Occupational exposure to reinforced concrete production is associated with adverse respiratory health

By Vijay Kumar MalesuReviewed by Lily Ramsey, LLMSep 21 2023

In a recent study published in BMC Public Health, researchers investigated the exposure to fine particulate matter (PM) in reinforced concrete production environments and its impact on respiratory health and lung function among industry workers. 

Study: Occupational exposure to fine particulate matter in the reinforced concrete production and its association with respiratory symptoms and lung function. Image Credit: wrangler/Shutterstock.com

Background 

In nations like Russia and Kazakhstan, occupational diseases, particularly respiratory ones such as chronic obstructive pulmonary disease (COPD), are prevalent, with up to 15% being preventable if workers were not exposed in their workplaces.

Contributing factors include cigarette smoking, subpar exposure control measures, and environmental pollution. With the decline of large-scale industries in former Soviet states, many workers transitioned to artisanal production, often without proper exposure controls.

The shift towards artisanal production potentially obscured the real impact of occupational exposures on respiratory health.

In Almaty, Kazakhstan, 25% of the population has encountered industrial contaminants, prominently from the reinforced concrete parts industry, which involves cement processing and metalworking, both aerosol-generating. Despite the known hazards of cement and welding, risks specific to this industry remain underexplored.

Considering its pivotal role in infrastructure development and anticipated growth in Central Asia, it is imperative to delve deeper.

There is a pressing need for further research, given the limited insight into the exposure levels and health implications linked to reinforced concrete production, especially with its dual exposure potential to cement and metal aerosols.

About the study

In Almaty's industrial zone, a 7.52-hectare reinforced concrete plant employing 198 staff was studied for exposure in its production cycle, including concrete mixing, armature shop, metalworking, and molding workshops. An office nearby served as a control for potential environmental factors.

In summer of 2023, to avoid ambient air pollution bias in Almaty, exposure data was collected from five plant locations using portable PM_2.5 filters and cyclones, resulting in 50 personal samples.

Sampling spanned six to eight hours daily and was collected using a battery-powered pump, with the device fixed in the workers' breathing zone. Filters were weighed before and after to determine PM_2.5 concentrations while all processes adhered to State Standards.

Workers at an industrial plant in Almaty underwent a study that received ethical clearance from the al-Farabi Kazakh National University's Committee on Bioethics.

Every participant provided informed written consent and completed a structured questionnaire available in both Russian and Kazakh. This aimed to obtain detailed work histories information on personal habits such as smoking, alcohol consumption, physical activity, and respiratory symptoms.

Smoking habits were categorized as current, former, or never smoking, while physical activity was defined as exercising at least three times a week for a minimum of 40 minutes.

The COPD Assessment Test (CAT) and the modified Medical Research Council (mMRC) scale were employed to gauge respiratory health. Scores from these were used to determine symptoms and the extent of dyspnea.

Moreover, workers underwent spirometry testing after abstaining from smoking for at least two hours. The results gave insights into vital capacities (VC) like forced VC (FVC) and forced expiratory volume in a second (FEV1).

Any participant with an FEV1/FVC below 0.7 was administered salbutamol and tested again using a specific spirometer, with no participant on regular respiratory medication.

For statistical analysis, the primary interest was determining if workplace PM_2.5 exposure was linked to respiratory symptoms and lung function.

Various tests, like the Shapiro-Wilk, Mann-Whitney U-test, χ2 test, t-tests, and Kruskall-Wallis, were employed to analyze the data.

Exposure data were collated for all work sites and, alongside factors like smoking and work duration, were used in linear regression models to explore any potential association with respiratory symptoms, utilizing the NCSS 2021 software and considering a p-value below 0.05 as significant.

Study results

Of the 198 permanent staff at the reinforced concrete products plant in Almaty's industrial zone, 162 participated in the study, resulting in an 82% response rate. The average participant was in their 40s and had worked for about 19 years.

There was a strong correlation between age and total years worked (r = 0.91), but the time spent working at this specific plant had a weaker relationship with age and overall service years.

Over half of the workers were either current or former smokers (58%), a majority consumed alcohol (61%), and a significant number were not physically active during their free time (79%).

It was observed that employment duration varied among different departments, with the administrative office staff having the shortest tenure, followed by those in the molding workshop.

In August 2023, 50 PM_2.5 samples were collected from four production workshops and a non-production location (the office). The least variation was in the office, with concentrations ranging from 17 to 45 µg/m³.

The concrete-mixing unit had the highest exposure, with concentrations ranging from 980 to 1,670 µg/m³, followed by the metalworking unit, mainly involving welding and metal cutting, showing a median PM_2.5 concentration of 510 µg/m³. In contrast, the armature and molding workshops had the lowest PM_2.5 exposure among production areas.

There was a stark contrast in aerosol exposure when comparing the office to the concrete-mixing unit, with the latter having nearly 40 times the median concentration. Statistical analysis of these locations revealed a highly significant difference in median PM_2.5 concentrations.

Regarding respiratory health, the CAT score, used to assess respiratory symptoms, was generally low across participants, indicating minimal respiratory issues. Only five workers from production had scores above 10, indicating a notably low prevalence of respiratory symptoms in the overall group.

Chronic bronchitis was the most common self-reported diagnosis, found in almost 11% of participants. Although only one worker claimed to have COPD and none reported asthma, spirometry tests revealed 11 undiagnosed cases of COPD.

Cumulative PM_2.5 exposure ranged considerably among workers, with significant differences noted between various groups. Regression models revealed associations between higher CAT scores and factors like age, gender, smoking habits, cumulative PM_2.5 exposure, and a history of chronic bronchitis.

After adjusting for confounders, factors like cumulative PM_2.5 exposure, gender, current smoking status, and chronic bronchitis remained significantly associated with CAT scores. Current smokers had notably higher CAT scores and lower FEV1/FVC ratios.

While occupational groups did not influence CAT scores, there was a significant difference in FEV1/FVC ratios, with the metalworking group showing a lower ratio than office workers.