# Portland Cement Dust

Hazard assessment document

EH75/7FOREWORD

This Hazard Assessment Document has been published by the UK Health

and Safety Executive (HSE). It is aimed at a technical a udience and reports

on the scientific information which underpins the hazard assessment of a

specific substance.

In Great Britain, substances which c ause harm to health are subject to the

Control of Substances Hazardous to Health Regulations (COSHH) 2002 (as

amended). The Regulations require employer s to prevent or, if that is not

reasonably practicable, adequately contro l employees’ exposure to hazardous

substances.

Hazard Assessment Documents are produc ed to facilitate the development of

HSE’s regulatory position on a specific health-related issue, which may relate

to an individual hazardous substance, or may involve consideration of more

general issues related to chemicals and ill health. The documents in this

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series address issues which involve c onsideration of occupational exposure

and risk:

• Exposure Assessment Document – EH74 series;

• Risk Assessment Document – EH72 series.

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and risk management issues, including recommendations for occupational

exposure limits (OELs) and other as pects of occupational health risk

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3Contents Page

1. Summary 6

2. Introduction 7

3. The Health Effects Li terature 9

3.1 Effects of single exposure 9

3.2 Irritation 10

3.3 Skin sensitisation 10

3.4 Effects of repeated ex posure to cement dust 12

3.4.1 Recent studies of non-malignant respiratory 12 disease in workers with long-term exposure to

cement dust

3.4.2 Mortality and cancer studies involving workers 28 with long-term exposure to cement dust

4. References 46

Table 1 Summary of recent studies of non-malignant respiratory 51 disease in workers with long-term exposure to cement dust

Table 2 Summary of mortality and cancer morbidity studies in 52 cement manufacturing workers or masons

Table 3 Summary of German case control studies for cancers 53 of the oral cavity, pharynx and larynxCI GLOSSARY

ATS American Thoracic Society
Confidence interval COPD Chronic obstructive lung disease FEF Forced expiratory flow FEV1 Forced expiratory volume in one second FVC Forced vital capacity MRC Medical Research Council (UK) MVV Maximum voluntary ventilation
OR Odds ratio PEFR Peak expiratory flow rate

RR Relative risk
SD Standard deviation of the mean
SE Standard error of the mean
SIR Standardised incidence ratio SMR Standardised mortality ratio TWA Time weighted average VC Vital capacity WHO World Health Organization

51. SUMMARY

This hazard assessment updates the health effects sections of an earlier HSE review of Portland cement (HSE 1994). T he latter is taken to represent an

accurate assessment of t he literature available up to 1991. This assessment

concentrates on the evidence for non -malignant respiratory disease and carcinogenicity. The primary literat ure on skin sensitisation has not been reviewed because the potential for cement to cause such reactions, due to the presence of hexavalent chromium, has been established by other reviews. Toxicological endpoints such as reproductive toxicity and mutagenicity have

not been considered because there are no data.

Concerning non-malignant respiratory disease, HSE (1994) noted evidence that repeated exposure to Portland cement has produced chronic bronchitis and impaired pulmonary function, but firm conclusions could not be drawn

because of limitations of the avail able studies. The effects of long-term exposure remain poorly studied, particu larly because there are no longitudinal prospective studies in workers exposed to cement. However, many of the 15 recent studies, all conducted outside of the UK, provid e evidence of the presence of respiratory problems among ce ment factory work ers, consistent
with the earlier literature. Ov erall, the pattern of evidence clearly indicates that occupational exposure to cement dust has produced deficits in respiratory function. However, the evidence available at the present time is insufficient to establish with any confidence the dose-resp onse relationship for these effects.

HSE (1994) concluded t hat there was no convincing evidence for an increased incidence of any site-specific cancer resulting from cement exposure, but acknowledged that the data available at that time were not consistently and reassuringly negative. Since the early 1990s, a number of relevant cancer cohort and case control studies have been published, conducted in groups exposed to cement ei ther through employ ment in cement

factories or in the construction i ndustry. Among these and earlier studies,

increased incidences of cancers at se veral sites (stomach, lungs, colon, pharynx and larynx) were noted, but ta king account of limitations in the strength of the observed associations, it is concluded that a causal

association between Portland cement exposure and cancer has not been established. Nevertheless, the findings of the recent studies reviewed in this document maintain the uncertainty conc erning a possible risk of cancer raised by the earlier data reviewed by HSE (1994).

62. INTRODUCTION

This hazard assessment document updates the health effects sections of an
earlier HSE review of Portland cement (HSE 1994). The latter is taken to represent an accurate assessment of the literature available up to 1991. Consequently this hazard assessment concentrates mainly on literature published after this time, although cert ain pre-1991 studies are considered in some detail where they help with the inte rpretation of the recent literature. A copy of the earlier HSE (1994) review is provided as Annex 2 to the
WATCH/2005/03.

There were two reasons for producing th is updating document. Firstly, workrelated chronic obstructive pulmonary di sease (COPD) is a priority within HSE’s Occupational Respiratory Disease (ORD) sub-programme. The evidence-base for this sub-programme indicates that occupational exposure to dusts in general leads to an increased risk of COPD. Cement dust is a particularly alkaline and i rritant dust, and might therefore be considered to pose a greater risk of resp iratory tract damage than m any other poorly soluble dusts (generically often referred to as “low toxicity dusts”). The HSE (1994)

review described evidence for an increased risk of chronic bronchitis and impairment of pulmonary function (cons istent with COPD) in cement dust exposed workers, but there wa s a lack of data on dose-response relationships. Hence, one reason for undertaking this updating assessment was to see whether the scientific literature on cement dust published over the last 10 years is now better able to characterise the risks of COPD, and consequently to help determine whet her or not cement dust should be regarded as a particular priority for action within HSE’s ORD sub-programme.

In addition, it has been drawn to the att ention of HSE that in recent years a

number of case-control studies have been published suggesting that exposure to cement dust may be a cause of laryngeal and pharyngeal cancer. It was felt important to examine the evidence from these studies particularly as the
earlier HSE review of Portland cement (HSE 1994) noted that the evidence for carcinogenicity with cement dust was not reassuringly negative, albeit largely

based on concerns for stomach cancer . Given the widespread occupational exposure to cement dust, it was felt important that HSE develop an updated position in relation to carcinogenicity.

Annex 1 provides a detailed explanati on of the composition and manufacture of Portland cement. In brief, Portl and cement is produced by crushing and grinding calcareous materials (e.g. limestone, chalk) and argillaceous materials (e.g. clay, shale), as a wet slurry or in a dry state. The mixture is calcined in a rotary kiln and the result ing clinker is finely ground. The product is composed largely of calcium silica tes, aluminates, and alumino-ferrites. Other constituents are then added, depending on the desired concrete properties.

Hexavalent chromium (Cr (VI)) can be present in cement. The sources of chromium are in the raw materials, refr actory bricks in the kiln and chromium

7steel grinders. Because of concerns about Cr (VI) sensitisation (see section 2.3), during recent years several countri es have introduced measures to limit the amount of Cr (VI) in cement products. This can be achieved by the addition of ferrous sulphate to cement, wh ich transforms Cr (VI) to form Cr (III) compounds. In 2003 the European Commissi on introduced new legislation to restrict the marketing and use thr oughout the EU of cement products containing soluble Cr (VI) at a concentration of more than 2 ppm.

This document focuses mainly on the evidence for non-malignant respiratory disease and carcinogenicity. Studi es published between 1990 and 2004 were

identified from a literatur e search using TOXLINE and PubMed, or from report reference lists. All relevant reports hav e been critically apprai sed. The primary

literature on skin sensit isation was not review ed because the hazardous properties of cement in relation to this adverse health effect had been established in the pre-1991 literature, and the primary literature has been the subject of two very recent critical revi ews (summarised in section 3.3). Other toxicological endpoints such as reproduc tive toxicity and mutagenicity have

not been considered.

Information on the adverse health e ffects of cement dust comes from

observations of its effects in humans . As noted in the earlier HSE (1994) review, animal data are extremely limited in terms of their scope and quality and do not provide any usef ul information.

A number of the available epidemiology studies were conducted in Portland cement production plant workers. It is noted that thes e workers can be exposed to the raw materials of cem ent production, which include limestone, chalk, clay and shale, to clinker, as well as to Portland cement dust. The exact nature of the dust exposures experienc ed by cement plant workers has not been characterised in any of the st udies. Consequently, one cannot exclude the possibility that any observed ad verse health may have been due, at least in part, to the raw materials and interm ediates of cement production. Among the available epidemiologica l studies, dust exposures have been expressed either in terms of respirable dust, or “tot al dust”, or both. This raises two issues, one concerning the ratio between total and respirable dust (given that cement dust is very fine and one might expect a high proportion of the total dust to be respirable), and the other concerning t he meaning of “total” dust. In the study of Noor et al. (2000), the ratio of total to respirable dust was reported as 8.5 mg.m -3 to 5.7 mg.m -3 . In contrast, in the st udy of Fell et al., the ratio of total to respirable dust was 7.4 mg.m -3 to 0.9 mg.m -3 . The differences in these ratios may be a consequence of measuring dust at different stages of the manufacturing process. One might ex pect a higher propor tion of respirable dust at the later stages of the manufacturing proce ss as opposed to the earlier stages where the raw materials are handled.

It should be noted that the metrics “tot al” and “total inhalable” dust are not equivalent. In many countries, “total dust” is measured using the NIOSH

method that involves a 37 mm closed face cassette. This is known to under sample for “inhalable dust” as meas ured using the IOM sampler (25 mm forward facing cassette). Although not generally specified, it is likely that the

8“total” dust levels reported in t he studies on cement dust refer to
measurements taken with the NIOSH method, and the results will not be equivalent to the UK “total inhalable dust” metric. Overall therefore, the exposure data reported in the following studies need to be interpreted with

care.

3. THE HEALTH EFFECTS LITERATURE

3.1 Effects of single exposure

HSE (1994) reported that there were no data on the effects of a single exposure to cement by rele vant routes of exposure.

Only one recent study looking at short- term effects of cement exposure was identified. Changes in pulmonary function during a work shift were investigated in workers at three Portl and cement factories in Saudi Arabia (Ali et al. 1998). From the payrolls, 150 exposed male workers were selected randomly for the study, in a manner that ensured that all production areas were represented. Their mean age (± SE) was 38.0 ± 0.8 years. As an unexposed control group, 355 male wo rkers were randomly chosen from among administrative staff in the cement, ammonia, petrochemical and asbestos industries. The control group was slightly younger, with a mean age of 34.3 ± 0.5, and their ethnicity was Arab (68%), Indian subcontinent (22%) and South East Asia (9%). Personal information was collected byquestionnaire. The proportion of current smokers, ex-smokers and nonsmokers was similar in the control and exposed groups. Respirable dust was measured using a gravimetric method for a total of 97 samples collected from various production areas; the report does not state the sampling time or whether these were personal or stat ic samples. Spirometry was conduced immediately before and after the morning shift. The hi ghest values from three acceptable expirations for FEV 1 , FVC and FEF 25-75% were recorded and the

FEV 1 /FVC ratio was calculated.

The geometric mean concentration (± SD) of respirable dust ranged from 20 ± 1 mg.m -3 in the quarry to 7 ± 2 mg.m -3 in the kiln area. Spirometry data were reported as mean cross-shift changes. The spirometry readings did not appear to have been adjusted for height. Reductions in FEV 1 , FEV 1 /FVC ratio

and FEF 25-75% occurring during the workshift were significantly greater in the exposed workers. For example, the mean (± SE) reduction in FEV 1 was 0.022 ± 0.008 l for the control group, compar ed with 0.077 ± 0.011 l for the exposed group. For FEV 1 /FVC the mean reduction was 0.011 ± 0.165% and 1.316 ± 0.319% for the control and exposed group. Regression analysis demonstrated no relationship between cross-shi ft pulmonary changes and age or smoking

status.

The results of this study suggest t hat bronchoconstriction had occurred during

the workshift for the cement workers, who were exposed to relatively high dust concentrations. The health significance of this effect is uncertain.

93.2 Irritation

HSE (1994) concluded t hat cement has irritant and corrosive properties, especially when wet, towards the skin. Al so, it was concluded that due to its alkalinity, moistened cement would also produce eye irritation. As these properties of ce ment are well established, no further evaluation of

the literature has been conducted for t hese adverse health effects in the present review.

Portland cement is generally considered to be a respiratory tract irritant, although there are no data on this aspect in the scientific literature.

3.3 Sensitisation

HSE (1994) stated, based on a review of the pre-1979 literature (Fleetwood and Soutar 1979), ‘that there have been m any cases of cement dermatitis appearing to arise as a result of skin sensitisation to hexavalent chromium (Cr(VI)) in cement’. Concerns for sensit isation relate in the main to contact

with the wet cement.

Recently the National Inst itute of Occupational He alth, Norway (NIOH, 2003)

conducted a detailed critical review of the literature, to address these questions:

1. Does Cr(VI) in wet cement cause allergic dermatitis (skin sensitisation) in construction workers?

2. Is there any causal associati on between the reduction of Cr(VI) in cement and the occurrence of allergic dermatitis?

Twenty four papers published between 1975 and 2001 were systematically

reviewed. These were selected as studi es of chromate allergy in humans, especially those involving construction workers, which included the conduct of patch tests for chromate allergy. Most of the investigations were crosssectional studies based on patients att ending dermatology clinics, in the general population, or in groups of construction workers. Some studies provided limited comparative informa tion on the prevalence of Cr(VI) sensitisation in groups of workers exposed to cement with ‘high’ and ‘low’ (less than 2 ppm) Cr(VI) content, conducted in countries where the practice of reducing the Cr(VI) content of cement by the addition of ferrous sulphate has

been introduced.

All the studies reviewed were consi dered by NIOH to have significant limitations, notably the absence of expos ure characterisation, problems with the chromate allergy diagnosis, subjec t selection bias and the lack of prospective follow-up. Nevertheless, t he reviewers identified a consistently high prevalence of Cr(VI) allergy in studi es of construction workers. Also, in general population studies, t he prevalence of allergy was found to be higher in

construction workers than in othe r occupational groups. Furthermore, analyses of patients attending dermatology clinics with a diagnosis of chromate allergy revealed a high pr oportion of patients with occupations involving contact with cement.

10In view of the consistency and strength of the associations it was concluded that, despite their limitations, the avail able studies supported the hypothesis of a causal relationship between Cr(VI) in wet cement and allergic contact

dermatitis in construction workers.

In answer to the second question, it was concluded that there is insufficient

information to decide if there is a caus al association between the reduction of Cr(VI) in cement and a reduced occurrenc e of allergic dermatitis. However, the information that is currently ava ilable supports such a relationship. Furthermore, it is biologically plausibl e that that a reduction in exposure to Cr(VI) will lead to a lower risk of a llergic contact dermatitis.

Recently the European Commission’s Sc ientific Committee on Toxicology, Ecotoxicology and the Environment (SCT EE, now the Scientific Committee on Health and Environmental Risks) expre ssed an opinion of the risks to health from Cr(VI) in cement (European Co mmission, 2002). On the basis of a selective review of the published liter ature, SCTEE concluded that Cr(VI) compounds in cement induce sensitis ation and cause serious allergic

reactions in construction workers. Also they concluded that water-soluble Cr(VI) compounds penetrate the skin to a much greater extent than the less water-soluble Cr (III) compounds, and that Cr(VI) readily penetrates wet leather gloves. SCTEE also concluded that, based on studies in Denmark (Avenstorp, 1989a,b, 1991, 1992), a reducti on of Cr(VI) compounds in cement to less than 2 ppm will reduce the prevalenc e of allergic cement eczema in workers, and will reduce the risk of becoming sensitised to chromate. They also emphasised that educat ion and the use of personal protective measures would also contribute to a lower frequen cy of skin sensitisation due to Cr(VI).

Subsequently the European Commission introduced new legislation, through an amendment (2003/53/EC ) to the Marketing and Use Directive (76/769/EEC), to restrict the mark eting and use of cement and cement containing preparations where the level of soluble Cr(VI) is more than 2 ppm.

Overall, it can be concluded that contact with wet cement can cause sensitisation reactions to Cr(VI) in t he cement and, though not proven, is likely that reducing the Cr(VI) content of cement will reduce the risks of Cr(VI)

sensitisation reactions in work ers who have contact with cement.

113.4 Effects of repeated exposure to cement dust

3.4.1 Recent studies of non-malignant respiratory disease in workers with long-term exposure to cement dust

HSE (1994) noted evidence that repeat ed exposure of humans to Portland cement has produced rhinitis, chronic productive cough (chronic bronchitis), slight abnormalities on chest radiogr aphy and impaired pulmonary function. However, it was considered that the quality of studies indicating adverse effects on pulmonary function was such that the evidenc e for a true effect of

cement dust is inconclusive. From t he limited exposure data available, and from subjective descriptions of worki ng conditions, the respiratory effects appeared to be associated with very dusty working conditions. Although no firm conclusion could be drawn about the dose-response relationship for the respiratory effects, attent ion was drawn to several studies which reported no significant effects associated with airbor ne concentrations of cement dust of

2.9 mg.m -3 total dust and 0.57 mg.m -3 respirable dust (geometric means), up to 5 mg.m -3 total dust and 1.1 mg.m -3 respirable dust, or 2-7.8 mg.m -3 total dust and 1-2.2 mg.m -3 respirable dust.

The literature search conducted in 2004 identified a number of recently published cross sectional studies, together with one retrospective cohort study, of non-malignant respiratory dis ease conducted in workers at cement production plants. In 11 studies, pul monary function testing was conducted and information on the presence of self -reported respiratory symptoms was usually collected. Pulmonary function te sting was by spirometry, except for one study that used a peak flow meter. On e cross sectional study investigated workers using chest radiography. A further 3 studies in cement production workers looked only at self reported respiratory symptoms. All these 15 studies are appraised below, and summarised in Table 1.

Two general health surveys of populat ions of construction workers are available (Petersen and Zelling 1998 and Ar ndt et al. 1996) but these studies do not provide any information on health that can be related to cement dust exposure so these studies were not included in this review.

3.4.1.1 Retrospective cohort study, which included pulmonary function testing

Fell et al. (2003) conducted a retrospective cohort study in 119 Norwegian cement factory workers. A respiratory questionnaire was administered and spirometry was
conducted. Current dust level measurements were available and a semi-quantitative cumulative exposure matrix was developed. The study showed no differences in the respiratory health of the cement workers exposed to average respirable dust levels of at least 1 mg.m -3 when compared with matched blue-collar controls

In a recent retrospective cohort study , pulmonary function and the presence of respiratory symptoms were investigat ed in a group of Norwegian Portland cement factory workers (Fell et al. 2003). The investigation was conducted in 1998 and 1999. The study population comprised men born between 1918 and 1938 who had worked at a particular cement -producing factory for at least one year; presumably most of the study popul ation were retired. A total of 226

12workers fulfilling these criter ia were identified, of which 148 were still alive. No

information was available on the cause of death of those who had died. After exclusions due to white collar work, work place exposures to paint or welding fume, medical conditions unrelated to wo rk that would affect ability to undergo spirometry testing, refusal to participat e or not being contactable, 119 workers were available for the study. Only 4 work ers refused to participate. They had a mean age of 69 years, and a me an of 21.8 years exposure to cement dust. As controls, a group of 94 men bor n between 1918 and 1938 and who had worked at an ammonia plant for at least one year were identified; 63 were still alive at the time of the study. The ammonia plant was located about 10 km from the cement plant. It used closed processes, so the workers were not exposed to ammonia. None of the control workers had ever experienced exposure to ammonia at levels suffi cient to cause symptoms of sensory

irritation. After exclusions due to refusal to participate or not being contactable, 50 controls, of m ean age 67 years were available for investigation. The percentage of deceas ed workers in the cement workers and controls was similar, at about 35%. The proportion of current smokers was slightly higher among the cement work ers (35%) than the controls (26%).

Previous dust exposures for particular work processes were estimated from documented information on changes in work practice and from detailed interviews with a subgroup of workers. Four levels of historical exposure were established, and assigned semiquantitativ e exposure numbers. Cumulative exposure indices were calculated fo r each worker for an exposure-response analysis. Contemporary dust exposure was measured by personal sampling, over 8 hour periods on three days of work; 20 person-related measurements were conducted. Silica levels were measured in the three samples showing the highest amounts of dust. Inform ation on respirat ory symptoms was gathered, using a Norwegian modifica tion of the MRC questionnaire, answered at home. Also, information on job history, cem ent dust exposure level estimates, asbestos exposure and smoking habits were gathered. Spirometry was conducted in acco rdance with ATS guidelines by an investigator who was only ‘partially’ b linded to exposure status. A diagnosis of COPD was made in subjects with a hi story of chronic cough, phlegm when coughing, breathlessness and/or wheezing and also with FEV 1 /FVC ratio of

less than 70%.

In the contemporary workplace air sa mples the mean concentration for total dust was 7.4 mg.m -3 (range 0.4 - 53.7 mg.m -3 ) and for respirable dust 0.91

mg.m -3 (all respirable dust measurem ents were below the Norwegian exposure limit of 5 mg.m -3 ). Silica was not detected in two samples and was

0.06 mg.m -3 in the third sample, below the local limit. The prevalence of respiratory symptoms was slightly higher in the cement workers, and positively associated with cumulative exposure index for three of the symptoms; however, there we re no statistically significant differences between the control and exposed workers. There we re no significant di fferences for the spirometry parameters, after adjustment for age, height, tobacco use and asbestos exposure. For the controls and exposed workers, FVC was 86 and 89% of predicted (according to age, height and gender), FEV 1 was 85 and 90% of predicted and FEV 1/ FVC ratio was 73 and 74%, respectively. Among

13the cement workers the spirometry results were similar for the workers within the highest and lowest cumulative expos ure quartiles. The prevalence of COPD was 14% for controls and 14.3% for exposed workers.

Overall, this study showed no differences in the respiratory health of surviving workers exposed to cement plan t dust and a comparable group of nonexposed workers. This study included an assessment of workers who had left the cement plant, so the potential for se lection bias due to the exclusion of individuals who may have left the cement plant because of work related illhealth was reduced. However, no info rmation on the causes of death among

the 35% of workers who were deceased wa s available so the possibility of selection bias resulting from the ex clusion of individua ls who died of respiratory disease cannot be excluded. Nevertheless, the percentage of deaths in the two groups was similar s uggesting that if selection bias was present it was minimal. A weakness of the semi-quantit ative dose-response

assessment is that this relied on estima tes of cumulative exposure in the

absence of historical dust measuremen t. Inaccuracies in the exposure estimation would result in a tendency for the masking any exposure-response relationship, if present.

One limitation of this study is that it is not possible to dr aw firm conclusions

about the maximum airborne concentration of cement plant dust that would not be associated with adverse respir atory health because of the absence historical quantitative expo sure measurements. Nevertheless, if it is assumed that historical exposures were at l east as high as contemporary exposures, the study provides reassurance that t he control of cement dust levels to around 1 mg.m -3 (respirable dust) will provid e protection against adverse effects on respiratory health.

3.4.1.2 Cross sectional studies which included pulmonary testing

Mwaiselage et al. (2004) studied 115 Tanzanian cement factory workers. Pulmonary function was investigated by spirometry and peak flow measurement. Current total dust exposure measurements were available, from which cumulative exposures were estimated. Lung function was poorer in the occupational goups with current mean dust exposure of 3.2 mg.m -3 and above (cumulative dust exposure 36 mg.m -3 year and above).. The risk of developing a notable obs tructive impairment, represented by a

FEV 1 /FVC ratio <0.7, was significantly increased for cumulative dust exposures in excess of 300 mg.m -3 year.

In a recent study, pulmonary function wa s investigated in male workers at

Tanzanian Portland cement factory (Mwaiselage et al. 2004). The exposed study population was all 126 production workers at t he plant. A control group was made up of all 88 maintenance workers and 32 randomly selected

administrative workers. After exclusi ons because of refusal to participate (about 4%), unsatisfactory spiromet ry performance, physician diagnosed asthma or the presence of other di seases that could affect pulmonary function, 115 exposed subjec ts and 102 controls were available for the final analysis. The mean duration of employ ment for the exposed group was 12 years and for the controls 15 years. In formation on personal characteristics, smoking, use of personal protective equipment and occupational history were

14obtained by standardised questionnaire. Sp irometry was conducted during the morning, and to ATS guidelines. PEFR was measured by Vitalograph peak

flow meter. FEV 1 , FVC and PEFR were expressed as absolute values and as % of predicted with reference to age and height adjusted values for the male Tanzanian population. A person was consid ered to have airflow limitation if

the FEV 1 /FVC ratio was <0.7. A contem porary dust exposure assessment was based on 120 full-shift personal samp les of total dust, collected from 52 exposed and 28 control subjects. Dust exposures were also expressed for each occupational group as a cumulative mean, calculated as the product of the geometric mean concentration and t he number of years worked in the particular group.

Smoking was more prevalent in t he exposed group, with 32% being eversmokers, compared with 25% among cont rols. Mean cumulative total dust exposure was 11 mg.m -3 year (range 0.3-38) for the controls and 69 mg.m -3
year (range 3-926) for the exposed gr oup. Approximately 30% of production and maintenance works reported wearing disposable protective face masks regularly, although the quality and effe ctiveness of these masks could not be determined. The report stated that t here was no correlation between face mask use and lung function, but no data were presented. A summary of the dust exposure and lung function data is presented in following table. FEV 1 % and FEV 1 /FVC ratio was much lower and the prevalence of airways obstruction was higher in the occupational goups with current mean dust exposure of 3.2 mg.m -3 and above (cumulative 36 mg.m -3
and above).

Admin Mainten Raw mill Kiln Cement Crusher Packing Crane (n=19) -ance (n=17) (n=26) mill (n=18) (n=30) (n=13) (n=83) (n=11)

Mean current 0.3 1 1.8 2.9 3.2 13.5 21.3 38.6

total dust (0-2) (0-10) (1-4) (1-10) (1-8) (0-63) (23-230) (8-140)

exposure
mg.m -1 (range)

Mean 4 14 21 12 36 158 230 378

cumulative total (0-10) (1-38) (9-43) (3-87) (22-74) (41-405) (43-639) (77-926) dust exposure

mg.m -1 (range) Smoking (pack 3.4 2.4 1.7 0.9 3.0 3.2 1.9 1.4 years)

FEV 1 % 97 ± 15 100 ± 12 96 ± 16 91 ± 10 77 ± 8 79 ± 14 74 ± 14 78 ± 12 predicted (±SD)

FEV 1 /FVC 0.86 ± 0.87 ± 0.90 ± 0.81 ± 0.75 ± 0.74 ± 0.72 ± 0.72 ± (±SD) 0.12 0.07 0.1 0.06 0.0.05 0.09 0.10 0.06

Number with 1 (5%) 5 (6%) 1 (7%) 1 (4%) 2 (18%) 5 (28%) 14 (47%) 3 (23%)

airflow limitation (%)

A statistical comparison of the results for all exposed workers were compared
with the maintenance/administrative controls. Percentage predicted FEV 1 for the exposed group (mean ± SD, 82% ± 15) was lower than for controls (99% ±

1512). Similarly, FEV 1 /FVC for the exposed group (0.77 ± 0.1) was lower than for controls (0.87 ± 0.1), as was PEFR (80% ± 5 vs. 88% ± 7). These differences were statistically significan t. Similar differences were observed for comparisons between ever smokers of the exposed and control groups (after adjusting for number of packs smoked) and never smokers of the exposed and control groups. Linear regression analysis, taking account of height, age and smoking, showed a negative corre lation between cumulative dust exposure and the following lung function parameters: FEV 1 , FVC, FEV 1 /FVC

ratio and PEF. . The OR relating to FEV 1 /FVC ratio <0.7 for o ccupational groups in the cumulative exposure band 100-300 mg.m -3 year was 1.6 (95% CI 0.5-5.1) and for >300 mg.m -3 year was 9.9 (95% CI 3.5-27. 8), after adjustment for age and smoking.

To conclude, this study demonstrated reduced lung function in cement production workers in comparison with a control group with relatively low dust exposure. A strength of this study is that a meaningful analysis for doseresponse relationships was possible bec ause subgroups with very contrasting dust exposure levels were identified. Th is analysis demonstrated that lung function was poorer in the occupational goups with current mean dust exposure of 3.2 mg.m -3 and above (cumulative dust exposure 36 mg.m -3 year and above). and that the risk of develo ping a notable obstructive impairment (i.e. represented by a FEV 1 /FVC ratio <0.7) was significantly increased for cumulative total dust exposures in excess of 300 mg.m -3 year. A weakness of this study is that only contemporary exposure data were available and so the reliability of the cumulative exposure estimates is uncertain. The authors

stated that conditions at the factory and production capacity had changed little since opening in 1965, and they considered it was reasonable to assume that dust exposure levels had remained constant, but questions still remain. The report did not mention whether workers changed jobs within the factory; if this did occur, then exposure group misclassification is possible, which would have the effect of masking a dose response relationship. Overall, this study provided evidence of an association between reduced lung function and current total dust exposures in excess of 3 mg.m -3 and an obstructive impairment associated with cumulative cement exposures likely to be in excess 300 mg.m -3 year.

Laraqui Hossini et al. (2002) investigated the respiratory health of 280 Moroccan cement factory workers by respiratory questionnaire and spirometry. No dust exposure measurements were taken, but levels were described as being relatively high. There was a higher prevalence of respiratory symptoms and minor spirometry deficits among the cement workers, compared with controls.

Pulmonary function and the presence of respiratory symptoms were investigated in workers at a Moroccan cement factory (Laraqui Hossini et al. 2002). The study population was 280 work ers exposed to cement dust, of mean (± SD) age 41 ± 6 years and duration of employment 14 ± 4 years. As a control group, 73 non-exposed administrative workers from the same factory were recruited, of mean age and duration of employment of 37 ± 7 and 13 ± 4 years, respectively. Recruitment met hods were not described. All exposed and control subjects had been employed at the factory for at least 2 years,

16and none were found with re spiratory or cardiac symptoms at a preemployment medical exam ination. The proportion of current, ex- and nonsmokers in the two groups was similar. Demographic information and medical histories were obtained using a standar dised questionnaire based on those of
the MRC and WHO. Chronic bronchitis was defined as productive cough for

at least 3 months of the year, for at least 2 years. Respiratory function was assessed by spirometry, using standard methods. The highest values from three expirations for FVC and FEV 1 were recorded and FEV 1 /FVC ratio was

calculated. Workers with def icits were graded as havin g an ‘alveolar’, slight (FEV 1 71-80% of predicted), moderate (FEV 1 61-70% of predicted), serious (FEV 1 41-60% of predicted) or severe (FEV 1 below 40% of predicted) deficit according to an official French gover nment grading system. Cement plant dust exposure for the exposed group was gr aded in a semi-quantitative manner as low, moderate and high, depending on the job within the plant.

Dust concentration in the workplace wa s not measured, but in the crushing shop, production plant and packing areas the concentration was such that vision was impeded and dust was depos ited on hair and clothing. The prevalence of respiratory symptoms wa s higher among the exposed workers, with 65% reporting symptom s compared with 35% of controls. Most common symptoms were coughing, phlegm, dys pnoea and rhinitis. Approximately 30% of exposed workers were considered to have chronic bronchitis compared to 10% of controls, with the prevalence being greatest for workers with the highest dust exposure, those employed for more than 10 years, and among current and ex-smokers. Abnormal spirometry results were found in 22% of exposed workers compared with 14% of controls, although most (78%) abnormalities were graded as an ‘alveolar’ or slight deficit. There was no clear relationship between the level of ex posure and spirometry results.

This study shows an increased preval ence of respirat ory symptoms and deficits in spirometry in cement exposed workers in comparison with the control group. A key weakness of this study is the lack of quantitative exposure data. Also, the cement dust exposed group were compared to administrative workers, who may have a different respiratory health status irrespective of the infl uence of cement exposure.

Meo et al. (2002) conducted spirometry in 50 Pakistani cement mill workers. No information on dust exposure levels was available. FVC and FEV 1 were reduced and

FEV 1 /FVC ratio was increased for the cement workers, in comparison with matched

controls.

Pulmonary function was investigated in a group of 50 male workers from a Karachi cement mill (Meo et al. 2002). T he study subjects were volunteers, selected at random. They were descr ibed as apparently healthy, aged 20 - 60 years (mean 36.9), and had been exposed to cement dust for a mean of 13 years. The control group comprised 50 heal thy males, selected from the local Karachi population. They were ma tched with the exposed group for age, height, weight and socio-economic status . Subjects with a range of medical conditions or who smoked or abused drugs were not included in the study.

17Spirometry was conducted in accor dance with ATS guidelines. The highest values from three expirations of the following parameters were recorded: FVC,

FEV 1 , FEV 1 /FCV ratio, PEF and FEF 25-75% and MVV.

Mean FVC and FEV 1 were significantly reduced in the group of cement

workers. For the controls and cement workers FVC (mean ± SE) was 4.03 ±

0.09 and 3.18 ± 0.11 litres and FEV 1 was 3.04 ± 0.08 and 2.54 ± 0.10 litres, respectively. FEV 1 /FCV ratio was significantly increased for the cement workers; the ratios were 75.8 ± 1.4 and 81.5 ± 2.3% in controls and cement workers, respectively. PEF and MVV were significantly lower in the cement workers, but FEF 25-75% was similar to the controls.

The reductions in FVC and FEV 1 accompanied by an increase in FEV 1 /FVC

ratio seen in the cement workers ar e consistent with the presence of a restrictive impairment of l ung function. Overall, this study suggests that longterm exposure to cement dust can caus e an impaired respiratory function, consistent with the previous study. However, a limitati on of this study is that the exposed and control subject selection procedures were not adequately described, so it is not possible to j udge if selection bias was introduced. Another limitation of the study is that there is no information on dust exposure, or a description of the working conditions at the cement m ill so it is not possible to relate the lung function diffe rences to dust exposure levels in a quantitative manner.

Al-Naomi et al. (2001) investigated the respiratory health of 75 cement factory workers in the United Arab Emirates by respiratory questionnaire and spirometry. No information on cement dust exposure levels was available. Among the cement workers there was a higher prevalence of respiratory symptoms and a reduction in spirometry measurements, in comparison with matched controls.

Pulmonary function and the presence of respiratory symptoms were investigated in a group of workers of Pakistani or Bangladeshi origin at a

United Arab Emirates cem ent-producing factory (Al-N aomi et al. 2001). All 75 workers at the factory we re invited to participate. Eight workers did not participate, either because they were on leave at the time of the study, or were senior management personnel. None r eported a history of allergic or chronic respiratory disease prior to jo ining the cement industry. A control group was selected as a group of sim ilar age, nationality and socio-economic status, and with no history of chronic respiratory disease or history of occupational exposure to dust chemicals fumes or gases. They were selected from those seeking a certif icate of good health from a medical clinic so that they could renew their residency permit; the report described them as ‘retail salesmen’. Of the136 unexposed workers in vited to participate, 134 accepted. Information on general and respiratory heath and lifestyle was collected using

an interviewer-administered modi fication of the MRC standardised questionnaire on respiratory symptoms. It was not st ated if the interviewer was blinded to exposure status. Also, information on the use of personal protective equipment was collected. Body mass index (BMI) was calculated from height and weight measurements, and blood pressure was measured. Smoking was analysed as ‘pack-years’ (smoking 20 cigarettes a day for one

18year was defined as a pack-year). Spirometry was conducted according to
ATS recommendations.

The control and exposed groups were similar with respect to age (mean ± SD

44.4 ± 7.5 and 44.2 ± 9.9 year s, respectively, although elsewhere in the report the mean age of the control group is given as 32.1 years), BMI, blood pressure and education. However, t here was a large and statistically significant difference in cigarette cons umption; pack-years were 0.5 ± 0.05 for controls and 4.6 ± 1.1 for the exposed group. The percentage of workers selfreporting the following chronic respirat ory symptoms were higher in the exposed group: cough (10% in contro l vs. 30% in exposed group), phlegm (5% vs. 25%), wheeze (3% vs. 8%), dys pnoea (5 vs. 21%), sinusitis (11% vs. 27%). Asthma was higher in the expos ed group (3% vs. 6% ). Bronchitis, defined by the presence of phlegm/cough fo r at least 3 months of the year, was reported in 4% of controls com pared with 13% of exposed workers. All spirometry parameters were significantly lower in the exposed group. In the control and exposed groups, respective ly, FVC was (mean ± SE) 3.42 ± 0.05 and 3.17 ± 0.08 l, FEV 1 was 2.99 ± 0.04 and 2.59 ±0.07 l/s, and FEV 1 /FVC

ratio was 87.64 ± 0.58 and 81.78 ± 1. 11%. Within the group of exposed workers, spirometry values were lower among supervisors (13 workers), attendants (5) and machine operators (23) who were said to work on the factory floor longer than maintenance workers. The percentages of exposed workers with a mild impairment of FEV 1 (defined as below the lower 95% CI for the predicted value but >60% of predicted) were greater than the controls (43% in controls vs. 67%). Only one s ubject in the study, who was in the exposed group, had a more severe impairment. A comparison of the spirometry results for exposed work ers who were smokers and non-smokers showed few differences, suggesting the sm oking did not have an effect on the spirometry results (alt hough the report text described ‘significantly lower values’ for smokers which were not apparent in the results table). Overall, this study showed a higher prevalence of chronic respiratory symptoms and reduced pulmonary function in cement workers, compared with a group of workers who were not exposed to dusts and chemicals. However, there are inconsistencies in the reporting of t he study, and uncertainties regarding the role of smoking in the differences observed between the cement workers and controls. Consequently the reliance that can be accorded to this study is

limited.

Noor et al. (2000) investigated 62 Malaysian cement factory workers. A respiratory questionnaire was administered and spirometry was conducted. Current dust measurements were available. There was a higher prevalence of respiratory symptoms and a reduction of FVC, FEV 1 and FEV 1 /FVC ratio among the cement workers compared with controls that were university staff or students.

In a briefly reported study, pulmonary f unction and respiratory symptoms were investigated in workers at a Mala ysian Portland cement-producing factory (Noor et al. 2000). Subject selection proc edures were not described. Sixty-two

cement workers were selected for st udy; 32 were non-smokers with a mean age of 35 years and 30 were smokers with mean age of 37. They had worked at the factory for betw een 0.5 and 38 years. Sevent y university students and staff, all not current smokers with mean age of 37, served as controls.

19Airborne dust levels were determined from 2 hour samples taken at six static sampling points in the cement factor y and one at the university. Dust was fractionated into ‘fine’ (diameter < 10 μm) and ’course’ diameter <10 μm particles. Spirometry was conducted acco rding to standard methods. Lifestyle

and medical information were collec ted using an ATS questionnaire.

Dust measurements in the cement fact ory were highest in a packing area, with total dust concentrations of 10.2 mg.m -3 of which 8.0 mg.m -3 were fine particles. In other areas the total dus t concentrations ranged from 3.4 to 0.2

mg.m -3 . FEV 1 and FEV 1 /FVC ratio, unadjusted for height and age, were reduced in both non-smoking and smoking cement wo rkers, in comparison with the control group. These differ ences were more marked when the analysis was limited to subjects aged 30 – 40. For these subgroups, for controls, non-smoking and smoking cement workers, respectively, mean (± SE) FEV 1 was 3.0 ± 0.1, 2.7 ± 0.1 and 2.7 ± 0.2 l and FEV 1 /FVC ratio was

95.5 ± 1.1, 85.4 ± 1.6 and 81.1 ± 3.7%. The differenc es between the controls and both groups of cement workers were statistically significant. The height

distribution within each of these subgroups was similar. Mean FEV 1 when expressed as a percentage of predi cted (using a Malaysian reference population) was reduced in both non-sm oking and smoking cement workers compared with controls; values for the control and two respective control groups were 102 ± 2, 92 ± 4 and 96 ± 4%. The cement worker s were stratified according to whether they worked in areas with high (mean of 8.5 mg.m -3 ), medium (2.8 mg.m -3 ) or low (0.58 mg.m -3 ) dust concentrations and it was found the spirometry parame ters generally had the lowe st mean values in the high exposure group. The prevalence of three respiratory symptoms was significantly higher among cement workers. These were morning cough (in

6% of controls vs. 25% of cement wo rkers), morning phlegm (11% vs. 24%) and chest tightness (6% vs. 19%).

Overall, this study showed a higher prevalence of chronic respiratory symptoms and reduced pulmonary function in cement workers, compared with university students/staff. One weakness of the design of this study is that theexposed and control groups were unlikely to be equivalent in terms of socioeconomic status, a possible confoundi ng factor. Nevertheless, among the cement workers the effects on pulmonary function were most marked for those with the highest dust exposures, s uggesting that cement exposure can affect respiratory health.

Mengesha et al. (1998) administered a respiratory questionnaire and conduced spirometry and peak flow measurements in 53 Ethiopian cement factory workers. Current dust measurements were available. There was a higher prevalence of respiratory symptoms among cement workers, compared with controls. FVC, FEV 1 and

FEV 1 /FVC ratio were lower for the group with the highest dust exposures.

Pulmonary function and the presence of respiratory symptoms were investigated in persons working in dusty environments in Ethiopia (Mengesha et al. 1998). Among those investigated we re 53 cement factory workers, all non-smokers, chosen at random. No information on their age, gender or duration of employment was reported. The contro l group was 111 males and 100 females, all non-smokers who worked in areas free of dusts. They were

20said to live in the same area and to be of the same socio-economic status as the exposed workers. The method of recr uiting the controls was not stated. Information on respiratory symptoms wa s gathered using a modification of the MRC and ATS questionnaires and used to identify respiratory conditions referred to as chronic cough, chroni c bronchitis and bronchial asthma. Spirometry was conduct ed using standard methods for 71 controls and 28 cement workers prior to commenci ng a work shift. PEFR was determined using a Wright peak flow meter. Current respirable airborne dust concentrations were determined from per sonal air samples. A total of 11 samples, taken over 6 - 8 hour periods, were analysed.

The mean dust level (± SD, presumably a 4 - 6 h TWA) for rotary kiln workers was 3.2 ± 3.5 mg.m -3 and for packing workers 43.1 ± 35.3 mg.m -3 . The prevalence of respiratory conditions was significantly higher among the cement workers; the pe rcentage of workers in the control and exposed groups, respectively, was 9% and 30% with chronic cough, 9 and 26% with

chronic bronchitis and 8% and 32% with bronchial asthma. The spirometry

results for the controls and cement dus t workers were not presented in a way that allowed a comparison. However, it was possible to compare the results for 12 operators of the rotary kiln with those for 16 cement packers. Mean FVC was similar, FEV 1 was slightly lower for the packers (91% vs. 98% of predicted) and FEV 1 /FVC was significantly lowe r for the packers (90% vs. 98%). PEFR was lower for the packers, but the difference was not statistically significant (92% vs. 98% of predicted) . Study shows increased prevalence of respiratory symptoms in cement workers, compared with the unexposed controls, and poorer lung function test re sults in the cement workers with the highest current dust exposure.

Abuhaise et al. (1997) investigated the respiratory health of 348 Jordanian cement factory workers, who were divided into three groups exposure groups, based on current dust exposure measurements. A respiratory questionnaire was administered and spirometry was conducted. There was a higher prevalence of asthma in the group with the highest dust exposure, but the spirometry results were similar for all three

groups.

Pulmonary function and respiratory symptom s were investigated in workers at a Jordanian Portland cement-producing factory (Abuhaise et al. 1997). All workers employed at the factory for more than 3 years were invited toparticipate; 442 (73%) agreed. After exclusions due to family or preemployment history of respiratory di sease, being an ex-smoker (only smokers and non-smokers were included), participation in other activities involving dust exposure, unacceptable spirometry per formance, 348 workers were available for study. They were predominantly middle-aged men, wit h a mean age of 41 years and most had worked at the plant for between 3 and 14 years. There was no unexposed control group. Demogr aphic information and occupational

and medical histories were collected us ing a modification of the MRC and ATS questionnaire on respir atory symptoms. Spirom etry was conducted once during a workshift using procedures t hat were in accordance with ATS recommendations. Observed readings were reported as percentage of predicted. Current respirable dust ex posure levels were measured by personal sampling. Between 3 and 5 workers in each of 4 plant areas were

21sampled. Three exposure groups were identified; group 1, the lowest exposure group, included administr ative and transport workers; group 2 included maintenance staff, clinker wo rkers and foremen; group 3 included packers and cement mill workers.

The measured geometric mean (± SE) respirable dust concentrations (presumably 8 h TWAs) were 0.5 (±2. 1), 1.6 (±2.6) and 3.9 (±4.0) mg.m -3 in exposure groups 1, 2 and 3, respectively . Overall, 58% of workers reported no respiratory symptoms duri ng the last 3 years. The most frequent symptoms were cough reported by 19% and d yspnoea by 18%. About 16% were

considered to have asthma and about 15% were considered to have chronic bronchitis (defined as phlegm/cough for at least 3 months each year for at least 2 years). The prevalence of asthma was higher in group 3 (27%), but for other respiratory symptoms and condi tions there were no meaningful differences between the groups. Age or duration of employment had no influence on questionnaire responses. The prevalence of respiratory symptoms was higher am ong smokers. Mean FEV 1 , FVC, FEF 25-75% and

FEV 1 /FVC ratio were similar for all thr ee exposure groups. Overall, this study did not provided any convincing evidence that the exposure conditions at this factory were causing respiratory probl ems in the workforce. Because there were considerable overlaps in the dus t exposure concentration ranges for the three study groups the power of the study to detect a dose-response relationship would be low. The participati on rate of 73% raises the possibility that the study population was not r epresentative of the workforce.

Chanrawanshi and Pati (1996): this study does not contribute any useful information

on the effects of cement dust.

PEFR was measured in Indian cement-pr oducing factory workers, with the primary aim of assessing the effects of shift work on pulmonary function (Chanrawanshi and Pati 1996). The results showed poorer lung function in shift workers, but no exposure data was provided and no conclusions regarding cement can be drawn.

Yang et al. (1996) administered a respiratory questionnaire and conducted spirometry on 412 Taiwanese cement factory workers. They were exposed to mean respirable dust levels of about 4 mg.m -3 . The prevalence of respiratory symptoms was higher and FVC

and FEV 1 were reduced, in compar ison with controls.

In Taiwan, pulmonary function and respiratory symptoms were investigated in

workers at four cement factories (Yang et al. 1996). The study considered all male workers who had been employed for mo re than 5 years at one of these

factories. After a small num ber of exclusions because of refusal to participate or unacceptable spirometry performanc e, 412 production workers were investigated. Their mean age was 44 years and their mean duration of employment was 17 years. A group of 179 administrative workers at these plants served as controls. Their ages, duration of employment and prevalence

of smokers was similar to the exposed group. Demographic information and employment histories were obtained by interview. Information on respiratory symptoms was obtained us ing a modification of the ATS questionnaire. Chronic bronchitis was defined as cough/ phlegm on most days for at least 3

22months of the year. Spirometry was conducted according to ATS

recommendations. It was not stated if the interviewer and spirometry technicians were blinded to exposure st atus. Current respir able dust exposure levels were measured from personal air samples, for persons working in all the principal job categories. A total of 198 samples, taken over 4 - 8 hour periods, were analysed.

Geometric mean (± SD) respirable dust c oncentration for control subjects was

0.41 ± 0.98 mg.m -3 and for the exposed group, 3.58 ± 4.89 (range 1.28-8.12)

mg.m -3 . The prevalence of cough (19 vs. 12%) and phlegm (18 vs. 13%) was significantly higher in the exposed group. However, the prevalence of wheezing, dyspnoea and chronic bronchiti s was similar in the two groups. After adjustment for smoking, age and heigh t, FVC (3.80 l for controls vs. 3.54 l for exposed), FEV 1 (2.98 vs. 2.73 l) and FEV 1 /FVC (78.42 vs. 77.12%) were significantly reduced in the exposed gr oup, in comparison with the controls.

There were similar reductions in FEF 50 , and FEF 75 . The study showed an increase prevalence of respiratory symptoms and reduced pulmonary function in workers exposed to cement dust. A pot ential weakness of this study is that there may have been socio-economic differences between the cement exposed workers and administrative contro ls, which could have contributed to the observed differences between the groups.

Yang et al. (1993) administered a respiratory questionnaire and conducted spirometry on 661 Taiwanese cement factory workers. Current dust measurements were available. The prevalence of cough was greater in the group with the highest current respirable dust exposure of 1.24 mg.m -3

.

The respiratory health of cement work ers at the four pl ants in Taiwan was investigated (Yang et al. 1993). It is po ssible that some of the respiratory and exposure data reported in this publicat ion was also used in the Yang et al. (1996) report, summarised above. This earlier report provides information on respiratory symptoms and sp irometry for 661 cement factory workers. The

workers were classified into thr ee groups according to respirable dust exposure concentration. Group 1 were 146 administrative workers, with mean dust exposures of 0.22 (range 0.03-1.4) mg.m -3 . Group 2 were 140 maintenance workers, machine operat ors and drivers, with mean dust exposure of 0.55 (0.13-1.94) mg.m -3 . Group 3 were 375 workers in jobs with the highest exposures, for example packi ng or preparing raw materials; mean dust concentration was 1.24 (0.38-8.12) mg.m -3 . The mean age and duration of employment of the th ree groups were similar, although the percentage of smokers was higher in groups 2 and 3. Current respirable dust exposure levels were determined by personal breathing zone sampling over 4 to 8 hour periods. Between 48 and 78 samples were taken for each exposure group.

The only indication of a difference in respiratory health between the groups was the prevalence of cough, which wa s higher for group 3 (17% compared with 11% for groups 1 and 2); this differenc e was statistically significant after adjusting for smoking. The prevalence of other symptoms, chronic bronchitis and spirometry results were similar for all groups. Overall, this study showed an increased prevalence of one respirat ory symptom (cough) in workers with current respirable dust exposure of 1.24 mg.m -3

.

233.4.1.3 Study using chest radiography

Abrons et al. (1998) conducted chest radiography in 2640 US cement factory workers. Information on current dust exposure levels was available. A slight increase in the prevalence of minor pulmonary radiographic abnormalities, which seems to be confined to current smokers, was observed for the cement workers in comparison with blue collar controls. Very few of the cement workers had radiographic findings that

were indicative of si gnificant pulmonary disease.

In a cross sectional study, chest radi ography was conducted in 2640 randomly
selected workers from 16 US Portland ce ment producing fact ories (Abrons et al. 1997). This is a report of an additiona l investigation conducted on the same subjects as a study reported in 1988, which showed no convincing evidence of a relationship between cement dust exposure and the presence of respiratory symptoms or and changes in pulmonary function (Abrons et al 1988, cited in HSE 1994). These factorie s, were a random sample of the 153
US cement factories. All workers were invited to participate, and 87% agreed. The mean age of the exposed group was 41 years, and 95% were male. The control group comprised of 1458 blue-collar workers drawn from the food, textile and electrical equipment manufacturing indu stries, judged on the basis of workplace inspections by a hygienist not to have been exposed to known respiratory hazards. Only 55% of the unexposed worker s invited to participate agreed. There were age and gender differences in comparison to the exposed group; for controls, the mean age wa s 34 years, and 50% were male. Standard posterio-anterior chest radiograph s were assessed according to the 1971 ILO-U/C system, by three independen t, qualified, readers. Demographic information and medical and employment histories (including information on asbestos exposure) were obtained by an interviewer-administered questionnaire. Current dust exposure leve ls were determined by personal fullshift sampling.

The overall geometric mean levels of resp irable (211 samples) and total dust (1011 samples) were 0.57 mg.m -3 (range 0.01-46.22) and 2.90 mg.m -3 (range 0.01-78.61) (presumably an 8 h TWA), respectively. Crystalline silica was detected in about 15% of personal respirable dust samples, and levels in

about 10% of these exc eeded a limit of 0.05 mg.m 3 . Additionally, no asbestos fibres were found in any area air samples taken, or in bulk material samples. Radiography revealed low prevalenc e of abnormalities for both exposed and

control workers. Rates for both rounded and irregular small opacities (category 1 profusion or greater) were about 1% among cement workers compared with about 0.1% for the cont rol group. Three cement workers had rounded small opacities of category 2; all other cases of opacity were category 1. The prevalence of pleur al abnormalities was about 1.6% in exposed workers and 0.2% in controls. These differences were statistically significant, and remained so after adj ustment for age and smoking. The prevalence of abnormalities for the subset with limited previous exposure to other agents was similar to that of t he whole group of cement workers. A comparison of the findings for this s ubset with controls by smoking status indicated that that the significant differences were confined to current

24smokers. An analysis that took account of duration of employment in current and previous current j ob and cement exposure levels based on current measurements indicated a positive relationship between exposure and with pleural abnormalities, but not with opacities.

This study indicates an association between employment in the cement industry and a slight increase in t he prevalence of minor pulmonary radiographic abnormalities, which seems to be confined to current smokers. It is noted that very few of the cement workers had radiographic findings that were indicative of significant pulmonar y disease. Because current exposure levels covered such a wide range, and historical exposure data were not available, no information on dose-response relationships can be gained from this study.

Laraqui et al. (2001) found a higher prevalence of respiratory symptoms together with spirometry deficits among Moroccan concrete manufacturing workers, compared with

controls.

Laraqui et al. (2001) investigated the pr evalence of respiratory problems in workers at two ready-made concrete pr oduction plants in Morocco. This study is considered briefly, as the workers would have been exposed to gravel and sand (and hence silica) as well as to cement dust. The study population was 120 concrete workers, who were co mpared with 120 civil servants. No quantitative airborne dusts measurem ents were available. A higher prevalence of respiratory symptoms, rh initis, conjunctivitis and dermatitis was reported among the concrete workers. Also, the proportion of workers with spirometry deficits, as defined by an official French government grading system, was higher among the c oncrete workers.

3.4.1.4 Studies invest igating symptoms only

Alvear-Galindo et al (1999) administered a respiratory questionnaire to 425 Mexican cement factory workers. A semi-quantitative dust exposure assessment was conducted. The prevalence of respiratory symptoms was highest among those with the highest exposures.

The association between levels of expos ure to cement dust and respiratory symptoms was studied in workers at a Mexican Portland cement-producing factory (Alvear-Galindo et al. 1999). T he study population was 425 workers at a factory, representing 95% of the wo rkforce. Their mean age was 39 years. All had worked at the factory for their ent ire working life. Six semi-quantitative levels of dust exposure were established from interviews with a small group of experienced workers, taking account of time spent at vari ous work positions and the visibility in those areas. Each le vel was given a score of 1 (the lowest) to 6. A list of 85 work positions we re drawn up and exposure scores were assigned to each position. Informati on on the work history was obtained by questionnaire, and a cumulative exposur e score was calculated for each worker. It was stated that exposure to other respiratory tract ir ritants, including tobacco smoke, was minimal. Info rmation on respiratory symptoms was gathered using the ATS questionnaire. Also, information on respiratory illness history was available in personnel reco rds. An occupational health physician

25considered the informati on from these two sources to make an assessment of the presence of respiratory disease. Some workers were said to have received compensation for occupational diseases.

Most workers had been exposed to levels of 4, 5 or 6 for most of their working life. Very few workers under the age of 25 reported respiratory symptoms. However, 8% of workers aged 25-44 years and 16% aged 45 or more were diagnosed with bronchitis; 72% and 83% , respectively, had dyspnoea and 24% and 32% had wheezing. A diagnosis of ‘occupational respiratory disease’ (the diagnostic criteria were not described) was made for 32% and 52% of workers from the two respective age groups. The prevalence of respiratory problems was greatest among those wit h the highest cumulative exposure scores, after adjusting for age.

This study reported a high prevalence of respiratory problems at the cement factory, which was positively associat ed with the estimated cumulative dust exposure. A limitation to the value of th is study is that quantitative exposure

information was not available.

Abou-Taleb et al. (1993) administered a respiratory questionnaire to 304 cement factory workers in the United Arab Emirates. Chronic bronchitis was present in 12% of workers, but there was no control group for comparison.

The respiratory health of a sample of United Arab Emirates cement workers was assessed (Abou-Taleb et al. 1995). From four cement productions factories, 304 workers were selected at random. Thes e represented about
50% of the workers from each fact ory. Their mean age was 38 years, and 88% were of Indian nationality. Dem ographic and lifestyle information and medical histories were obtained by in terviewer-administered questionnaire. Respiratory health problems most frequent ly reported were chronic cough in 19% of workers and chronic bronchitis (dia gnostic criteria were not stated) in 12%. Other health problems reported in a minority of workers included sneezing with runny or stuffy nose, burning eyes, dermatitis, headache and fatigue. Is not possible to draw firm conclusi ons from this study as it is difficult

to assess the contribution of cement dust to the reported health problems in

the absence of either an unexposed group or groups with contrasting dust exposure levels for comparisons.

3.4.1.5 Summary of information on the effects of long-term exposure on nonmalignant respiratory disease

HSE (1994) noted evidence that repeated exposure to Portland cement has produced chronic bronchitis and impai red pulmonary function, but firm

conclusions could not be drawn because of limitations in the available data. The effects of long-term exposure rema in poorly studied, particularly because there are no longitudinal prospective studies.

Of the 15 recent studies available, mo st were cross sectional in design, conducted in Portland cement produc tion plants outside of Europe. The exception was a retrospective cohort study of a relatively small number of

26Norwegian cement plant workers (Fell et al. 2003). This study provided evidence that long-term exposure to an average of respirable dust concentration of about 1 mg.m -3 is not associated with deficits in lung function
or with an excess of COPD. Of the re maining studies, all had significant design limitations. Notably, due to the cross sectional design the adverse effects of cement may be underestimat ed because this type of study cannot take account of workers that may have left the industry due to work-related health problems. Another key weakness of theses studies is that a number lacked quantitative exposur e data and none included hist orical exposure data. Nevertheless, many of these studies provide a consistent picture of the presence of respiratory symptoms, r eports of bronchitis, and pulmonary function deficits in workers exposed to cement plant dust. Typical symptoms associated with cement plant work were cough, phlegm and dyspnoea. Deficits of lung function were usually seen as a reduction in FEV 1 , FVC and

FEV 1 /FVC ratio, suggesting an obstructive impairment. In studies that provided some information on dust expos ure conditions, the lowest current dust exposure concentrations associated with poorer lung function were about 3 mg.m -3 total dust (Mwaiselage et al 2004), or about 2 - 4 mg.m -3 respirable dust (Noor et al. 2000, Yang et al 1996). The lowest concentration associated with in increase in respiratory symptoms was 1.2 mg.m -3

. However, no reliable conclusions about dose-response relationships can be drawn because of the

limitations of these studies . Nevertheless, the evidence provided by the recent studies qualitatively str engthens the picture presented in the earlier HSE (1994) review.

Overall, the pattern of evidence clearly indicates that occupational exposure to cement dust has produced deficits in respiratory function. However, the evidence available at the present time is insufficient to establish with any confidence the dose-response rela tionship for these effects.

273.4.2 Mortality and cancer studi es involving workers with long-term exposure to cement dust

HSE (1994) concluded that mortality studies conducted on cement workers provided no evidence of increased in cidence of death from non-malignant respiratory disease. With regard to cancer, three cohort mortality studies conducted in cement manufacturing workers found elevated SMRs for

stomach cancer. The elevation was st atistically significant in one study conducted in the UK (SMR 1.75, based on 22 observed deaths,). In other two
studies the SMRs were not statistica lly significant (SMR 1.19 based on 24
deaths and SMR 1.35 based on 27 deaths ). Several other studies found associations between exposure to cem ent and various site-specific cancers but these were isolated reports a nd no firm conclusions could be drawn. Overall, HSE (1994) came to the view that there was no convincing evidence for an increased incidence of any site-s pecific cancer resulting from exposure to cement dust, but it was also acknow ledged that the resu lts emerging from the studies available up to 1991 were not consistently and reassuringly negative.

Since 1991, a number of mortality and cancer cohort studies conducted in cement production workers of cement masons have been conducted. Also, a

series of case control studies conduc ted in Germany have drawn attention to occupational contact with cement as a po ssible risk factor for cancers of the oral cavity, pharynx and larynx. The pr esent review also briefly considers earlier case control studies that have investigated risk factors for laryngeal cancers, and other recent cancer relat ed studies that include subjects that may have been exposed to cement.

3.4.2.1 Mortality and canc er cohort studies in ce ment production workers or

masons

Recent cohort studies conducted in cement production workers in three northern European locations, in Sw eden, Denmark and Lithuania, are available. Additionally, a cancer cohort study has been conducted in Icelandic cement masons. These studies are appraised below, and summarised in

Table 2.

Jakobsson et al. (1993) investigated mortality and cancer morbidity in about 2400 Swedish cement factory workers. Overall mortality and cause-specific non-malignant mortality for the cement workers were similar to the national rates. However, the analysis of individual tumour sites revealed an increased risk of tumours of the right side of the colon (SIR 2.7, 95% CI 1.4 - 4.8, 12 cases). The risk was increased among those with more than 25 years cement plant work.

In a retrospective cohort study mortalit y and cancer morbidity experiences of a group of about 2400 workers at two Sw edish cement production factories were investigated (Jakobsson et al. 1993). This study was conducted as a follow up to the Jakobsson et al. (1990) case control study summarised by HSE (1994), which reported an increased ri sk of colorectal cancer associated with one of the cement factories (factory A). The cohort consisted of all men employed at the factories at the start of January 1952 or since then, and with

28a total employment of at least one year. Mortality and cancer morbidity
information to the end of 1986 was obt ained from death ce rtificates and a national tumour registry and compared with the age-adjust ed rates for the general population of Sweden (mortality) or the r egions in which the plants were located (morbidity). About 90% of the cancers diagnoses were confirmed by histology or cytology. The analysis focused on cancers occurring 15 years or more after commencement of exposure.

Very limited exposure data were available. The report states that new cement ovens and automatic process controls were introduced at both plants during the 1960s and ventilation was improved dur ing the 1970s suggesting that dust exposure during the latter years of t he study period were considerable lower than earlier. At factory A, total dust measurements made from the mid-1970s onwards were generally lower than 10 mg.m -3 (presumably as a TWA). Dust surveys conducted in factory B during the early 1970s showed that total dust

airborne concentrations were generally less that 20 mg.m -3 and in later years less that 10 mg.m -3 . Concentrations greater than 100 mg.m -3 were found for some cleaning and maintenance tasks, although it was suggested that respiratory protection might have been us ed during these oper ations. Factory B measurements were based on personal sampling and expressed as a TWA, although the sampling time was not stated. The quartz content of the dust was said to be generally less than 5%, and no cases of silicosis have been reported at these plants.

Overall mortality (495 obser ved deaths vs. 527 expe cted) and cause-specific non-malignant mortality for the cement workers were similar to the national rates. Also, overall tumour morbidit y (162 observed cases vs. 160 expected) did not differ from the regional rates. However, the analysis of individual tumour sites revealed a significant incr eased risk of tumours of the right side of the colon (SIR 2.7, 95% CI 1.4 - 4.83, 12 cases). The risk was increased among those with more than 25 years cement plant work (SIR 4.3, 95% CI 1.7

- 8.9, 7 cases). However, the risk of right-sided colon cancer was not significantly increased at factory A, which was a ssociated with an excess of colorectal cancer morbidity in the Ja kobsson et al report of 1990. All colon cancer cases had been confirmed by histology or cytology. There was no

excess of tumours at other sites

. The authors discussed the possibility of bias due to the use of an inappropriate refer ence population. Farmers are known to have very low rates of colon cancer and a relatively high proportion of farmers in the localities of the cement plants may have resulted in a bias of the magnitude of the calculated SIR in t he direction of an overestimate.

As an extension to their 1993 study, Jakobsson et al. (1994) reanalysed mortality and cancer morbidity for the 1520 Swedish cement factory workers. Comparisons with other groups of blue-collar workers and with the general population were conducted. An increased risk of cancer of the right side of the colon (SIR 2.6, 95% CI 1.4 - 4.6) for

the cement workers was confirmed.

In a later report, the risk of right-s ided colon cancer at the two Swedish cement factories was compared with that for asbestos cement workers, other industrial workers without significant ex posure to mineral dust or fibres and fishermen in Sweden (Jakobsson et al. 1994). All members of the

29occupational groups had a minimum employment of one year, and only cancer morbidity occurring more than 15 years after the commencement of employment was considered. Cancer mortality and morbidity for the period 1958 to about 1987 (slightly later for fi shermen) was ascertained and SMRs
and SIRs were calculated with referenc e to the general male population of
Sweden. The cohort of cement worker s consisted of 1526 blue-collar workers with a median birth year of 1927. The asbestos ce ment cohort was 981 bluecollar workers from a building material s factory, with median birth year 1913.

The ‘other’ industrial workers cohort consisted of 3965 blue-collar workers from a variety of industries where some chemical exposures were likely. The cohort of fishermen was 8092 in number, with a median birth year of 1924.

Overall cancer mortality for the cem ent workers was similar to the general population (SMR 1.02, 95% CI 0.92-1.25), and to ‘ot her’ industrial workers. The cancer mortality for the asbestos workers was slightly higher, and for the fishermen slightly lower. Morbidit y from right-sided colon cancer was increased among cement workers (SIR 2. 61, 95% CI 1.35-4.57), but risk of

left-sided colon cancer was not increas ed. The findings for asbestos cement workers were similar. Morbidity for co lon cancers among the ‘other’ industrial

workers and fishermen was similar to the general population. This study showed an increased risk of right-si ded colon cancer among workers with long-term exposure to cement dust compar ed to other blue-collar workers, which constitute an appropriate refe rence population, and to the general population.

Vesbo et al. (1991) investigated cancer morbidity in 546 Danish cement factory workers. No evidence of an increased risk of cancer was reported, when compared with a control group drawn from the local population.

The relationship between employment at a Danish Portland cement factory and cancer morbidity was investigated in a cohort study (Vesbo et al. 1991). The cohort of cement workers compris ed of all men aged 46- 69 living in the city of Aalborg who had worked at the factory for at least one year prior to 1974; there were 546 men meeting these criteria. The control group was all men of the same age group living in th is city who had not worked at the factory for a year or more and who were born on the 1st or 15th of each month; they numbered 856. Information on employment and lifestyle factors was gathered by questionnaire. From fact ory personnel records, the cement workers were classified as having either 1-20 years or ≥ 20 years employment. Information on actual o ccupation within the factory was not available so it was not possible to ca tegorise individuals into more precisely defined exposure groups. The control subj ects were categorised into three occupational groups, blue-collar workers, white-collar workers and ‘others’.

Information on cancer cases for t he period 1974 to 1985 was obtained from the Danish Cancer Registry. The number s of observed cases of cancer for each study group were compared to the expected number based on cancer incidence rates for the relevant age gr oups for the total male population of

Denmark.

Airborne cement dust meas urements were not made prior to 1974. Personal sampling during 1974 showed that 9% of respirable dust measurements were

30greater than 5 mg.m -3 . No increased risk of all types of cancer was seen among cement workers compared with eith er the general male population or with each of the control groups. However, the risk of respiratory cancer was higher among cement wo rkers when compared to the general male population. The authors provided a more detailed comparison of the risk of respiratory cancer for cement work ers and white-collar controls, after excluding all men with asbestos exposur e due to employm ent at a nearby asbestos-cement plant (approximately 5% of cement workers) and controlling for age and smoking. The RRs for respirat ory cancer were 0.5 (95% CI 0.1- 1.5) for men with 1-20 years cement fa ctory employment and 1.0 (95% CI 0.4- 2.6) for men with ≥ 20 years employment. The aut hors pointed out a drawback with respect to comparisons with the bl ue-collar control group, since members of this group may have been exposed to asbestos at a large local shipyard. Overall, this study provides no conv incing evidence of an increased risk of cancer morbidity associated with cement dust exposure at the cement factory.

Smailyte et al. (2004) investigated morta lity and cancer morbidity in 2500 Lithuanian cement factory workers. There was an increased incidence of lung cancer among cement workers (SIR 1.5, 95% CI 1.1-2.1) compared to the general population, but smoking was not taken account of in the analysis. A dose-related trend towards an increased incidence of stomach cancer was observed, although the number of cases

was small.

In a cohort study, mortality and canc er incidence among workers at a

Lithuanian Portland cement producing plant was investigated (Smailyte et al 2004). The study population comprised a ll workers employed by the cement producing departments for at leas t 12 months between 1956 and 2000 and who were available for the follow-up period of 1978 to 2000. The study population numbered 2498, which was about 94% of all those who had worked at the plant from 1978 to 2000. This cohort represented 43490 person years of exposure. Approximately 70% of the study population were men. Subjects were identified fr om factory records, whic h provided information on age, employment start and finish dat es, and factory departments in which each subject worked. Information on vita l status, cause of death and cancer cases were obtained from Government popul ation registers, death certificates
and the Lithuanian Cancer R egistry. SIRs and SMRs were calculated with reference to the gender and age-adjust ed rates for the general Lithuanian population.

Some dust exposure info rmation was available from 1975, expressed as

annual mean total dust concentrations. T hese were calculated from static sampling measurements (sampling time was not stated) conducted four times a year in various departments. Annual mean dust concentrations were highest in the packing (ranging from 19.1 to 15.0 mg.m -3 ) and calcining (19.2 to 8.2

mg.m -3 ) departments.

The overall mortality among male ce ment workers was not increased (376 observed deaths, SMR 1.0, 95% CI 0.9-1.1), but deaths from malignant neoplasms were increased (102 observed, SMR 1.3, 95% CI 1.0-1.5), mainly due to lung cancer mortality (SMR 1.4, 95% CI 1.0-1.9). There was no excess mortality for non-malignant respirator y disease. Among females, overall

31mortality and mortality for specific caus es was similar to that of the general Lithuanian population. The cancer incidence data for male cement workers revealed a slight excess for all malignanc ies (SIR 1.2, 95% CI 1.0-1.4). The only site showing a significant excess wa s the lung (SIR 1.5, 95% CI 1.1-2.1).

A total of 389 cement workers had been also been involved with the production of asbestos cement at another plant in the same area. When these were excluded from the analysis the incidence of lung cancer remained elevated (SIR 1.4, 95% CI 1.0-2.0). There was a slight trend towards an increased incidence of lung cancer with increasing time since first employment and duration of employment. The authors presented cancer SIRs for categories of cumulative dust exposure, but it was not clear from the report how this index of exposure was calcul ated. There was no obv ious relationship between lung cancer and cumulative exposure, although the SIRs were significantly increased for the two highest dust exposure categories designated ‘55-130 mg.m -3 year’ (SIR 2.0, 95% CI 1.2-3.4) and ‘>130 mg.m -3
year’ (SIR 1.8, 95% CI 1.1-3. 0). The authors of the study drew attention to an

increase in the incidence of cancers of the urinary bladder , but the increase was not statistically significant (8 case s, SIR 1.8, 95% CI 0.9-3.5) and there was no convincing relationship with dur ation of employment of cumulative dust exposure. There was a trend toward s an increased incidence of stomach cancers with cumulative dust exposure; for a ‘55-130 mg.m -3 year’ exposure group the SIR was 1.1 (4 cases, 95% CI 0.4-2.8) and for a ‘>130 mg.m -3 year’ exposure group the SIR was 1.5 (6 cases, 95% CI 0.6-3.0).

The authors discussed a major limitation of this study, which is that no data on tobacco consumption was available. It was stated that about half of the male population of Lithuania are smokers, and it is likely that more blue-collar

workers smoke than white-collar workers. Therefore it is possible that the results of this study may have been subjected to a confounding influence of smoking. If the analysis had taken account of smoking, the statistically significant differences observed for the SIRs for lung cancers in this study may have been eliminated. For this r eason it is not possible to draw

conclusions about the role of cement dus t in reported increase in the risk of

cancers. It is noted that due to the crude nature of exposur e assessment there is a high potential for exposure group miscl assification, which could result in the masking of any dose response relationships.

Rafnsson et al. (1997) investigated cancer in 1172 Icelandic cement masons. The study revealed an increased risk of lung cancer among the masons in comparison with the general population of Iceland (SIR 1.7, 95% CI 1.1-2.5). The SIR was increased when the analysis allowed for a latency period of 30 years from the start of work as a mason.

Rafnsson et al. (1997) conducted a retros pective cohort cancer study in all
1172 Icelandic licensed masons who were born after 1880 and alive in 1955. The cancer experiences from 1955 to 1993, or until death if before 1993, were

ascertained from the nati onal Cancer Registry. It was possible to obtain information on the status of all study s ubjects. Most of the cancer cases had been verified by histological diagnosis. Mas ons alive at the time of the study were questioned on their smoking habits and the number of years worked as

a mason. The main task of the masons was to finish and smooth the surfaces of concrete structures using wet concre te, applied by trowel or by spraying.

32No quantitative exposure data were ava ilable, although it was stated that when spaying inside a thick mist of an aerosol of concrete was produced that

made it difficult to see across the room . Dermal contact with the wet concrete

was described as ‘intensive’ on hands and face. The concrete contained cement, sand, water and other com pounds. A survey showed that about 88% of responding masons had worked as finishers for at least 10 years.

The study showed an increased risk of lung cancer in comparison with the general population of Icel and (SIR 1.69, 95% CI 1.09-2.49). The SIR was increased when the analysis allowed for a latency period of 30 years since completing vocational training (SIR 1. 77, 95% CI 1.01-2. 88). The percentage of never-smokers among the masons was estimated to be lower than in the general population, but this could not account for the increased risk. For all

other tumour sites there were no incr eased risks for the cement masons. The masons would have been exposed to silica, but there were no identified cases of silicosis. Strengths of the study are that the design provided protection against subject selection bias, canc er ascertainment was reliable and complete, and the follow-up period was long. However, weaknesses of the study are that exposure information was not available and an analysis of

cancers in relation to duration of employment was not conducted.

333.4.2.2 German case control studies for cancers of the oral cavity, pharynx and larynx

Maier et al. conducted a series of population-based case control studies in cancer patients from the Gliessen and Heidelberg University Ear Nose and Throat (ENT) clinics investigating occupational and other risk factors for

cancers of these sites. These studies are appraised below, and summarised

in Table 3.

Maier et al. (1991) investigated the occupational risk factors for cancers of the oral cavity, pharynx and larynx in 200 cases and 800 controls. The study reported an

elevated risk of cancer associated with occupational exposure to cement. The estimated RR was 2.4 (95% CI not stated) after adjustment for smoking and alcohol consumption.

In the first study the occupational ex posure histories of cases of squamous cell carcinomas of the oral cavity , oropharynx, hypopharynx and larynx were investigated (Maier et al. 1991). The in vestigations were conducted at the Gliessen University ENT Clinic and the Heidelberg University ENT clinic. The same patients were investigated in an earlier study, in which non-occupational

risk factors for cancers at these sites were analysed (Maier et al 1990). The first 100 patients with the above diagnosis attending each clinic for consultation or treatment from Sept ember to December 1987 (Gliessen) or February 1988 to April 1988 (Heidelberg) were selected for each study. Patients who were first diagnosed more than three years prior to the study period were excluded. The Gliessen c ontrol group consisted of 400 male patients attending either the ENT (200 patients) or Medical (200 patients) Clinics of Gliessen University who had no known cancer. Four controls were assigned to each case, two from each of the ENT and M edical Clinics, who were matched for age (± 2 years) and size of their home. The selection or number of Heidelberg cont rols was not described in detail, although the design of this part of the study was said to be similar to that of the Gliessen study. Approximately 30% of Gliessen case and control patients and 20% of Heidelberg case and control patients who were invited to participate in the study declined.

Occupational exposure information for each of the Gliessen patients was obtained by one interviewer using a computerised questionnaire that focussed mainly on exposures to harmful subst ances at work. Patients were asked simply whether or not they had been exposed to asbestos, welding gases, organic compounds, heavy metals, coal products, wood dust, cement, herbicides and ionising radiation. No information on duration or frequency of exposure was collected. Details of the method of collecting exposure information for the Heidelberg patients wa s not described in detail, except it
was mentioned that information of durati on of exposure was collected and the analysis included only substances to which the patient had been in contact

with for at least once a week for more than 10 years. It was not stated if the
interviewer was blinded to case/control st atus, or if the pati ents were aware of the purpose of the investigation. The anal ysis of the result s of the Heidelberg study included an adjustment for the influence of alcohol consumption and smoking. RRs for occupational risk factor s were estimated from odds ratios.

34The majority of cases were within t he age range 49 to 66. The distribution of

tumour sites was similar for both st udy centres; approximately 45% were carcinomas of the larynx, 23% of the oral cavity, 24% of the oro-pharynx and 8% of the hypo-pharynx.

The exposure information for the Gliess en and Heidelberg study centres was analysed separately. For the Gliessen study, the percentage of cases with cement exposure was significantly higher than controls (14.5% of controls vs. 25% of cases). The percentage of ca ses with asbestos exposure was also significantly higher than controls (22% vs. 40%). There were no differences

between the cases and controls for the other exposures. For the Heidelberg study, the proportion of cases with occupational exposure to cement (estimated RR 4.4, 95% CI 2.4-8.4), organic compound s, wood dust or coal products were significantly greater t han controls. After adjustment for the effects of alcohol and tobacco only t he estimated risks for cement remained statistically significant (RR 2.4, 95% CI not stated). The RRs for cement

increased with duration of exposure; compared with that for less than 5 years exposure, the estimated RR was almo st 3 times higher for 5-20 years exposure, 5.5 times higher for 20-40 year s, and 6.3 times higher for more than 40 years. However, the confidence inte rvals of the estimated RRs for these subgroups were not reported, neither were the number of cases within each exposure band, so it so it is not possible to assess the robustness of this

trend.

A limitation of the Gliess en study is that the expo sure assessment identified anyone who had come into contact with a particular substance at any time during their work; the authors consider th is part to be a pilot exercise for the Heidelberg study. The Heidel berg study provides evi dence of an association between cement exposure and cancer of the upper respiratory/digestive tract. As with many case control studies, the exposure assessment relied on the recall of the subjects, which may be subject to bias because the cases may have a greater motivation to recall c hemical exposures than the control patients. Such a bias would result in an overestimation of risks associated with cement exposure. Similarly there may have been interviewer bias in that the interviewer may have pressed harder to gain information on occupation exposure for the cases. However, there is no logical reason for the cases to be more strongly motivated to recall cement exposure in preference to exposures to other substances, unless t hey were aware of a hypothesis that cement exposure was associat ed with cancer s of the upper respiratory/digestive tract.

Maier et al. (1992) investigated the occupational risk factors for cancers of the larynx in 164 cases and 656 controls. The study reported a slightly elevated risk of cancer associated with occupational exposure to cement. The estimated RR was 1.2 (95% CI 0.9-1.4) after adjustment for sm oking and alcohol consumption.

Maier et al. (1992) investigated t he occupational exposure risk factors associated with squamous cell carcinoma of the larynx. The cases, numbering 164, were all male patients attending the Heidelberg University ENT clinic with this diagnosis during the periods J une 1988 to October 1988 and November

351988 to April 1989, excluding those first diagnosed more than 3 years prior to the study periods. The controls were 656 male patients without a cancer diagnosis, half of whom attended the Hei delberg University ENT and half from the Medical Out-Patients Department of t he University Clinic. Four controls were assigned to each case, two from each of the ENT and Medical Clinics, who were matched for age (± 2 years) and size of their home. No information

on the numbers of available cases and c ontrols refusing to participate was given. Occupational and personal information was collected by interview using a computerised questionnaire. The subj ects were said to have been questioned on extent and duration of exposure to potentially harmful materials, but no detailed information on the questions, or interview conditions were given. RRs for occupational risk fact ors were estimated from odds ratios.

Regarding the types of laryngeal cancers among the cases, 72 were glottal cancers, 73 were supraglottal, and 19 could not be classified. Several

indicators of the level of education showed that average level of education was noticeably higher for controls; for example 90% of cases had no schoolleaving certificate, com pared with 74% of controls. After adjusting for alcohol and tobacco consumption, a significantly elevated estimated RR was found only for cases reporting occupational exposure to coal/coal tar products (estimated RR 2.67, 95% CI 1.3-5.5). The risk associated with cement exposure showed a marginally statistica lly significant elevation (estimated RR 1.4, 95% CI 1.1-1.6) bu t the risk was not statistically significant after adjustment for alcohol and tobacco cons umption (estimated RR 1.18, 95% CI 0.9-1.4).

This study points to the possibility of an association between exposure to cement and cancer of the larynx. As for the Maier et al 1991 study, the exposure assessment relied on the reca ll of the patients, which may have been subject to bias.

An analysis of data from what is presumed to be the same group of cases and controls investigated in the above study was included in a later publication (Maier and Tisch 1997), but this repor t did not provide any additional information on the risks of laryngeal canc er associated with cement exposure.

Maier et al. (1994) investigated the occupational risk factors for cancers of the pharynx in 105 cases and 656 controls. An elevated risk of cancer associated with occupational exposure to cement was reported. The estimat ed RR was 2.2 (95% CI 0.9-5.2) after adjustment for smoking and alcohol consumption.

In another case control study, the o ccupational exposure risk factors for pharyngeal cancer were investigated (Ma ier et al. 1994). The cases were 105 male patients with histol ogically confirmed cancer of the pharynx who consecutively attended the University of Heidelberg Department of Otorhinolaryngology/Head and Neck Surgery dur ing the period February 1991 and mid-September 1991. The controls were 656 male patients without a cancer diagnosis, half of whom attended the Hei delberg University ENT and half from the Neurological Clinics. F our controls were assigned to each case, two from each of the ENT and Neurological Clin ics, who were matched for age (± 5 years) and size and location of thei r home. Personal and occupational

36information was obtained by interview, all of which were conducted by the same interviewer. In comparison with the earlier Maier studies, more detailed employment information, including t he time spent working on particular activities, was gathered. Each subject was asked if they had been exposed, and for how long, to a number of specif ic materials/activities, including asbestos, welding fume, particular metals , cement, coal tar products, types of wood dust, herbicides, biocides, lu bricants and general dusts. RRs for occupational risk factors were estimated from odds ratios.

The percentage of cases that were c onstruction workers was 27%, compared to 7% of controls (estimated RR 4.9, 95% CI 1.3-5.9). Al cohol and tobacco consumption was much higher among case s that were construction workers

than controls who were construction wo rkers. There was a similar difference in alcohol and tobacco consumption among cases and controls from other occupations. After adjustment for alc ohol and tobacco consumption, the RR

estimate for construction workers for the risk of pharyngeal cancer was 2.8 (95% CI 1.1-5.9). W hen the analysis focused on long-term (more than 10 years) occupational contact with cement the estimated RR was elevated, at

2.2 (95% CI 0.9-5.2) after adjustment for alcohol and tobacco. The 29 cementexposed cases had a mean duration of contact with this material for 25 (SD 9.3) years. Thus, this study demons trates an increased risk of pharyngeal cancer among construction workers with long-term contact with cement, but when tobacco and alcohol consumption ar e taken into account this increased risk was not statistically significant. Overa ll, this study points to the possibility of an association between exposure to cement and pharyngeal cancer. As for the previous Maier studies, the expos ure assessment relied on the recall of the patients, which may have been subject to bias.

Maier et al. (1999) presented an overview of the results of their cancer case control study series (Maier et al. 1991, 1992 and 1994). There was no

additional information on cancer risks fo r cement-exposed workers in this report.

Maier et al. (2002) investigated the occupational risk factors for cancers of the oral cavity, pharynx and larynx in 206 cases and 110 controls, matched for smoking and alcohol consumption. A substantially increased risk of cancer associated with occupational exposure to cement was reported. The OR was 12.6 (95% CI 3.9-43.0) after adjustment for smoking and alcohol consumption.

In the most recent Maier study, occ upational and nutritional risk factors for cancers of the oral cavity, pharynx and larynx were investigated in cases

matched to controls with similar alcohol and tobacco consumption (Maier et al. 2002). The cases were 209 male Germ an patients with histologically confirmed squamous cell carcinoma at these sites attending the Heidelberg University ENT clinic. The control s ubjects were 110 male German patients attending the ENT clinic without a canc er diagnosis and matched to the cases for age, alcohol consumption and toba cco consumption. Recruitment took place over a 5-year period, between 1990 and 1995. No further details of the case and control subject selection proc edures were described, so it is not possible to assess if these procedures introduced bias. The r eport stated that access to non-cancer patients with hi gh alcohol and tobacco consumption

37was restricted and a willingness of these pat ients to cooperate was low. It was

not stated whether or not any of the cases or controls were included in the studies reported earlier. Occupation and medical histories, and information on alcohol/tobacco consumption, nutri tion and socio-economic factors were gathered by interview with the aid of a standardised questi onnaire. Specific questions were asked about exposures to asbestos, organic solvents, heavy metals, coal products, wood dust, cement, he rbicides and ionising radiation. In the analysis only those occupational subs tances to which a subject was in

contact with at least once a week fo r more than 10 years was taken into

account. It was not stated if the in terviewer was aware of the subject
case/control status.

The age distribution of cases (56 ± 9 years) and controls (58 ± 10) was

similar. The level of educational attain ment of the contro ls was higher, for example 10% of the cases and 29% of the controls attended further education institutes (such as trade school, te chnical college or university). The prevalence and type of non-cancer dis eases present among the cases and

controls were similar. Mean alcohol c onsumption for the cases (86 ± 64 g/d) and controls (97 ± 60 g/d) was similar, as was tobacco consumption (49 ± 30 pack years for cases, 56 ± 37 pack year s for controls). The percentage of cases with an occupation in the construction or demolition industries was 21%, noticeably higher that the 7% of controls. When contact with individual occupational materials were considered, regular contact with two materials showed significantly elevated odds afte r adjustment for al cohol and tobacco consumption: asbestos (OR 8.7, 95%C I 2.0-37.0) and cement dust (OR 12.6, 95% CI 3.9-43.0).

The high OR for cement dust exposure indicated a strong association with

cancers of the head and neck. A potential weakness of this study is that that the cases and controls did not appear to be comparable in te rms of education, suggesting there were socio-economic differences between the two groups. This potential confounding fa ctor was not taken account of in the analysis. Also, there may have been bias in the sele ction of controls resulting from a lack of willingness of potential controls to participate. The ex tent and direction of this bias cannot be assessed from the information presented in the report. However, the magnitude of the OR is such that confounding and bias cannot be the only explanation for its elevation.

Dietz et al. (2004) investigated the occupational risk factors for cancers of the larynx in 257 cases and 769 population controls. An elevated risk of cancer associated with occupational exposure to cement was reported. The OR was 1.18 (95% CI 0.77-1.18)assessed by substance questionnaire or 2.04 (95% CI 1.16-3.56) assessed by jobspecific questionnaire, after adjustment fo r smoking, alcohol consumption and socioeconomic status.

In a very recent case control st udy (known as the ‘Rhein-Neckar-Larynx Study’) the occupational risk factors a ssociated with squamous cell carcinoma of the larynx were investigated (Dietz et al. 2004). Eligible cases were all patients attending the Otolaryngology, Head and Neck Surgery departments of the Heidelberg, Mannheim, Lud wigshafen, Darmstadt and Heilbronn hospitals with a new, histologically c onfirmed, diagnosis of cancer of the

38larynx between May 1998 and December 2000. All laryngeal cancer patients from the study region are treated at these hospitals. Of the eligible cases, 257 (96%) agreed to participate. Three c ontrol subjects, matched for age, gender and residential location, were assigned to each case. Controls meeting the matching criteria were chosen at random from population r egistries. Of the 1233 control subjects selected, 769 ( 62%) agreed to participate. The age range of participants was 40-75 years.

Information on occupational exposures and other risk factors was obtained by face-to-face interview, using standardi sed questionnaire. Five interviewers, with special questionnaire training, were used. All cases, and 554 of the controls were interviewed at one of the participating hospitals. An occupational history of jobs held for more than 6 months was obtained, and subjects were asked if they had been exposed to a checklist of named

substances that the aut hors considered to be either known or suspected respiratory carcinogens. Detailed in formation on exposures was obtained by supplementary job-specific questions , which was used to assign semiquantitative exposure score s. Detailed information on smoking and alcohol consumption was also gathered. As a va lidation exercise, a special cement questionnaire was administered about 2-4 y ears after the original interview to subjects thought to have experienced ce ment exposure. Information on the techniques used, the types of cement used, the methods of processing cement products on-site, and for exposures to asbestos and asbestos cement was requested. Because of death, loss of contact or refusal, only 26% of eligible cases and 75% of eligible cont rols participated in the validation

exercise.

Smoking was found to be a very signific ant risk factor for laryngeal cancer. The OR for heavy smokers was 32.5 (95% CI 15.1-71.0), after adjustment for alcohol consumption. High alcohol cons umption was also a risk factor, shown by an OR 2.4 (95% CI 1. 5-9.7) for those consum ing more than 75g alcoho l per day, after adjustment for tobacco c onsumption. The occupation risk factor analysis focussed on cement exposur e. One analysis was based on the carcinogenic substance questionnaire re sponses; 23.3% of cases claimed cement exposure compared to 14.4% of controls (OR 1.18, 95% CI 0.77-1.18, after adjustment for alcohol, tobacco and socio-economic status). A second analysis considered the responses to job-specific questions and found fewer cases and controls judged to have exper ienced cement exposure; 14.8% of cases had been exposed, compared to 5.1% of controls (OR 2.04, 95% CI 1.16-3.56, after adjustment). However, there were no indications of a doseresponse when the ORs were calcul ated for low (less than 3000 cement working hours) and high (more than 3000 hours) exposure groups; the OR (after adjustment) for the low exposure group was 2.22 (95% CI 1.02-4.48) and for the high exposure group 1. 87 (95% CI 0.88-4.01).

In the validation exercise, cement expos ure of the 15 partic ipating cases was confirmed, but cement exposure was confirmed for only 69/80 (86.3%) of controls, suggesting that cement expo sure for the controls may have been overestimated. This analysis also showed that more cases had also been exposed to slaked lime (which was so metimes used in place of Portland

39cement in the 1950s and early 1960s), but the numbers of subjects was too few to draw any conclusions.

Overall, the results of this study pr ovide evidence of an association between exposure to cement and laryngeal cancer. However, this association appears weak as a dose response could not be detected and ORs, at the most, were only marginally statistically significan t. As for the Maier studies, the exposure

assessment relied the recall of the s ubjects, which may have been subject to

bias in favour of recall of ce ment exposure by the cases.

3.4.2.3 Earlier case control studies investigating risk factors for laryngeal

cancers

Earlier studies of risk factors for lary ngeal cancers, identified from a PubMed search of literature published from 1980, have been briefly considered to

determine whether there is corroborat ive evidence for the association between cement exposure and cancers at this site observed in the German
studies. Six such studies were f ound, which are summarised below.

In a Danish study, 326 cases of ne wly diagnosed laryngeal cancer were investigated (Olsen and Sabroe, 1984). Fo r each case four control subjects, matched for age and gender were identifi ed from local person-registration lists. Information on occupational history, occupational exposures, alcohol and tobacco consumption was obtained by postal questionnaire. All RRs, estimated from odds ratios, were adjusted for age, alcohol and tobacco consumption. The RR for laryngeal canc er in unskilled/semiskilled workers was significantly elevated (RR 1.8, 95% CI 1.3-2.6). The RRs for skilled and salaried workers or professionals were not elevated. Of the occupational materials, the RR was elevated only for ‘any occupational dust’ (RR 1.6’ 95% CI 1.2-2.0). The RR for exposure to cem ent was not elevated, at 0.9 (95% CI 0.6-1.3, 42 cases, 148 controls). Among 7 occupations listed with significantly elevated RRs was employment in c oncrete, cement and asbestos cement manufacture (RR 17.3). This RR relat ed to just 6 cases and 2 controls. As this grouping included asbestos cement workers, and involved a small number of subjects, no conclusions about ce ment dust can be drawn from this

observation.

Cauvin et al. (1990) studied all 2471 ca ses of squamous cell cancer of the oropharynx, hypopharynx, glottis, supragl ottis, epilarynx and oral cavity identified at a Paris hospital betw een 1975 and 1984. The controls were 147 males, who were all patients attendi ng the hospital during the study period who were healthy or with a cancer at another site. Information on occupational history, occupational exposures and alcohol and tobacco consumption was obtained by interview. The OR for t he exposure category of ‘cement, stone’ was significantly elevated for cancers at only one of nine sites analysed, the supraglossis. After adjustment for alc ohol and tobacco consumption the OR was 2.4 (95% CI 1-5.8). However, th is could be a chance finding as elevated

risk was limited to one tumour site. T he exposure group included exposure to stone, so the role of cement dus t exposure is even more uncertain.

40The possible occupational risk factors fo r laryngeal cancer were investigated on the Texas Gulf Coast (Brown et al . 1982). The cancer cases were obtained from hospital records and tumour registries at 56 (out of possible 67) hospitals in the study area. All diagnoses of laryngeal cancer for white males aged 30 to 79 living in the study ar ea during the period mid-1975 to mid 1980, totalling 303 cases, were identified. After excl usions, a group of 183 men (136 living and 47 dead) were studied. Controls were a sample of males, matched for ethnicity, age, and vital status, identif ied from various local records. Information on demographics, occupati onal history, t obacco and alcohol consumption and diet was collected by interview of participants or close relatives. Employment in the construc tion industry was one of the occupations with a significantly increased RR, afte r adjustment for tobacco and alcohol consumption (RR 1.70, 95% CI 1.06-2.72). However, this group would have been exposed to a wide range of substances so it not possible to relate this finding to cement dust exposure.

Flanders and Rothman (1982) studied 90 male cases of laryngeal cancer identified from a larger cancer st udy. The control group was 933 males

identified with cancers of the haemat opoietic system, prostate and rectum. Information on employment, tobacco consumption and demographics were obtained by interview. The alcohol and tobacco adjusted RR for employment in the construction industry was elevat ed at 1.5 (90% CI of 0.7-3.2). Among specific occupations, the RR for construction labourers was 1.3 (90% CI 0.4- 4.6). Again, this study provided no in formation specifically on cement dust as

a risk factor.

Flanders et al. (1984) studied 42 pat ients with newly diagnosed and histologically confirm ed squamous laryngeal cancer attending a US group of hospitals between 1974 and 1979. Eighty- five control subjects, matched for age, gender, residence area, tobacco and alcohol, were selected from noncancer hospital patients. Workers who may have been exposed to cement were grouped into a very heterogenous group of ‘labourer s or maintenance personnel’, which showed a significantly elevated estimated RR (4.6, 90% CI 1.6-13.6). RRs for farmers and textile pr ocessors were also elevated. This small study provided no information on t he potential for cement dust to cause

cancer.

Zagranski et al (1986) considered ma le patients attending two US hospitals with histologically confirmed lary ngeal cancer first diagnosed between 1975

and 1980 and who were alive at the time of the study (1980-1981). Controls were selected from male general surgic al patients at the hospitals, matched for year of admission, decade of birt h, county of residence, ethnicity and smoking status. After refu sals and exclusions 92 cases and were 181 controls were studied. After adjustment for toba cco and alcohol cons umption, the OR for working in the construction industry was less than 1. By occupation, the OR for ever working as a mason was elevated, at 2.2 ( 95% CI 0.9-5.8). Masons will have been exposed to dusts other than to just cement and a specific role for cement in causing laryngeal cancer cannot be identified from this study.

41Rothman et al. (1980) reviewed the epidemiology literature for laryngeal cancer. The pre-1980 literatur e did not identify cement dust exposure as a risk factor, but it must be stated that occupational risk factors had not been adequately studied at this time. The revi ew identified strong associations between both smoking and high alcohol consumption and laryngeal cancer.

Overall, the earlier studies of risk fact ors for laryngeal cancer provide limited support for the existence of an as sociation between working in the construction industry and laryngeal cancer, but provide no useful information

about the risks associated with exposure to cement dust per se

.

3.4.2.4 Other recent mo rtality and cancer-related st udies involving subjects with exposure to cement dust.

These studies have only limited rele vance to the assessment of the hazardous properties of Portland cemen t, and are only briefly considered.

Potential occupational risk factors for multiple myel oma were investigated in Swedish construction workers (Lee et al. 2003). Incident cases of multiple myeloma for the period 1971-1999 am ong 365,000 members (about 80% of eligible workers) of a Swedish constr uction industry health care scheme were
identified from the Swedish Cancer Registry. Occupational exposures were assessed in a semiquantitative manner on the basis of industry job codes. A total of 446 primary multiple myeloma cases were identified. The RR for cement exposure 1.0 (95% CI 0.76-1.28, 49 cases) after adjustment for age and body mass index, showing than cement was not a risk factor for multiple myeloma.

Szadkowska (2001) conducted a nested case control study in pulp and paper workers. Three cases of lung cancer among persons with previous exposure to ‘cement, brick, sand, grindstone dus t’ were identified, compared with none with such exposure among controls. No conclusions about the effects of cement dust can be drawn from this study.

A retrospective cohort mortality was conduc ted in members of a US plasterers and cement masons trade union (Stern et al. 2001). All members dying during the periods 1972-1980 and 1984-1996 were included. There were 7811 cement masons in the cohort, whose exposures were said to include cement dust, silica, asphalt and various solvents. Compared to the general population, cement masons had significantly higher mortality for cancer of the stomach (proportionate cancer mortality rati o 133, p<0.01) and for benign neoplasms (proportionate mortality ratio 132, p<0. 01). Because of the wide range of occupational exposure experienced by the cement masons no conclusions

about the effects of cem ent dust can be drawn.

Krstev et al. (1998) conducted a death cert ificate based case control study of prostate cancer in 24 US States. T he occupations of 60900 men with prostate

cancer as a cause of death were i dentified and compar ed with age matched

controls that had died of causes ot her than cancer. ‘Supervisor of brick

42masons’ was one of over 70 occupations with a significantly increased odds ratio for prostate cancer. The extent of cement exposure experienced by this occupational group was not reported.

Cancer in Illinois construction workers was investigated in a series of case control studies using subjects from the state Cancer Registry (Keller and Howe 1993). The risk of lung cancer was greater for construction workers than the general population of Illinois (OR 2.11, (95% CI 1. 02-1.26), but this was thought to be due to higher tobacco consumption among the construction workers. Cement exposure was not i dentified as a risk factor for cancer.

In a briefly reported study, the frequenc ies of sister chromatid exchanges (SCEs) in the lymphocytes of workers from an Indian Port land cement factorywere measured (Fatima et al 1995). The exposed subjects were 59 nonsmokers, age range 24-54 years, who had been exposed to cement for 1-17 years. The mean number of SCEs in t he exposed workers was 8.98 per cell, compared with 3.5 among the controls. Wi thin the exposed group the results were analysed according to whether the subjects had been exposed for 1-5, 6-11, or 12-17 years. T he frequency of SCEs appeared to be positively related to exposure duration, but this could have been due to age differences between the exposure groups, which were not taken account of in the analysis. This is a briefly reported inve stigation, with resu lts that are without

corroboration from other st udies. Furthermore, the health significance of such an increased frequency of SCEs is not known. Therefore, no conclusions about the hazardous properties of cement du st can be drawn from this study.

3.4.2.5 Summary of mortality and canc er studies involving workers with longterm exposure to cement dust

HSE (1994) came to a posit ion that there was no c onvincing evidence for an increased incidence of any site-specific cancer resulting from cement exposure, but acknowledged that the data available at that time were not consistently and reassuringly negative. Since the early 1990s, a number of relevant cancer cohort and case control studies have been published, conducted in groups exposed to cement ei ther through employ ment in cement manufacturing or in the construction i ndustry. These studies have identified associations between cement exposure and cancers at several specific sites: the stomach, lungs, colon, and head/neck. The support for a causal

association of each of these cancer s with Portland cement exposure is discussed with reference to strength of as sociation, consistency, the presence of a dose-response relationship and bi ological plausibility. Evidence from experimental studies in animal or in vitro models, which can contribute to arguments for or against causality, are not available.

Elevated SMRs for stomach cancer were seen in three out the four cohort

studies conducted in cement manufact uring workers covered by HSE (1994). One cohort study in cement manufactur ing workers included in this review, conducted in Lithuania, identified a dose-related trend towards an increased risk of stomach cancer, although the numbers of cases involved was very small. In contrast, cohort studies conduc ted in two Swedish Portland cement

43plants and a Danish cement plant did not show increased risks for stomach cancer. There is a degree of consist ency, since an association has been seen

in four out of the six av ailable cohort studies. The st rength of association is moderate, with SMRs ranging from 1.19 to 1.77. In two studies there was evidence for a dose-response relationship, but the evidence was far from convincing because of the small number of cancer cases in each exposure subgroup. Overall, the case for causalit y is stronger than for the cancers at other sites, but the recent data does not change the picture of uncertainty presented in the early 1990s.

An association between cement expos ure and lung cancer was seen in a cohort study in Lithuanian cement manuf acturing workers but this could have been due to smoking. A study in Icel andic cement masons showed an increased risk of lung cancer in comparison with the general population, reporting an SIR of 1.77 (95% CI 1. 01-2.88) when allowing for a latency period of at least 30 years. Overall, evidence for causality is very weak because consistency across studies in different populations is lacking. Furthermore, the strength of the observed association was moderate, and dose-response information is not available.

A comprehensive cohort investigation into cancer at two Swedish cement manufacturing plants showed an increased risk of right-sided colon cancer among workers with long-term cement expo sure. However, the right side of the colon, or colon generally, was not i dentified as a cancer site associated with cement exposure in the other c ohort studies. Again, evidence for causality must be considered to be weak because an association has not
been observed in studies in different populations. However, the strength of association was greater than found for colon and lung cancers (SIR 4.3, 95%
CI 1.7 - 8.9 for workers with more than 25 years exposure) and there was some evidence suggesting an increas ed risk with increasing duration of

exposure.

Concerning cancers of the head and neck, a series of recent population

based case control studies conduced in Germany demonstrated an

association between contact with cement through employment in construction and cancers at these sites, especially cancers of the pharynx and larynx. Earlier case control studies, conduct ed elsewhere, inve stigating the risk factors for laryngeal cancers provided limited evidence of an association between employment in the constructi on industry and an increased risk of laryngeal cancer, but these studies provided no useful information on the risks associated with exposure to cement per se. No information on the association between these types of cancer and ce ment can be derived from the cohort

studies because head and neck cancers are rare and the cohort studies lacked the power to investigate such cancers. The strength of association between occupational contact with cement and cancer of the head and neck was generally moderate, with ORs or es timated RRs ranging from about 1.2 to 2.4, although for one study the associat ion was very strong as shown by an
OR of 12.6. The association showed cons istency within the series of studies conducted in southern Germany but onl y limited corroborative support is available in terms of consistency from studies of laryngeal cancer in other

44populations. A dose-response relationship has not been demonstrated. Furthermore, the exposure assessments in these studies did not determine the quantitative nature of t he cement exposure, or take account of other exposures that could be experienced by persons who have occupational contact with cement, so ther e is no clear picture of what the subjects were exposed to. Overall, evidence for a causal association between cement exposure and head and neck cancer is weak.

Biological plausibility is considered as for all cancers together. As a highly alkaline substance, cement can cause irrita tion at sites of contact, such as the mouth, throat, and lungs. Persistent chronic irritation will cause repeated cycles of cell death, cell pr oliferation and other infla mmatory responses. It is recognised that this process can be a st ep on the pathway to cancer. Thus it is biologically plausible that cement dust could have the potential to cause

cancers at sites of contact.

To conclude, a causal association between Portland cement exposure and

cancer has not been established. Nevert heless, the findings of the recent

studies reviewed in this document main tain the uncertainty concerning a possible risk of cancer raised by the ear lier data reviewed by HSE (1994).

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50Table 1 Summary of recent studies of non-malignant respiratory disease in workers with long-term exposure to cement dustReferenceCountryStudy subjectsMain investigationsMain findings in cement workersFell et al. 2003Norway119 cement factory workers, mainlyretired. 50 blue collar controls,Respiratory questionnaire, spirometry.Current dust measurements.No differences in respiratory health between cementworkers and controlsmatched for ageMwaiselage etTanzania115 cement factory workersSpirometry, peak flow. Current dustReduction in FVC, FEV1, FVC/FEV1, PEFR, negativeal. 2004102 controls, with maintenance ormeasurements.correlation with cumulative exposure estimatesoffice jobs at factoryLaraqui HossiniMorocco280 cement factory workers. 73Respiratory questionnaire, spirometry. NoHigher prevalence of respiratory symptoms and minoret al. 2002controls with office jobs.exposure data, but dust levels high.spirometry deficitsMeo et al. 2002Pakistan50 cement factory workers. 50Spirometry. No exposure informationReduction in FVC and FEV1. Increase FEV1/FVC ratio.matched population controls.Al-Neaimi et al.UAE75 cement factory workers. 134Respiratory questionnaire, spirometry.Higher prevalence of respiratory symptoms. Reduction in2001matched controlsNo exposureinformation.FVC, FEV1and FEV1/FVC ratioNoor et al. 2000Malaysia62 cement factory workersRespiratory questionnaire, spirometry.Higher prevalence of respiratory symptoms. Reduction in70 controls from university.Current dust measurements.FVC, FEV1and FEV1/FVC ratio.Mengesha et al.Ethiopia53 cement factory workers. 211Respiratory questionnaire, spirometry,Higher prevalence of respiratory symptoms. FEV1and1998controls, non-dusty occupationspeak flow. Current dust measurements.FEV1/FVC ratio lower in the group with highest cementexposure.Abuhaise et al.Jordan348 cement factory workers,Respiratory questionnaire, spirometryHigher prevalence of asthma in those with highest1997divided into 3 exposure groupsCurrent dust measurements.exposure. Spirometry similar for all 3 groups.Chanrawanshi &India365 cement factory workers. 45Peak flow. No exposure informationPEFR lower among cement workers who worked rotatingPati 1996controlsshiftsYang et al. 1996Taiwan412 cement factory workers. 147Respiratory questionnaire, spirometryHigher prevalence of respiratory symptoms. Reduction incontrols with office jobsCurrent dust measurementsFVC, FEV1and FEV1/FVC ratioYang et al. 1993Taiwan661 cement factory workers,Respiratory questionnaire, spirometry.Higher prevalence of one respiratory symptom in thoseincluding 146 office workersCurrent dust measurementswith highest exposure. No differences in spirometrymeasurements.Abrons et al.USA2640 cement factory workers. 1458Radiography. Current dust measurementsIncrease prevalence of radiography-detected minor1998blue collar controlsavailableabnormalities of lungs, confined to mainly to smokersAlvear-Galindoet al. 1999Mexico425 cement factory workersRespiratory questionnaire. Semi-quantexposure assessmentPrevalence of respiratoryproblems highest among thosewith highest exposure scoresAbou-Taleb etUAE304 cements factory workersRespiratory questionnaireChronic cough in 19%, chronic bronchitis in 12% ofal. 1995workers, but no control group for comparisonLaraqui et alMorocco120 concrete factory workers. 120Respiratory questionnaireHigher prevalence of respiratory symptoms among2001controls, civil servantsconcrete workers51Fell et al. (2003) is a retrospective cohortstudy, the remainder are cross-sectional studiesTable 2: Summary of mortality and cancer morbidity studies in cement manufacturing workers or masonsReferenceCountryStudy subjectsMain investigationsMain findingsJakobsson et al.1993Sweden2400 cement factory workers,at two plantsMortality and cancermorbidity, compared toOverall mortality and cause-specific non-malignantmortality for the cement workers was not affected.general populationRisk of tumours of right side of colon increased (SIR2.7, 95% CI 1.4 - 4.8).Jakobsson et al.1994Sweden1526 cement factory workers3965 blue collar workersMortality and cancermorbidity, compared toRisk of tumours of right side of colon increased forcement workers (SIR 2.6, 95% CI 1.4-4.6).8092 fishermengeneral populationCancer risks for other groups similar to that of thegeneral populationVesbo et al. 1991Denmark546 cement factory workersCancer morbidityNo evidence of an increased risk of cancer for856 unexposed controlscement workersSmailyte et al. 2004Lithuania2498 cement factory workersMortality and cancermorbidity, compared togeneral populationIncreased incidence of lung cancer among cementworkers (SIR 1.5, 95% CI1.1-2.1), but smoking wasnot taken account of in the analysis. Dose-relatedtrend towards an increased incidence of stomachcancer.Rafnsson et al. 1997Iceland1172 masons, using wetCancer morbidity, comparedIncreased incidence of lung cancer among masonsconcrete to finish buildingsto general population(SIR 1.7, 95% CI 1.1-2.5)52Table 3 Summary of German case control studies for cancers of the oral cavity, pharynx and larynxReferenceLocationStudy populationMain findingsMaier et al. 1991Heidelberg,Gliessen200 male cases of cancer of the oral cavity,pharynx and larynx800 male hospital patient controls, matched forage and size of homeElevated risk of cancer associated with occupational exposure tocement. Estimated RR 2.4 (95% CI not stated) after adjustment forsmoking and alcohol consumptionMaier et al. 1992Heidelberg164 male cases of cancer of the larynx656 male hospital patient controls, matched forage and size of homeSlightly elevated risk of cancer associated with occupationalexposure to cement. Estimated RR1.18 (95% CI 0.9-1.4) afteradjustment for smoking and alcohol consumptionMaier at al. 1994Heidelberg105 male cases of cancer of the pharynx656 male hospital patient controls, matched forage and size/location of homeElevated risk of cancer associated with occupational exposure tocement. Estimated RR 2.2 (95% CI 0.9-5.2) after adjustment forsmoking and alcohol consumptionMaier et al. 2002Heidelberg209 male cases of cancer of the oral cavity,pharynx and larynx110 male hospital patient controls, matched forage, smoking and alcohol consumptionSubstantially elevated risk of cancer associated with occupationalexposure to cement. The OR was 12.6 (95% CI 3.9-43.0).Dietz et al. 2004Rhien-Neckarregion257 cases of laryngeal cancer769 controls from the general population,matched for age, gender and location of homeElevated risk of cancer associated with occupational exposure tocement. The OR was 1.2 (95% CI 0.8-1.2) assessed by substancequestionnaire or 2.0 (95% CI 1.2-3.6) assessed by job-specificquestionnaire, after adjustment for smoking, alcohol consumptionand socio-economic status.53