths. The annual numbers of deaths due to asbestosis in both sexes were lower than for IPF and mesothelioma.
Conclusions The strength of the association between IPF mortality and historic asbestos imports was similar to that seen in an established asbestos-related disease, i.e. mesothelioma. This finding could in part be explained by diagnostic difficulties in separating asbestosis from IPF and highlights the need for a more accurate method of assessing lifetime occupational asbestos exposure. Key words
Asbestos; asbestosis; idiopathic pulmonary fibrosis; mesothelioma.
Introduction World Health Organization (WHO) mortality data have established that historic asbestos consumption is a significant predictor of mortality due to long-latency asbestos-related disease [1]. Knowledge of previous asbestos usage has also been utilized to develop models capable of predicting future mortality from asbestosis and mesothelioma in a number of different countries [2–6]. Asbestosis is a form of chronic interstitial lung disease that occurs in a proportion of individuals following prolonged and usually heavy occupational exposure to asbestos [7]. It most commonly occurs several decades after exposure and is more common in men and in older age groups [8]. The main differential diagnosis for asbestosis is idiopathic pulmonary fibrosis (IPF), where a
similar pattern of fibrosis [usual interstitial pneumonitis (UIP)] occurs with no identifiable cause [9]. Differentiating asbestosis from IPF is important, as the former may be eligible for benefits/compensation, whereas the latter may be considered for anti-fibrotic drug treatments [10]. Diagnosis may be challenging, however, as patient recall of previous exposures to asbestos is variable [11], radiological features may be identical [12] and few patients undergo surgical lung biopsy [13]. Mortality due to IPF has risen steadily in the UK over recent decades, with the condition now accounting for approximately ~5000 deaths each year [14]. IPF shares several of the demographic risk factors of asbestosis mortality, yet epidemiological studies of IPF have not identified links with previous asbestos exposure [15]. Certain
© Crown copyright 2015. This Open Access article contains public sector information licensed under the Open Government Licence v2.0 (http://www.nationalarchives.gov.uk/doc/open-government-licence/version/2/).
C. M. BARBER ET AL.: UK ASBESTOS IMPORTS AND IPF 107
occupations have however been linked with an increased risk of IPF in Britain, particularly workers exposed to metal and wood dusts [16,17]. Although the reason for the rising IPF mortality in the UK remains unexplained [14], it has previously been noted to be following a similar pattern to an established asbestos-related disease, i.e. mesothelioma [18]. Given this observation and the difficulties of differentiating idiopathic from asbestos-induced fibrosis, this study aimed to compare IPF, asbestosis and mesothelioma mortality and examine their relation to historic national asbestos imports.
48 years was selected based on a previously developed US asbestosis model [2]. Annual numbers of male and female deaths in England and Wales due to IPF, asbestosis and mesothelioma were plotted for each year, against data for historic UK asbestos imports expressed as hundreds of tonnes. In addition, total annual deaths from mesothelioma and IPF for men and women were plotted separately, and Pearson correlation coefficients calculated. Finally, the total number of deaths per year due to mesothelioma, asbestosis and IPF for men and women was plotted against historic asbestos imports, and regression models constructed.
Methods
Results
This analysis utilized mortality data as published by the Office for National Statistics (ONS) [19], and by the Health & Safety Executive (HSE) [20]. Annual numbers of male and female deaths (England and Wales), where IPF (1962–2012) and asbestosis (1967–2012) were listed as the underlying cause, were requested from the ONS. ICD codes for IPF were used as per the method described by Navaratnam et al. [14]. Asbestosis ICD codes used were ICD8 515.2 asbestosis, ICD9 501 asbestosis and ICD10 J61 pneumoconiosis due to asbestos and other mineral fibres. Annual mortality figures for mesothelioma for Britain were available from 1968 to 2012 from the HSE. These figures are derived from ONS data but include all deaths where mesothelioma was mentioned on the death certificate. Figures for England and Wales were calculated by subtracting Scottish mesothelioma deaths. Total asbestos imports for each year between 1914 and 1965 were calculated by adding annual import data for chrysotile, amosite and croccidolite [21,22]. Where individual annual import data were not available, figures were calculated by linear interpolation. A latent period of
Given the 48-year latent interval selected, the time period 1962–2013 in Figures 1 and 2 corresponds to historic asbestos imports between 1914 and 1965. Total asbestos imports to the UK rose steadily over this time, apart from a fall in the period between 1941 and 1947, during and shortly after the Second World War. Over the period included in the analysis, male mortality due to IPF, mesothelioma and asbestosis rose steadily (Figure 1). The total numbers of male deaths due to IPF and mesothelioma for each year were of a similar magnitude, with a much lower number of deaths attributed to asbestosis. For female mortality (shown in Figure 2), the number of deaths due to IPF and mesothelioma also increased over this period, but there was no increase in deaths due to asbestosis. In contrast to male mortality, the annual number of female deaths due to IPF was consistently higher than deaths due to mesothelioma. The ratio of male deaths directly attributed to asbestosis versus IPF remained relatively constant over the study period, at approximately 1:16 in 1967 and 1:13 in 2012. For female mortality, however, this ratio rose by a factor of ten, from approximately 1:38 in 1967 to 1:381 in 2012.
Figure 1. Annual male mortality due to IPF, mesothelioma and asbestosis in England and Wales. Historic annual UK asbestos imports (as hundreds of tonnes 48 years earlier) are shown for comparison (black line).
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Figure 2. Annual female mortality due to IPF, mesothelioma and asbestosis in England and Wales. Historical annual UK asbestos imports (as hundreds of tonnes 48 years earlier) are shown for comparison (black line).
Figure 3. Number of annual male deaths (England and Wales) due to IPF and mesothelioma between 1968 and 2012.
Annual mortality due to mesothelioma and IPF showed a significant linear relationship for both men and women, with Pearson correlation coefficients of 0.98 (P
