OCCUPATIONAL HEALTH AND SAFETY IN UTILIZATION OF LIGNOCELLULOSIC BIO-POZZOLANS IN THE CONSTRUCTION INDUSTRY

ignocellulosic bio-pozzolans (LBPs) are either produced by open-air incineration or as industrial byproducts and can be used for soil stabilization and in making concrete for road construction. The preparation of the LPBs involves the collection of raw materials/wastes, drying, incineration, grinding, and sieving to a required size before utilization for construction works or products. The finer the LBPs, the more reactive they become, and the higher the potential binding properties. Coarse LBPs are less reactive; and therefore, exhibit low binding properties with reactions. Very fine LBPs are essentially nanomaterials and can be an occupational health and safety hazard to workers handling these materials. In this review, the LBPs production process was briefly clarified, and potential hazards and risks were investigated. Silicon Dioxide (SiO 2 ), the main chemical compound present in LBPs, was noted to potentially have a significant health hazard to humans. SiO 2 exposure is reported to induce deoxyribonucleic acid (DNA) destruction. This study recommends an airborne exposure limit of 2mg/m 3 for LBPs, and the ACGIH exposure limit recommendation for SiO 2 .


INTRODUCTION
Occupational Safety and Health (OSHA) at work are vital elements for a decent job, as contended by the International Labour Organisation (ILO). Occupational accidents have a trivial human, social and economic cost, which should be eliminated by ensuring that all workplaces are safe. According to the ILO's latest data on annual fatal casualties from a number of countries, the United States recorded the highest number of fatal casualties ( Figure 1) while Cuba recorded the highest number of calendar days during which workers were temporarily incapacitated and unable to work due to fatal injuries( Figure 2) (ILO, 2022). Norway was the least with zero days lost (2019), while the United States had 9 days lost (2014).
Significant fatal injuries and the subsequent loss of working days, have led most countries to develop and ratify occupational health and safety regulations. These include regulations for the safety and health of workers in the construction industry (Rubio et al., 2023). Occupational health and safety continuous improvement (OHSCI) in modern construction is important (Alkaissy et al., 2022;Araújo et al., 2022;Mavroulidis et al., 2022;Mohandes et al., 2022) This is especially important while undertaking civil engineering works, which involve the use of cement and other cementitious materials. Conventional cement production, transportation, and usage lead to significant production of greenhouse gases such as CO2, and now there are increased calls to reduce CO2 emissions. However, it is essential to note that efforts are being made to study and develop alternative cement with a low CO2 footprint (Abdalla et al., 2022;Caronge et al., 2022;Cormos, 2022;Kremer et al., 2022;Majchrzak-Kucęba et al., 2022;Nie et al., 2022;Santos et al., 2022;Syahida Adnan et al., 2022;Türkeli et al., 2022;Zhuang et al., 2022).
Other ways of reducing CO2 from cement manufacturing include research on a laboratory and pilot scale to study supplementary cementitious materials (SCMs) that can potentially replace the use of conventional cement in construction. The SCMs are proven environmentally friendly materials. Some of these SCMs are the lignocellulosic bio-pozzolans (LBPs) produced through open-air incineration. They include Rice Husk Ash (RHA) (Jittin and Bahurudeen, 2022;Mohamed et al., 2022) which can be used in various construction applications like soil stabilization for road works, production of concrete and associated concrete products like concrete blocks, bricks, and paving blocks.
The preparation of the LPBs involves collecting raw materials/wastes, drying, incineration, grinding, and sieving to a required size before utilization. Generally, the finer the LBPs, the more reactive they become, and the higher the pozzolanic properties. Coarse LBPs are less reactive and have low and slow reactive pozzolanic properties.
Very fine LBPs are essentially nanomaterials and hence pose a health risk to both the researchers and the user of these materials. Tetley (2007) observed that the material composition of LBPs might have negative health impacts on human organs like the lungs, brain, and liver.
It is further noted that LBPs contain substances listed as hazardous by the International Agency for Research on Cancer (IARC). There is no universal standard for monitoring the exposure of both researchers and workers to these dangerous substances. This paper briefly explains the LBPs production process, highlights the chemical composition and classification of LBPs, and identifies and discusses the main hazardous substances in LBPs. It also provides recommendations for both exposure limits and reduction of exposure to hazards contained in these materials. Data compiled in this paper will significantly contribute to safeguarding the health of researchers undertaking studies on the application of LBPs in construction works. It will also enhance the safety and health of workers that will handle and apply LBPs in actual construction works. Figure 3 shows the general LBPs production process, which requires minimal mechanization. Open-air LBPs production involves collecting raw materials which can be ordinary agricultural wastes. These are then sun-dried to ensure minimal moisture content for ease of burning. The material is burnt in the open air on a hard surface to enable the accumulation of ashes. The ashes are then left to cool. The cooling time depends on the amount of ash and environmental conditions like humidity, wind, and temperature. After cooling, the material is ground and then sieved to a recommended sieve size before being used as a pozzolanic material for making concrete or concrete products like blocks or soil stabilization.

COMPOSITION
The chemical composition of some of the LBPs from different plants and different research is detailed in Table 1 (Aluga and Kambole, 2020). The main chemical compound in LBPs is silicon dioxide (SiO2), followed by calcium oxide (CaO), as shown in Figure 4, derived from Table 1. Sodium Oxide forms about 1% of the LBPs.

SUBSTANCES
The main compounds/substances in the LBPs from Table 1 Table 2 details the occupational hazards and exposure limits to (LBPs) and suggests the exposure reduction of the above-named seven (7) substances found in the LBPs. Accordingly, the LBPs affect humans when breathed in due to occupational exposure. The following are some of the health and other effects identified when exposed to The workplace exposure to these compounds differs from one compound to another, as detailed in Table 2.
Wearing respirators, putting on protective work clothing, regular bathing after using the substance, and detailed warning information in the work area are some methods suggested for limiting exposure to LBPs.