Cementing Respiratory Research
Published: 21st Jan 2013
Obstructed airways or reduced lung function and respiratory diseases are still found to a high degree in certain workplaces. The United Nations agency, the International Labour Association (ILO), has estimated that workers, on a global scale suffer around 160 million occupational diseases, and two million deaths each year. Fatalities due to respiratory diseases constitute around 140,000 of these.
Given the same statistics, around 11 million out of the total occupational diseases are respiratory diseases. Often dramatic cases receive public attention through media and social media, but the everyday reality is that most workers who die, or fall ill due to occupational diseases, do so largely unnoticed.
These diseases and fatalities have a high human cost, and a high economic price related to loss of productivity, which both organisations and enterprises as well as workers are well aware of.
Respiratory diseases such as emphysema, work related asthma and chronic obstructive pulmonary disease (COPD) are still challenging the working life of many workers, resulting in both illness and disability.
Respiratory diseases are imposing heavy burdens both for the personnel facing the illnesses, the businesses losing their experienced personnel and the society bearing the overall costs when it comes to early retirement and healthcare.
Increased knowledge about occupational exposures affecting the respiratory system is therefore of great importance, in order to implement suitable preventative measures. For primary prevention, this relates to cessation or reduction of exposure to the harmful agent in question. For secondary prevention, an important tool will be the use of personal protective devices, and especially suitable respiratory protective equipment.
Prevention of occupational respiratory diseases
These challenges have recently been addressed in a comprehensive, international study of lung function among 4,500 cement production workers. Knowing whether the cement aerosol particles, in this case, are inhalable, thoracic or respirable tells us something about what kind of equipment will ensure a high quality protection.
In order to assess the risk properly and thus introduce the correct preventive measures, one needs to know if the typical range of particles are inhaled deep into the alveoli of the lungs, or if they are of a size where they deposit in the mouth or throat.
Cement and cement production
Cement is a binder, a substance that sets and hardens independently, and that can bind other materials together. The most important use of cement is to bind natural and artificial aggregates to form strong building materials. This kind of bonding occurs in fields such as construction, agriculture, water management, transport and many others. Thus, the cement industry provides building material for land-based and offshore installations.
Cement is typically produced by heating a homogenous blend of limestone and clay, which is then adjusted to a suitable content of calcium, silicon, aluminum and iron in a kiln. During its heating to 1,450° C, clinker is formed. The clinker contains calcium silicates, calcium aluminates and calcium ferrites.
Clinker is subsequently ground with gypsum and other additives, resulting in a fine particulate powder called cement. In contact with water, clinker partly dissolves and forms an aquaeous slurry of high alkalinity, giving clinker and cement strong irritant properties.
Cement production workers are exposed to airborne particles of raw materials, clinker, additives and to the final cement product, and their work has been linked to changes in lung function and airway obstruction. Importance of this research project
The relationship between cement dust exposure and respiratory effects has been fairly extensively examined, but mainly in cross sectional studies. Overall, the pattern of evidence clearly indicates that occupational exposure to cement dust has produced deficits in respiratory function.
The evidence available at the present time is insufficient to establish with any confidence the dose-response relationship for these effects, however. The effects of long term exposure remain poorly studied, particularly because there are no longitudinal prospective studies in workers exposed to cement.
The National Institute of Occupational Health in Norway has recently performed an extensive study on workers at cement factories throughout Europe. Twenty-four cement production facilities in eight different countries in Europe, involving some 4,500 employees have been included in a four year follow-up study.
This cohort study was initiated by the European Cement Association, the CEMBUREAU, and is currently being performed by the National Institute of Occupational Health in Norway in collaboration with the University of Oslo, Oslo University Hospital and the University Tor Vergata in Rome, Italy.
The objective of the study was to characterise the exposure for the dust fraction inhaled to the central airways and lungs (the thoracic dust fraction) during the production of cement and to relate cement dust exposure levels to potential health outcomes such as reduced lung function and other airways symptoms.
Information on the exposure was established through exposure assessment using personal exposure measurement of the thoracic fraction of workplace aerosol in order to establish a job exposure matrix.
In the study, selected workers carried personal exposure measurement equipment through one or more full day work shifts. The different tasks performed during these two workdays were recorded in an exposure log.
Information on health outcomes was gathered from the participants by the repeated use of spirometry, which is the most common of the pulmonary function tests, and the use of an approved health questionnaire.
Since exposure may differ at different times of the year due to climatic variations (wind and humidity as well as temperature), the study was planned to include plants in different regions, and the sampling was performed at different times of the year, all in all to have the best possible coverage of the real variations of potential exposure.
The cement production facilities involved in the study are situated in the following countries: Estonia, Greece, Italy, Norway, Spain, Sweden, Switzerland and Turkey.
Reduced lung function and airway obstructions
There is agreement on the fact that cement dust can cause reduced lung function and increased prevalence of certain airway symptoms in cement workers, but the details known today do not provide information on what exposure levels prompt such effects.
Reduced expiratory flow rates and volumes show acute reductions after exposure to aerosols. Prolonged effects in these conditions are also demonstrated in scientific literature. Other reported findings are, among other things, rhinitis, chronic productive cough, dyspnea, wheezing, and chest radiographic abnormalities.
The risk of COPD in relation to exposure to cement dust has also been discussed, but findings suggest that there is not a clearly observed excess of COPD in exposed workers compared to controls in published studies. At the same time, one can argue that if there is an affect on the dynamic lung volume, there will be an affect on the COPD frequency.
The precautionary principle
Personal protective equipment may reduce exposure, as long as equipment is chosen, fitted and used properly. The American Occupational Safety and Health Administration (OSHA) states this in their standards for Respiratory Protection and Eye and Face Protection.
Although following the OSHA guidelines is a step towards ensuring workers’ safety, current thinking and newer workplace safety codes suggest it is also necessary to use engineering controls on power tools and production lines to collect and dispose of dust - in other words, to reduce dust exposure as a number one priority.
Newer research also indicates that concentrations below the occupational exposure limits (OEL) may cause airway inflammation. The present Norwegian OEL is 5 mg/m3 for respirable dust and 10 mg/m3 for total dust. Although the consequences are uncertain, and need to be followed up, recent studies indicate that inflammatory effects may occur at dust exposure levels below 1 mg/m3.
Respirators and breathing apparatuses are used in many workplaces to protect workers when working with hazardous substances, such as gases, solvents, powdered chemicals and sprays. The protective equipment is constructed of various elements which cover the face. Among these, the most commonly used solutions are helmets, visors, hoods and masks.
Respiratory protective equipment is most often thought of as the last (ultimate) option after having taken other reasonable steps to control the exposure to hazardous materials, and improve air quality and ventilation in the work area.
The use of respiratory protective equipment should only be set up after performing an adequate risk assessment. In working life one may argue that it is well worth using a mask even if a risk assessment has not yet been performed, in order to prevent potential risk.
Protective equipment and cement
Different hazards and exposure situations require different kinds of protective equipment, and normally when it comes to cement work protective guides propose gloves, long sleeves and covering clothes and regular washing of garments to avoid cement burns.
Related to respiratory protective equipment, one finds little regulation when it comes to cement. One has to consider that cement dust may range from ultrafine particles to very large particles - above the inhalable.
Karl-Christian Nordby, MD, PhD and project leader for the Norwegian research project said: “Knowing that inhaled particles can penetrate and deposit in different parts of the human respiratory system - from the nose and mouth to the bronchi and alveoli of the lung - it is of importance to perform an adequate risk assessment, make use of engineered protective equipment and, if and when needed, to make use of adequate respiratory protective equipment.”
In another project, markers of inflammation and short term effects of the exposure to cement dust on dynamic lung volumes and gas diffusion has been studied. Here, the workers at the different plants were examined before and after a working shift, where the workers were exposed to cement and cement production related dust for a full shift of eight hours.
Health examinations - spirometry - and a questionnaire related to work tasks were filled in on the same day as the exposure measurements were taken. The dust collected consisted of respirable, thoracic and inhalable aerosol fractions.
This study on inflammatory markers observed the exhaled air and blood, which has not been subjected to study before in this setting, and predicts that some short term effects may be present, and thus strengthens the indications from earlier cross sectional studies that observed effects from exposure to dust may possibly stem from inflammatory activity in the lung.
Results from the four year follow up study
The four year follow up study, Prospective Monitoring of Exposure and Lung Function among Cement Workers, was conducted by the NIOH Norway and collaborating institutions, and is now in the wrap-up stage. Several new publications are expected in 2013.
The findings of this project are so far corroborating research in earlier studies when it comes to the indications on early airway inflammations and reduced lung function, and thus support the hypothesis that exposure to dust in cement production may possibly lead to respiratory symptoms and airway obstruction.
At the same time, it is well appreciated that cross-shift studies may be more prone to bias than longitudinal studies, and that the latter may provide more reliable knowledge than the former. The upcoming publications will therefore be followed closely by the European cement industry in particular, along with the providers of occupational safety and health services.
To have clear cut knowledge of what exposures might cause illnesses and, in the longer run, diseases, or the potential for a higher staff turnover in the workplace due to such exposure, is of great importance in order to be able to set the appropriate preventative measures.
Published: 21st Jan 2013 in Health and Safety International