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Quartz in Swedish iron foundries: exposure and cancer risk
Örebro University, School of Science and Technology.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aims of the studies underlying this thesis were to assess the exposure to quartz in Swedish iron foundries and to determine the cancer morbidity for Swedish foundry workers. A cohort of 3,045 foundry workers and a final measurement database of 2,333 number of samples was established.

The exposure measurements showed high levels of respirable quartz, in particular for fettlers and furnace and ladle repair workers with individual 8 hr TWA (GM=0.041 and 0.052 mg/m3; range 0.004-2.1 and 0.0098-0.83 mg/m3). In our database, the quartz concentrations as 8hr TWAs of current and historical data varied between 0.0018 and 4.9 mg/m3, averaging 0.083 mg/m3, with the highest exposures for fettlers (0.087 mg/m3) and furnace and ladle repair workers (0.42 mg/m3). The exposure for workers using respirators assuming full effect when used were assessed quantitatively, revealing workers with actual exposure exceeding the occupational exposure limits.

Overall cancer morbidity was not increased, but the incidence of lung cancer was significantly elevated (SIR 1.61; 95 % CI 1.20-2.12). In the cohort study, significant associations between lung cancer and cumulative quartz exposure were detected for quartz doses of 1-2 mg/m3 * year (SIR 2.88; 95 % CI 1.44-5.16) and >2 mg/m3 * year (SIR 1.68; 95 % CI 1.07- 2.52). These findings were not confirmed in the case-control analysis.

The agreement between the estimated exposure in our early historical model and the development model showed a regression coefficient of 2.42, implying an underestimation of the historical exposure when using the development model data. The corresponding comparison between the development and the validation model based on our survey data showed a B of 0.31, implying an overestimation of present exposures when using data from the validation model.

The main conclusions of the thesis are that certain foundry workers are still exposed to high levels of quartz, and the overall excess lung cancer could not be confirmed in the exposure-response analysis.

Place, publisher, year, edition, pages
Örebro: Örebro universitet , 2012. , 78 p.
Series
Örebro Studies in Environmental Science, ISSN 1650-6278 ; 16
Keyword [en]
Case-control study, crystalline silica, exposure assessment, iron foundry, lung cancer, morbidity, occupational hygiene, respirable quartz
National Category
Earth and Related Environmental Sciences
Research subject
Enviromental Science
Identifiers
URN: urn:nbn:se:oru:diva-20620ISBN: 978-91-7668-837-3 (print)OAI: oai:DiVA.org:oru-20620DiVA: diva2:468922
Public defence
2012-02-10, Bohmanssonsalen, B-huset, Universitetssjukhuset, Örebro, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2011-12-22 Created: 2011-12-22 Last updated: 2017-10-17Bibliographically approved
List of papers
1. Quartz and dust exposure in Swedish iron foundries
Open this publication in new window or tab >>Quartz and dust exposure in Swedish iron foundries
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2009 (English)In: Journal of Occupational and Environmental Hygiene, ISSN 1545-9624, E-ISSN 1545-9632, Vol. 6, no 1, 9-18 p.Article in journal (Refereed) Published
Abstract [en]

Exposure to respirable quartz continues to be a major concern in the Swedish iron foundry industry. Recommendations for reducing the European occupational exposure limit (EU-OEL) to 0.05 mg/m3 and the corresponding ACGIH® threshold limit value (ACGIH-TLV) to 0.025 mg/m3 prompted this exposure survey. Occupational exposure to respirable dust and respirable quartz were determined in 11 Swedish iron foundries, representing different sizes of industrial operation and different manufacturing techniques. In total, 436 respirable dust and 435 respirable quartz exposure measurements associated with all job titles were carried out and are presented as time-weighted averages. Our sampling strategy enabled us to evaluate the use of respirators in certain jobs, thus determining actual exposure. In addition, measurements using real-time dust monitors were made for high exposure jobs. For respirable quartz, 23% of all the measurements exceeded the EU-OEL, and 56% exceeded the ACGIH-TLV. The overall geometric mean (GM) for the quartz levels was 0.028 mg/m3, ranging from 0.003 to 2.1 mg/m3. Fettler and furnace and ladle repair operatives were exposed to the highest levels of both respirable dust (GM = 0.69 and 1.2 mg/m3; range 0.076-31 and 0.25-9.3 mg/m3 and respirable quartz (GM = 0.041 and 0.052 mg/m3; range 0.004-2.1 and 0.0098-0.83 mg/m3. Fettlers often used respirators and their actual quartz exposure was lower (range 0.003-0.21 mg/m3, but in some cases it still exceeded the Swedish OEL (0.1 mg/m3. For furnace and ladle repair operatives, the actual quartz exposure did not exceed the OEL (range 0.003-0.08 mg/m3, but most respirators provided insufficient protection, i.e., factors less than 200. In summary, measurements in Swedish iron foundries revealed high exposures to respirable quartz, in particular for fettlers and furnace and ladle repair workers. The suggested EU-OEL and the ACGIH-TLV were exceeded in, respectively, 23% and 56% of all measurements regardless of the type of foundry. Further work on elimination techniques to reduce quartz concentrations, along with control of personal protection equipment, is essential.

Place, publisher, year, edition, pages
Philadelphia, PA: Taylor & Francis, 2009
Keyword
exposure, iron foundry, quartz; respirators
National Category
Medical and Health Sciences Environmental Health and Occupational Health
Research subject
Occupational and Environmental Medicine
Identifiers
urn:nbn:se:oru:diva-3404 (URN)10.1080/15459620802523943 (DOI)000261508800002 ()18982534 (PubMedID)
Available from: 2008-12-04 Created: 2008-12-04 Last updated: 2017-10-18Bibliographically approved
2. Cancer morbidity and quartz exposure in Swedish iron foundries
Open this publication in new window or tab >>Cancer morbidity and quartz exposure in Swedish iron foundries
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(English)Manuscript (preprint) (Other academic)
Keyword
Cohort study, lung cancer, occupational exposure, respirable silica, smoking habits
National Category
Medical and Health Sciences Environmental Health and Occupational Health
Research subject
Occupational and Environmental Medicine
Identifiers
urn:nbn:se:oru:diva-21292 (URN)
Available from: 2012-01-24 Created: 2012-01-24 Last updated: 2017-10-17Bibliographically approved
3. Exposure assessment and modeling of quartz in Swedish iron foundries for a nested case-control study on lung cancer
Open this publication in new window or tab >>Exposure assessment and modeling of quartz in Swedish iron foundries for a nested case-control study on lung cancer
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2012 (English)In: Journal of Occupational and Environmental Hygiene, ISSN 1545-9624, E-ISSN 1545-9632, Vol. 9, no 2, 110-119 p.Article in journal (Refereed) Published
Abstract [en]

Exposure assessment of quartz in Swedish iron foundries was performed based on historical and present measurement data. To evaluate the exposure response relationship between quartz exposure and lung cancer, we modeled quartz exposure from our database of measurements using determinants job title, time period and company. Based on these modeled exposure data, we conducted a nested case– control evaluation.

In our database, the overall individual daily time-weighted average (TWA) quartz concentrations of current and historical data varied between 0.0018 and 4.9 mg/m3, averaging 0.083 mg/m3. The job titles with mean TWAs for the whole study period exceeding the European Union recommended occupational exposure limit of 0.05 mg/m3 were fettlers (0.087 mg/m3), furnace and ladle repair (0.42 mg/m3) and maintenance (0.054 mg/m3) workers.

The mixed model analysis demonstrated significant determinants on the job level for furnace and ladle repair (β=4.06; 95% CI 2.78-5.93). For all jobs significantly higher exposure levels occurred only during the first time period, 1968-1979 (β=2.08; 95% CI 1.75-2.47), and a decreasing but not significant trend was noted for the three following 10 year time periods up to 2006 (β=1.0, 0.96 and 1, respectively). Two iron foundries had significantly higher quartz concentration levels than the others (β=1.31; 95% CI 1.00-1.71 and β=1.63; 95% CI 1.00-2.65, respectively). The individual cumulative quartz exposure measures were categorized in low, medium and high exposure (0.5-<1, 1-1.9 and ≥2 mg/m3 *years, respectively).

In the nested case-control analysis, we found the highest odds ratios of lung cancer (OR 1.17; 95% CI 0.53-2.55) for the medium exposure group. No dose– response trend or significantly increased risk was determined for our high exposed group (≥2 mg/m3), representing 40 years of exposure at >0.05 mg/m3 of quartz. To conclude, certain foundry workers are still exposed to high levels of quartz, but an increased risk of lung cancer caused by quartz exposure in these Swedish iron foundries could not be confirmed at our exposure levels.

Place, publisher, year, edition, pages
Philadelphia: Taylor & Francis, 2012
Keyword
Exposure modeling, iron foundry, lung cancer, quartz
National Category
Medical and Health Sciences Environmental Health and Occupational Health
Research subject
Occupational and Environmental Medicine
Identifiers
urn:nbn:se:oru:diva-21293 (URN)10.1080/15459624.2011.645397 (DOI)000300962700009 ()22239127 (PubMedID)2-s2.0-84860878860 (Scopus ID)
Funder
AFA Insurance
Note

Funding Abency:

AFA, Stockholm 

Available from: 2012-01-24 Created: 2012-01-24 Last updated: 2017-12-08Bibliographically approved
4. Estimating trends in quartz exposure in Swedish iron foundries: predicting past and present exposures
Open this publication in new window or tab >>Estimating trends in quartz exposure in Swedish iron foundries: predicting past and present exposures
2012 (English)In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 56, no 3, 362-372 p.Article in journal (Refereed) Published
Abstract [en]

Background: Swedish foundries have a long tradition of legally required surveys in the work place that, from the late 1960s onwards, included measurements of quartz. The availability of exposure data spanning almost 40 years presents a unique opportunity to study trends over that time and to evaluate the validity of exposure models based on data from shorter time spans. The aims of this study were (i) to investigate long term trends in quartz exposure over time, (ii) using routinely collected quartz exposure measurements to develop a mathematical model that could predict both historical and current exposure patterns, and (iii) to validate this exposure model with up-to-date measurements from a targeted survey of the industry.

Methods: Eleven foundries, representative of the Swedish iron foundry industry, were divided into three groups based on the size of the companies, i.e. the number of employees. A database containing 2333 quartz exposure measurements for 11 different job descriptionswas used to create three models that covered time periods which reflected different work conditions and production processes: a historical model (1968– 1989), a development model (1990–2004), and a validation model (2005–2006). A linear mixed model for repeated measurements was used to investigate trends over time. In all mixed models, time period, company size, and job title were included as fixed (categorical) determinants of exposure. The within- and between-worker variances were considered to be random effects. A linear regression analysis was erformed to investigate agreement between the models. The average exposure was estimated for each combination of job title and company size.

Results: A large reduction in exposure (51%) was seen between 1968 and 1974 and between 1975 and 1979 (28%). In later periods, quartz exposure was reduced by 8% per 5 years at best. In the first period, employees at smaller companies experienced ~50%higher exposure levels than those at large companies, but these differences became much smaller in later years. The furnace and ladle repair job were associated with the highest exposure, with 3.9–8.0 times the average exposure compared to the lowest exposed group. Without adjusting for this autonomous trend over time, predicting early historical exposures using our development model resulted in a statistically significant regression coefficient of 2.42 (R2 5 0.81), indicating an underestimation of historical exposure levels. Similar patterns were seen for other historical time periods. Comparing our development model with our validation model resulted in a statistically significant regression coefficient of 0.31, indicating an overestimation of current exposure levels.

Conclusion: To investigate long-term trends in quartz exposure over time, overall linear trends can be determined by using mixed model analysis. To create individual exposure measures to predict historical exposures, it is necessary to consider factors such as the time period, type of job, type of company, and company size. The mixed model analysis showed systematic changes in concentration levels, implying that extrapolation of exposure estimates outside the range of years covered by measurements may result in underestimation or overestimation of exposure.

Place, publisher, year, edition, pages
Oxford, United Kingdom: Oxford University Press, 2012
Keyword
Iron foundry, predicting exposures, quartz, time trends
National Category
Medical and Health Sciences Environmental Health and Occupational Health
Research subject
Occupational and Environmental Medicine
Identifiers
urn:nbn:se:oru:diva-21296 (URN)10.1093/annhyg/mer106 (DOI)000302015600011 ()22104319 (PubMedID)2-s2.0-84858671192 (Scopus ID)
Available from: 2012-01-24 Created: 2012-01-24 Last updated: 2017-12-08Bibliographically approved

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