Assessing Dust Emissions, Health Impacts, and Accident Risks in Prefabricated and Conventional Construction: A Comprehensive Comparative Study

Abstract

All over the world, construction accidents and respiratory diseases are among the most important problems. The prefabricated system is an introduction to reduce emissions and accidents during the construction phase. However, there is a lack of research that proves the superiority of the prefabricated system in terms of both dust health impacts and accident risks simultaneously. Therefore, this study conducts an assessment in terms of dust health impacts and accident risks to compare the prefabricated system and the conventional system. This research is carried out in the following steps. (i) collection of data, (ii) calculation of dust emission, (iii) health impact assessment, and (iv) calculation of accident risk. The conventional system produced 5,454,527.43 kg of dust, had a willingness to pay $12,631.40, and caused 4.87 × 10² injuries and 8.05 × 10² fatalities, while the prefabricated system produced 2,711,423.72 kg of dust, had a willingness to pay $6282.02, and caused 3.45 × 10² injuries and 5.69 × 10² fatalities. The results show that when the prefabricated system is applied instead of the conventional system, the dust emission, health impact, and risk level can be reduced by 38.59%, 43.04%, and 29.03%, respectively. This study contributes to previous knowledge when decision-makers select prefabricated systems over conventional systems. Furthermore, it provides insights into the health and safety impacts of both construction methods and the necessary measures to mitigate these impacts.

1. Introduction

Off-site construction has become one of the most prominent construction methods in the construction industry. It involves the planning, designing, fabrication, transportation, and assembly of the fabricated building items on the construction site [1,2]. Recently, prefabricated structural systems, one of the off-site construction methods, have been widely used in the construction industry because of their diverse benefits over conventional structural systems in areas such as productivity [3,4,5], environmental impacts [6,7,8,9], cost [7,8,10,11], quality and safety [12,13]. Prefabricated systems for construction are rapidly gaining popularity in the Republic of Korea as more factories are built to meet the rising demand for semiconductors and other products [6]. Moreover, in terms of residential buildings, the use of prefabricated systems has increased since 2017 as the Korea Institute of Civil Engineering and Building Technology started promoting the use of modular for public housing projects [14].

In addition to its impact on productivity, cost-effectiveness, and quality, the construction industry is also subject to stringent legal regulations aimed at ensuring worker safety and minimizing environmental harm [15,16,17]. These regulations are crucial in shaping construction practices and driving innovations in construction methods. For instance, various government agencies and industry bodies have established comprehensive safety standards and guidelines to reduce accidents and fatalities on construction sites [15,16]. These regulations often require construction companies to implement safety measures, provide training to workers, and regularly inspect construction sites to ensure compliance. Furthermore, environmental protection agencies enforce emissions standards to control and mitigate the release of pollutants into the air, including dust and other particulate matter generated during construction activities [17]. In response to these legal requirements, construction companies are continually seeking methods and technologies that not only enhance productivity and cost-efficiency but also align with safety and environmental regulations. Prefabricated structural systems, as one of the most innovative construction methods, have garnered attention for their potential to improve safety records and reduce environmental impact.

As previously indicated, studies in the past have compared the emissions produced during the construction phase and the environmental impacts of both the prefabricated systems and conventional systems [3,8,9,18,19,20]. Most of these studies focused on greenhouse gases (GHG) without considering other air emissions such as dust. During the construction process, dust is emitted from the energy used in the construction equipment [21]. It is important to quantify the dust emissions workers are exposed to from the production phase to the construction phase as various health damages, including cardiovascular disease, chronic obstructive pulmonary disease (COPD), and acute respiratory infection, are associated with dust [22,23]. However, studies to distinctly examine the health impacts of dust emissions on workers for both prefabricated systems and conventional systems from the production phase to the construction phase have not yet been conducted.

In terms of accidents, the construction industry accounts for more accidents compared to other industries because of its unique characteristics [24,25]. Although numerous measures have been taken to decrease fatalities and injuries on construction sites, the rate of accidents is still rising. With the introduction of prefabricated systems, previous studies have demonstrated that prefabricated construction can reduce accidents on construction sites [26,27,28]. According to a study by Li et al. [27], which developed a method to assess the quality and safety of prefabricated buildings, the safety is manageable and received a comprehensive score of 92.71. Additionally, Jeong and Jeong, [25] presented the risk ranking for work types using construction accident data. Work types associated with prefabricated construction had the lowest risk ranking [25]. However, there is a lack of research where the health impact on workers and accident risks are assessed to measure the excellence of prefabricated systems over conventional systems.

Against this backdrop, this study aims to analyze the health impacts of dust on workers and accident risks between prefabricated and conventional structural systems from the production phase to the construction phase. The specific objectives of our research are as follows:

• To quantitatively analyze dust emissions during the production, transportation, and construction phases of prefabricated and conventional structural systems.
• To assess the health impacts on workers exposed to dust during the production, transportation, and construction phases of both systems.
• To quantitatively analyze accident risks associated with the production, transportation, and construction phases of prefabricated and conventional structural systems.

The study will provide valuable insights into the health and safety implications of both construction systems. The findings of this study will have implications for the construction industry and contribute to the existing literature on the comparative analysis of dust health and accident risk impacts in prefabricated and conventional construction systems.

2. Literature Review

In accordance with the comparison between prefabricated systems and conventional systems in the construction industry, previous research was conducted as follows: (1) research related to environmental impact assessment between prefabricated systems and conventional systems, and (2) research related to safety analysis between prefabricated systems and conventional systems.

First, research was conducted to analyze the environmental impact between prefabricated systems and conventional systems [8,9,11,29]. For example, Tian and Spatari, [29] used life cycle assessment to assess the environmental impacts between prefabricated residential buildings and traditional methods. The results indicated that the prefabricated construction can reduce all environmental impacts except marine eutrophication [29]. Cao et al. [9] used life cycle assessment to compare the environmental impacts between a prefabricated residential building and a cast-in-situ residential building. Their research considered three damage categories (ecosystem damage, resource depletion, and health damage). The results found that the prefabricated building reduces the environmental impacts in terms of ecosystem damage (3.47%), resource depletion (35.82%), and health damage (6.61%) [9]. Mao et al. [8] developed a model to quantitatively analyze the GHG emissions between prefabrication construction and conventional construction from the manufacturing phase to the disposal phase. The results from this study concluded that GHG emissions per square meter can be reduced from 368 kg/m² to 336 kg/m² when applying prefabrication construction [8].

Second, previous studies were conducted in terms of safety analysis between prefabricated systems and conventional systems [26,27,30,31,32]. Wang et al. [30] assessed the safety risks in hoisting the construction of prefabricated components using the Human Factors Analysis and Classification System model (HFACS) and Bayesian Network (BN). The results showed that by improving factors such as construction conditions, the height of the tower crane, and unsafe supervision, accidents could be avoided during the hoisting of prefabricated buildings [30]. Fard et al. [31] analyzed the accidents and work-related injuries in modular or prefabricated building construction for both on-site construction and manufacturing plants. The results indicated that fractures and falls were the most frequent types of injury and accident, respectively, during modular construction [31]. Mohandes et al. [32] developed a Crane Safety Index (CSI) model to assess the health and safety of workers related to crane operations in modular integrated construction. When the developed CSI model was applied, safety factors that have an influence on crane operations were identified. Moreover, safety performance can be quantified with regard to crane operations in modular integrated construction [32].

3. Materials and Methods

As shown in Figure 1, the research decision-making process is shown. This study is conducted in four steps: (1) Collection of data (2) Calculation of dust emission (3) Health impact assessment (4) Calculation of the risk of accident.

Firstly, an industrial facility construction project was chosen to achieve our research objectives. This selection was based on the need to explore the impact of prefabrication construction in a real-world context. By studying an actual construction project, the study aimed to capture the practical implications and potential benefits of using prefabricated systems compared to conventional systems. To calculate dust emissions, established methodologies and emission factors specific to construction activities were utilized. These calculations were based on the quantity and type of materials used, construction methods employed, and operational parameters of both the prefabricated and conventional systems. For the health impact assessment, recognized frameworks and models that have been extensively used in previous studies were employed. Validated data and epidemiological studies were used to estimate the potential health risks associated with dust exposure. In the calculation of accident risk, historical accident data, supplemented by expert opinions and industry best practices, was used to estimate the accident risks associated with both construction systems.

3.1. Collection of Data

To analyze the health impacts of dust on workers and accident risk for both the prefabricated system and the conventional system from the manufacturing phase through the construction phase, appropriate data should be collected and established. The ‘M’ factory construction project is selected as a case study to assess the dust health impacts and accident risk. This project was originally designed with Steel Reinforced Concrete column (SRC) and steel girders, but due to a design change, the SRC and steel girders were replaced with Prefabricated Steel Reinforced Concrete column (PSRC) and Thin Steel-place Composite beam (TSC).

Table 1. Characteristics of the prefabricated system and conventional system used for ‘M’ factory construction.

Conventional System			Prefabricated System
SRC Column	Size (mm)	900 (W)	PSRC Column	Size (mm)	900 (W)
		900 (D)			900 (D)
	Height (m)	7		Height (m)	7
	Weight (ton)	2.22		Weight (ton)	1.3
Steel Girder	Size (mm)	918 × 303 × 19 × 37	TSC	Size (mm)	900 × 300 × 12 × 12 × 12
	Length (m)	9		Height (m)	9
	Weight (ton)	2.74		Weight (ton)	1.99

and Figure 2 show the characteristics of the prefabricated system (PSRC and TSC) and conventional system (SRC and steel girder) used for the ‘M’ factory construction project [6].

To calculate the health impacts of dust on workers for the prefabricated system and the conventional system, the following data were collected. First, during the manufacturing phase, the quantity of materials produced for use in the ‘M’ factory’s construction is collected from the bill of quantity, and the number of steel factory workers is collected from previous studies [33]. Second, during the construction phase, the construction working time, number of workers, and number of construction machines are collected from site observation for the prefabricated system and from previous research and expert interviews for the conventional system [3,6] (See

Table A1. Construction working time and resources for PSRC column.

PSRC Column	Working Time (Hour/Cycle)			Resource
	Min	Ave	Max
Lifting PSRC	0.08	0.18	0.4	Foreman 1 Rigger 2 Signalman 1 Tower crane 1
Unloading PSRC	0.13	0.15	0.55	Foreman 1 Steel worker 2 Rigger 1 Signalman 1 Tower crane1 Lift 1
Erecting PSRC	0.47	0.73	1.67	Steel worker 2
Welding Skin form	1.08	1.52	2.33	Welder 2
Painting Skin form	-	0.6	-	Painter 1
Pouring Concrete	0.5	0.87	1.33	Concrete worker 2 Pumpcar1
Sum	2.87	4.05	6.88

,

Table A2. Construction working time and resources for SRC column.

SRC Column	Working Time (Hour/Cycle)			Resource
	Min	Ave	Max
Wire to steel column	0.06	0.08	0.12	Flagman 1 Structural steel workers 3 Safety foreman 1 Tower crane
Lifting steel column	0.15	0.17	0.25	Flagman 1 Structural steel workers 3 Safety foreman 1 Tower crane
Erection steel column	0.37	0.42	0.62	Flagman 1 Structural steel workers 3 Safety foreman 1 Tower crane
Return tower crane	0.05	0.07	0.08	Tower crane
Delivery rebar	0.50	0.58	0.67	Laborers 2 Tower crane
Return tower crane	0.05	0.07	0.08	Tower crane
Assembly column rebar	3.00	3.25	3.50	Rodmen 3 Rechargeable scissor lift
Delivery form material	0.50	0.63	0.75	Laborers 2 Tower crane
Return tower crane	0.05	0.07	0.08	Tower crane
Column formwork	2.00	2.50	3.00	Carpenters 2 Laborer 1 Rechargeable scissor lift
Pouring concrete	0.50	0.87	1.33	Concrete workers 4 Pump car 1
Concrete curing	9.33	10.67	12.00
Column painting	0.87	1.03	1.07	Painter 1
Sum	17.43	20.39	23.55

and

Table A3. Construction working time and resources for TSC (Girder).

TSC (Girder)	Working Time (Hour/Cycle)			Resource
	Min	Ave	Max
Lifting TSC	0.13	0.28	0.43	Foreman 1 Rigger 3 Signalman 2 Steel worker 4 Tower crane 1 Lift 2
Adjusting TSC	0.13	0.37	0.77	Foreman 1 Rigger 3 Signalman 2 Steel worker 4 Tower crane 1 Lift 2
Erecting TSC	0.67	1	1.7	Steel worker 2 Lift 1
Painting TSC	0.27	0.43	0.53	Painter 2 Lift 2
Fireproofing TSC	0.37	0.47	0.83	Painter 3 Lift 1
Sum	1.57	2.55	4.27

).

To calculate the accident risk, the following data are collected. First, the probability of fatalities and injury rates for steel production factories and transport services are collected from the South Korean Ministry of Employment and Labor [24]. During the construction phase, the probability of fatality and injury rate related to construction work types are collected from previous studies [24,25].

Table 2. The probability of fatality and injury rate for steel factory and transport services.

	Year	Number of Workers	Injury	Fatality	Injury Rate (%)	Fatality per 10,000 Workers (‱)
Steel Factory	2018	941,907	9485	159	1.01	1.69
	2017	372,076	5079	95	1.37	2.55
	2016	315,054	4388	72	1.39	2.29
	2015	301,848	4583	72	1.52	2.39
	2014	283,500	4767	77	1.68	2.72
	2013	265,398	4934	64	1.86	2.41
Transport Services	2018	160,141	430	12	0.27	0.75
	2017	154,528	305	10	0.20	0.65
	2016	152,765	330	9	0.22	0.59
	2015	147,215	300	10	0.20	0.68
	2014	141,203	364	12	0.26	0.85
	2013	133,840	380	13	0.28	0.97

and

Table 3. The probability of fatality and injury rate for construction work types.

Work Type	Number of Workers	Injury	Fatality	Injury Rate (%)	Fatality per 10,000 Workers (‱)
Reinforced concrete works	1,553,610	1549	708	0.10	4.56
Painting works	190,486	83	219	0.04	11.5
Steel structure works	440,477	67	330	0.02	7.49

show the probability of fatalities and injury rates for steel production factories, transport services, and construction work types.

3.2. Calculation of Dust Emission

The dust emitted during the material manufacturing phase, transportation phase, and construction phase are all considered when estimating the dust emission for both the prefabricated system and the conventional system. During the manufacturing phase, dust is emitted from the manufacturing of section steel, forms, and deformed rebars. The dust emission from the material manufacturing phase is calculated by multiplying the quantity of material by the dust emission factors of the materials, as shown in Equation (1).

Table 4. Quantity of material and dust emission factors.

System	Materials	Quantity (kg)	Dust Emission Factor (kg-Dust/kg)
SRC	Rebar	32,921.6	1.14 × 10−4
	Steel Frame	84,559.4	14.98
Steel Girder	Steel	279,561	14.98
PSRC	Angle	39,930.6	1.14 × 10−4
	L-BAR	26,812.2	1.14 × 10−4
TSC	Steel	181,002.3	14.98

shows the quantity of materials and the dust emission factors provided in the LCI database available in the Republic of Korea [34].

$$M_i=Q_i\times {EF}_i$$

(1)

where M_i is the amount of dust emission from the material manufacturing phase for material i-th (kg), Q_i is the quantity of material i-th (kg), and EF_i is the dust emission factor of material i-th (kg-dust/kg).

During the transportation phase, dust is emitted from the combustion of the energy used by the transport vehicle from the manufacturing factory to the construction site [35]. Equation (2), suggested by Hong et al. [36] and Jeong et al. [3], is used to calculate the dust emission from transportation. In the Republic of Korea, the transportation distance from the factory to the construction site is set at 30 km in the development of the life cycle database [3]. Thus, this study used 30 km as the transportation distance. With regards to the transportation vehicles, a 25-ton trailer and a 20-ton truck were used. These vehicles use diesel as their energy source, and the dust emission factor of diesel is 7.2 × 10⁻⁵ kg/L [34].

Table 5. Load capacity and energy efficiency data for the vehicles.

Vehicle	Load Capacity (ton/ea)	Energy Efficiency (km/L)
25-ton trailer	25	2.5
20-ton truck	20	3.1

shows the load capacity and energy efficiency of the transportation vehicles [3].

$$T_i=2{\sum }_{j=1}(\frac{Q_i\times {TD}_{i,j}}{{LC}_{i,j}\times {EE}_{j,l}}\times {EF}_l)$$

(2)

where T_i is the amount of dust emission from the transportation of material i-th from the factory to the construction site (ton), Q_i is the quantity of material i-th (kg), TD_i,j is the transportation distance of vehicle j-th transporting material i-th (km), LC_i,j is the loading capacity of vehicle j-th for material i-th (ton/ea), EE_j,l is the energy efficiency of vehicle j-th which uses energy source l (km/L), and EF_l is the dust emission factor of energy source l (kg/L).

During the construction phase, dust is emitted from the energy used by the construction equipment [21]. To calculate the dust emission during the construction process, first, the dust emission data of construction equipment during operation and idle times should be established. During the equipment operation, the dust emission data are calculated by multiplying the energy consumption of the equipment by the dust emission of the energy used by the equipment (i.e., electricity and diesel). Jeong et al. [3] set the energy consumption of equipment idling at 17.8% of the energy consumption of the operating equipment. Therefore, during the idle time of the equipment, the dust emission data are calculated by multiplying 17.8% of the energy consumption of the operating equipment by the dust emission factor of the energy used by the equipment. This study used the dust emission factor of electricity 1.08 × 10⁻⁴ kg/kWh [34].

Table 6. Energy consumption and dust emission data for construction equipment.

Equipment	Energy Consumption (kW/h)		Dust Emission Data (kg/hr)
	Operation	Idle	Operating	Idle
12-ton Tower Crane	94.1	16.7498	1.02 × 10−2	1.81 × 10−3
Lift	10.8	1.9224	1.17 × 10−3	2.08 × 10−4
Concrete pump car	31 *	2.27 *	2.23 × 10−3	1.64 × 10−4

* The unit is L/h.

shows the energy consumption and dust emission data for the construction equipment [3,37].

Second, the working time and idle time of the construction equipment should be calculated. This study used the discrete event simulation known as STate and ResOurse Based Simulation of COnstruction ProcEsses (STROBOSCOPE) to calculate the working time and idle time of the construction equipment [38]. STROBOSCOPE captures all the complexity during the construction process, including resource inputs and weather conditions [4,39]. The iteration is set to 1000 in order to address the uncertainty in the working time and idle time of the construction equipment. Therefore, the working time and idle time are used to calculate the dust emitted during the construction phase by multiplying them by the dust emission data in Table 6.

3.3. Health Impact Assessment

The health impact assessment is conducted in the following three steps: (i) classification, (ii) characterization, and (iii) Economic cost of health impacts [40].

3.3.1. Classification

The health impact of dust is classified into three categories: COPD, acute respiratory infections, and pneumoconiosis [21]. These health damages are lung diseases caused by inhaling dust over a long period of time.

3.3.2. Characterization

The characterization has three phases, from fate analysis to damage analysis. The detailed explanation is as follows.

Fate Analysis: Dust emissions from the material manufacturing phase, transportation phase, and construction phase of the prefabricated system and the conventional system are converted into added concentrations of dust (Equation (3)).

$$C_i=F\times E_i$$

(3)

where C_i is the added concentration of dust for each phase i-th (µg/m³), F is the fate factor (m⁻³), which is calculated as 4.17 × 10⁻¹⁵ m⁻³ by dividing the PM₁₀ emissions (10,533 tons) by the concentration level (44 µg/m³) in the Republic of Korea [41], and E_i is the dust emission for each phase i-th (µg).

Effect Analysis: Equations (4) and (5) are used to calculate the health effects of dust emissions on workers from the material manufacturing phase to the construction phase of the prefabricated system and the conventional system.

Table 7. Effect factors (UR) for health damage.

Type of Health Damage	UR Value (Cases/(μg·m−3))
COPD	6.00 × 10−7
Acute respiratory infections	6.30 × 10−3
Pneumoconiosis	7.70 × 10−7

shows the effect factor values for the health damages [40].

$${HD}_i=N\times \frac{{UR}_i}{L}$$

(4)

$$T_i={HD}_i\times C_i$$

(5)

where HD_i is the added cases of health damage i-th caused by dust increase per unit concentration (cases/(µg·m⁻³ a)), N is the number of workers, UR_i is the effect factor (cases/µg·m⁻³), L is the average lifetime of workers (a), which is 78.6 years for South Koreans [42], and T_i is the added number of workers with health damage i-th caused by dust (cases/a).

Damage Analysis: Equations (6)–(8) are used to calculate the disability-adjusted life year, which evaluates the relationship between the dust concentration and health damage.

Table 8. Duration and disability weights for health damage.

Type of Health Damage	Li (a)	DW
COPD	20	0.15
Acute respiratory infections	0.004	0.03
Pneumoconiosis	15	0.26

shows the duration and disability weights for the health damages [40].

$${DALY}_i={YLL}_i+{YLD}_i$$

(6)

$${YLD}_i=L_i\times {DW}_i$$

(7)

$$U_i=T_i\times {DALY}_i$$

(8)

where DALY_i is the disability-adjusted life years of health damage case i-th (a/case), YLL_i is the years of life lost to health damage case i-th (a/case), YLD_i is the years of life with disability from health damage case i-th (a/case), L_i is the duration of health damage case i-th (a), DW_i is the disability weight of health damage case i-th, and U_i is the added number of DALY of a worker with health damage i-th caused by dust (a).

3.3.3. Economic Cost of Health Impacts

In this study, Equations (9)–(11) are used to convert the health damages to a cost, i.e., willingness to pay (WTP). The value of a statistical life (VSL) for the target country (the Republic of Korea) is based on the gross national income per capita of the Republic of Korea ($34,980) and the United States, which is the base country ($70,430) in 2021 [43]. The US Environmental Protection Agency (EPA) has set the value of a statistical life and elasticity factor at $7.4 million and 0.7, respectively [44]. This study assumed the average age of workers to be 45 years.

$${VSL}_{target}={VSL}_{base}\times ({{GNIpercapita}_{target}/{GNIpercapita}_{base})}^{elasticity}$$

(9)

$${VSLY}_{target}=\frac{{VSL}_{target}\times r}{1-({1+r)}^{-y}}$$

(10)

$$WTP=U_i\times {VSLY}_{target}$$

(11)

where VSL_target is the value of a statistical life for the target country ($), VSL_base is the value of a statistical life for the reference country ($), GNI per capita_target is the gross national income per capita of the target country ($), GNI per capita_base is the gross national income of the reference country ($), elasticity is the income elasticity factor, VSLY_target is the value of a statistical life year of the target country ($), r is the discount rate (4%) [45], y is the remaining years of the life of workers (a), and WTP is the willingness to pay ($).

3.4. Calculation of Accident Risk

In this study, the risk of accident, including the rate of fatality and the rate of injury is calculated during the material manufacturing phase, transportation phase, and construction phase based on man·day. Man·day refers to the number of days needed for one worker to finish a task [46]. The following equations are used to calculate the risk of an accident (Equations (12) and (13)).

$${Estimatednumberoffatality}_i=\sum ({Probabilityoffatality}_i\times {Man·day}_i)$$

(12)

$${Estimatednumberofinjury}_i=\sum ({Probabilityofinjury}_i\times {Man·day}_i)$$

(13)

As mentioned in Section 3.1, the probability of fatalities and injury rates were collected for the material manufacturing phase, transportation phase, and construction phase. During the material manufacturing phase, the man·day for factory workers was set at 1.2 ton/man·day for normal steel production and 0.8 ton/man·day for PSRC members’ production by interviewing steel factory managers. The man·day is calculated for the transportation phase based on the number of drivers and the working day. The working day is calculated by considering the transportation distance from the plant to the construction site (30 km) and the speed limit of the vehicles (80 km/h). For the construction phase, as mentioned in Section 3.2, the STROBOSCOPE simulation can also calculate the man·day based on the input of the construction workers.

4. Results

4.1. Results of Dust Emission for the Prefabricated System and the Conventional System

The results of the dust emission during the material manufacturing phase, transportation phase, and construction phase for the prefabricated system and the conventional system are shown in

Table 9. Results of the dust emission during the materials manufacturing phase for the structural systems.

Structural System		Materials	Dust Emission (kg)
Conventional System	SRC	Rebar	3.75
		Steel Frame	1,266,699.81
	Steel Girder	Steel	4,187,823.78
Prefabricated System	PSRC	Angle	5.51
		L-BAR	3.70
	TSC	Steel	2,711,414.45

,

Table 10. Results of the dust emission during the transportation phase for the structural systems.

Structural System		Materials	Dust Emission (kg)
Conventional System	SRC	Rebar	2.29 × 10−3
		Steel Frame	5.85 × 10−3
	Steel Girder	Steel	1.93 × 10−2
Prefabricated System	PSRC	Angle	2.76 × 10−3
		L-BAR	1.85 × 10−3
	TSC	Steel	1.25 × 10−2

and

Table 11. Results of the dust emission during the construction phase for the structural systems.

Structural System		Emission (kg/Cycle)
SRC	Wire to steel column	8.86 × 10−4
	Lifting steel column	1.93 × 10−3
	Erection steel column	4.79 × 10−3
	Return tower crane	6.80 × 10−4
	Delivery rebar	5.94 × 10−3
	Return tower crane	6.79 × 10−4
	Assembly column rebar	3.80 × 10−3
	Delivery form material	6.38 × 10−3
	Return tower crane	6.81 × 10−4
	Column formwork	2.92 × 10−3
	Pouring concrete	2.02 × 10−3
	Column painting	1.16 × 10−3
	Lift waiting	2.00 × 10−4
	Crane waiting	4.30 × 10−3
	Pump car waiting	1.17 × 10−3
PSRC	Lifting PSRC	2.23 × 10−3
	Unloading PSRC	3.19 × 10−3
	Erecting PSRC	9.72 × 10−3
	Welding skin form	1.93 × 10−3
	Painting skin form	7.11 × 10−4
	Pouring concrete	2.00 × 10−3
	Lift waiting	6.29 × 10−5
	Crane waiting	4.83 × 10−4
	Pump car waiting	3.03 × 10−4
TSC/Steel Girder	Lifting TSC (Steel girder)	2.85 × 10−3
	Adjusting TSC (Steel girder)	4.77 × 10−3
	Erecting TSC (Steel girder)	1.27 × 10−2
	Painting TSC (Steel girder)	4.79 × 10−4
	Fireproofing TSC (Steel girder)	6.53 × 10−4
	Lift 1 waiting (Steel girder)	6.89 × 10−5
	Lift 2 waiting (Steel girder)	1.63 × 10−5
	Crane waiting (Steel girder)	1.67 × 10−3

and Figure 3. The results showed that the conventional system and the prefabricated system produced 5,454,527.43 kg of dust and 2,711,423.72 kg of dust, respectively, during the entire life cycle. During the material manufacturing phase, the conventional system produced 5,454,527.34 kg of dust, and the prefabricated system produced 2,711,423.66 kg of dust. For both the conventional and prefabricated systems, the steel girder and the TSC accounted for most of the dust emission, i.e., 4,187,823.78 kg and 2,711,414.45 kg of dust, respectively.

In the case of the transportation phase, 2.75 × 10⁻² kg and 1.71 × 10⁻² kg of dust were emitted during the transportation of the conventional system and the prefabricated system, respectively.

During the construction phase, the conventional system produced 6.08 × 10⁻² kg of dust and the prefabricated system produced 4.39 × 10⁻² kg of dust. Since the steel girder and the TSC had the same work process and working time, the dust emission was the same. Therefore, when the prefabricated system is applied instead of the conventional system, the dust emission can be decreased by 50.29%, 37.64%, and 27.83% during the material manufacturing phase, transportation phase, and construction phase, respectively.

4.2. Results of the Health Impact Assessment for the Prefabricated System and the Conventional System

As shown in

Table 12. Results of the health impact during the materials manufacturing phase for the structural systems.

Structural System		U (a)			WTP ($)
		COPD	Acute Respiratory Infections	Pneumoconiosis	COPD	Acute Respiratory Infections	Pneumoconiosis
Conventional System	SRC	3.61 × 10−3	3.25 × 10−4	7.90 × 10−3	8.95 × 102	8.04 × 101	1.96 × 103
	Steel Girder	1.19 × 10−2	1.07 × 10−3	2.60 × 10−2	2.96 × 103	2.66 × 102	6.47 × 103
Prefabricated System	PSRC	2.62 × 10−8	2.36 × 10−9	5.74 × 10−8	6.50 × 10−3	5.84 × 10−4	1.42 × 10−2
	TSC	7.73 × 10−3	6.95 × 10−4	1.70 × 10−2	1.92 × 103	1.72 × 102	4.19 × 103

,

Table 13. Results of the health impact during the transportation phase for the structural systems.

Structural System		U (a)			WTP ($)
		COPD	Acute Respiratory Infections	Pneumoconiosis	COPD	Acute Respiratory Infections	Pneumoconiosis
Conventional System	SRC	7.27 × 10−15	6.53 × 10−16	1.59 × 10−14	1.80 × 10−9	1.62 × 10−10	3.94 × 10−9
	Steel Girder	1.73 × 10−14	1.55 × 10−15	3.77 × 10−14	4.27 × 10−9	3.84 × 10−10	9.35 × 10−9
Prefabricated System	PSRC	4.12 × 10−15	3.70 × 10−16	9.01 × 10−15	1.02 × 10−9	9.17 × 10−11	2.23 × 10−9
	TSC	1.12 × 10−14	1.00 × 10−15	2.44 × 10−14	2.77 × 10−9	2.49 × 10−10	6.05 × 10−9

and

Table 14. Results of the health impact during the construction phase for the structural systems.

Structural System		U (a)			WTP ($)
		COPD	Acute Respiratory Infections	Pneumoconiosis	COPD	Acute Respiratory Infections	Pneumoconiosis
Conventional System	SRC	9.26 × 10−14	8.32 × 10−15	2.03 × 10−13	2.29 × 10−8	2.06 × 10−9	5.02 × 10−8
	Steel Girder	6.00 × 10−14	5.39 × 10−15	1.31 × 10−13	1.49 × 10−8	1.34 × 10−9	3.25 × 10−8
Prefabricated System	PSRC	2.96 × 10−14	2.66 × 10−15	6.49 × 10−14	7.34 × 10−9	6.60 × 10−10	1.61 × 10−8
	TSC	6.00 × 10−14	5.39 × 10−15	1.31 × 10−13	1.49 × 10−8	1.34 × 10−9	3.25 × 10−8

and Figure 4, the results of the health impact of dust on workers during the material manufacturing phase, transportation phase, and construction phase for conventional and prefabricated systems are shown. The results showed that the conventional system and the prefabricated system had a willingness to pay $12,631.40 and $6282.02, respectively, during the entire life cycle. During the material manufacturing phase, the added number of workers with COPD, acute respiratory infections, and pneumoconiosis for the conventional system was 1.55 × 10⁻² a, 1.40 × 10⁻³ a, and 3.39 × 10⁻² a, respectively, with a willingness to pay $3.86 × 10³, $3.46 × 10², and $8.43 × 10³, respectively. For the prefabricated system, the added number of workers with COPD, acute respiratory infections, and pneumoconiosis was 7.73 × 10⁻³ a, 6.95 × 10⁻⁴ a, and 1.70 × 10⁻² a respectively with a willingness to pay $1.92 × 10³, $1.72 × 10² and $4.19 × 10³, respectively.

During the transportation phase, for the conventional system, the added number of workers with COPD, acute respiratory infections, and pneumoconiosis was 2.46 × 10⁻¹⁴ a, 2.20 × 10⁻¹⁵ a, and 5.36 × 10⁻¹⁴ a, respectively, with a willingness to pay $6.07 × 10⁻⁹, $5.46 × 10⁻¹⁰, and $1.33 × 10⁻⁸, respectively. On the other hand, the added number of workers with COPD, acute respiratory infections, and pneumoconiosis for the prefabricated system was 1.53 × 10⁻¹⁴ a, 1.37 × 10⁻¹⁵ a, and 3.34 × 10⁻¹⁴ a, respectively, with a willingness to pay $3.79 × 10⁻⁹, $3.41 × 10⁻¹⁰ and $8.28 × 10⁻⁹, respectively.

During the construction phase, the added number of workers with COPD, acute respiratory infections, and pneumoconiosis for the conventional system was 1.53 × 10⁻¹³ a, 1.37 × 10⁻¹⁴ a, and 3.34 × 10⁻¹³ a, respectively, with a willingness to pay $3.78 × 10⁻⁸, $3.40 × 10⁻⁹, and $8.27 × 10⁻⁸, respectively. For the prefabricated system, the added number of workers with COPD, acute respiratory infections, and pneumoconiosis was 8.96 × 10⁻¹⁴ a, 8.05 × 10⁻¹⁵ a, and 1.96 × 10⁻¹³ a, respectively, with a willingness to pay $2.22 × 10⁻⁸, $2.00 × 10⁻⁹, and $4.86 × 10⁻⁸, respectively. Thus, when the prefabricated system is applied instead of the conventional system, the health impact on workers can be decreased by 50.27%, 37.65%, and 41.21%, respectively, during the material manufacturing phase, transportation phase, and construction phase.

4.3. Results of the Accident Risk for the Prefabricated System and the Conventional System

The results of the accident risk, including the injury risk and the fatality risk, for the prefabricated and conventional systems are shown in

Table 15. Results of the accident risk for the structural systems.

Structural System	Accident Risk	Material Manufacturing Phase	Transportation Phase	Construction Phase
SRC	Injury Risk	1.44 × 102	6.75 × 10−2	2.94 × 10−1
	Fatality Risk	2.29 × 102	2.11 × 10−1	1.88 × 101
Steel Girder	Injury Risk	3.43 × 102	2.25 × 10−2	3.14 × 10−2
	Fatality Risk	5.46 × 102	7.03 × 10−2	1.14 × 101
PSRC	Injury Risk	1.23 × 102	4.50 × 10−2	4.42 × 10−2
	Fatality Risk	1.95 × 102	1.41 × 10−1	8.88 × 100
TSC	Injury Risk	2.22 × 102	2.25 × 10−2	3.14 × 10−2
	Fatality Risk	3.53 × 102	7.03 × 10−2	1.14 × 101

and Figure 5. The injury risk and the fatality risk represent the estimated number of injuries and fatalities that can occur during the material manufacturing phase, transportation phase, and construction phase of the prefabricated system and the conventional system. The injury and fatality risks for the entire life cycle of the conventional system and the prefabricated system were 4.87 × 10² injuries and 8.05 × 10² fatalities, respectively, and 3.45 × 10² injuries and 5.69 × 10² fatalities, respectively. Regarding the material manufacturing phase, the accident risk was 4.87 × 10² injuries and 7.75 × 10² fatalities, and 3.45 × 10² injuries and 5.49 × 10² fatalities for the conventional system and the prefabricated system, respectively. During the transportation phase, the accident risk was 9.00 × 10⁻² injuries and 2.81 × 10⁻¹ fatalities, and 6.75 × 10⁻² injuries and 2.11 × 10⁻¹ fatalities for the conventional system and the prefabricated system, respectively. With regard to the construction phase, the accident risk was 3.26 × 10⁻¹ injuries and 3.02 × 10¹ fatalities, and 7.56 × 10⁻² injuries and 2.03 × 10¹ fatalities for the conventional system and the prefabricated system, respectively. Therefore, when the prefabricated system is applied instead of the conventional system, the accident risk can be decreased by 29.20%, 25.00%, and 76.80% for injuries, and 29.20%, 25.00%, and 32.89% for fatalities during the material manufacturing phase, transportation phase, and the construction phase, respectively.

5. Discussion

With regards to evaluating the superiority of prefabricated systems over conventional systems, the previous studies have the following limitations. First, previous researchers only considered greenhouse gases (GHG) in assessing the environmental and health impacts. Second, most of the previous studies used a qualitative method to analyze risk during the construction phase. Therefore, this study recommends the following additional methods to overcome the limitations of previous studies. First, this study will analyze the health impacts of dust on workers between prefabricated and conventional structural systems from the production phase to the construction phase. Second, quantitatively analyze the risk of fatality and injury between prefabricated and conventional structural systems from the production phase to the construction phase.

Previous studies have tried to prove the excellence of prefabricated systems over conventional systems in terms of productivity, environmental impacts, cost, etc., but this study proved the excellence of prefabricated in terms of dust health impacts and accident risk. First, this study quantitatively assessed the health impact of dust on workers using a factory construction project as a case study. Second, accident risk is assessed quantitatively by using data collected in the Republic of Korea on the probability of fatalities and injury rates. Moreover, this study considered the material manufacturing phase, transportation phase, and construction phase to prove the excellence of the prefabricated system over the conventional system. When these phases are considered, they help in decision-making during the preconstruction stage of the construction project. The operation phase and demolition phase are not considered because of uncertainties in estimating the dust emissions produced during the 50-year lifespan of the building. Furthermore, for the demolition phase, it is difficult to quantify the dust emissions due to the lack of data.

As shown in the results, when the prefabricated system is applied instead of the conventional system, the dust emission, health impacts, and accident risk can be reduced. Compared to the previous research results, some research explained that the prefabricated system is more eco-friendly than the conventional system [8,9,11]. This study aligns with these findings, further confirming that the prefabricated system is indeed more eco-friendly than the conventional system in terms of dust emissions and health impacts. The findings of this study indicate that prefabricated construction systems have lower dust emissions compared to conventional construction systems, but there is still a need to implement measures to reduce dust exposure in these systems. This may include the use of dust suppression methods and the implementation of effective ventilation systems.

The results of this study have the following practical applications. In terms of dust health impacts, it can provide decision-makers, such as construction project managers, policymakers, and health and safety professionals, with insights into the potential benefits of using prefabricated systems compared to conventional systems. Recently, dust emission was considered one of the suspensions of work criteria at a construction site in the Republic of Korea [17]. However, until now, the data on dust emissions could only be collected as daily national data from the Korea Metrological Administration. So, the results of this study can be utilized to predict dust emissions at pre-construction phases. It is very helpful to decision-makers. In addition, it will help insurance companies to evaluate the risk of an event related to dust health impacts, reducing their liability risk. In terms of accident risks, it can inform the development of risk management protocols to minimize the risk of accidents during prefabrication and on-site assembly. Additionally, it can inform the development of training and education programs for workers to minimize the risk of accidents in factories and construction sites. As shown in Figure 6, the material manufacturing phase accounts for more than 90% of the dust health impact and accident risk for the prefabricated system, so insurance companies can focus more on that phase. Regardless, the construction phase should be carefully considered when generating policies and regulations in terms of insurance for the prefabricated system. The findings of this study contribute to the existing literature and provide useful information for the construction industry to enhance the health and safety of workers in construction sites.

This study has the following limitations. First, this study only considered steel products to calculate the dust health impacts and the accident risk during the material manufacturing phase. Second, it is challenging to generalize the results of this study because the prefabrication construction methods used can vary based on the project, construction practices, and regulations in different countries or regions. Third, this study only focused on the dust emission and accident risk between the conventional and prefabricated systems to select the better system in terms of macro-aspects. So, this study did not consider several detailed factors such as dust types, environmental conditions, dust handling, and control practices. Lastly, this study selected only one construction project as a case study to achieve its objectives due to the lack of case studies about prefabricated structural systems in the Republic of Korea. So, it is very hard to collect real data.

6. Conclusions

This study analyzed the superiority of the prefabricated system over the conventional system in terms of dust health impacts and accident risk during the material manufacturing phase, the transportation phase, and the construction phase.

The research was conducted in the following four steps: (1) Collection of data, (2) Calculation of dust emission, (3) Health impact assessment, and (4) Calculation of accident risk.

The results of this study can be summarized as follows. First, for the entire life cycle, the conventional system and the prefabricated system produced 5,454,527.43 kg of dust and 2,711,423.72 kg of dust, respectively. When the prefabricated system is used in place of the conventional system, the dust emission can be reduced by 50.29%, 37.64%, and 27.83% during the material manufacturing phase, the transportation phase, and the construction phase, respectively. Second, in terms of the health impacts, the conventional system and the prefabricated system had a willingness to pay $12,631.40 and $6282.02, respectively, during the entire life cycle. When the prefabricated system is applied instead of the conventional system, it can be decreased by 50.27%, 37.65%, and 41.21% during the material manufacturing phase, the transportation phase, and the construction phase, respectively. Third, the injury and fatality risks for the entire life cycle of the conventional system and the prefabricated system were 4.87 × 10² injuries and 8.05 × 10² fatalities, respectively, and 3.45 × 10² injuries and 5.69 × 10² fatalities, respectively. The accident risk can be decreased by 29.20%, 25.00%, and 76.80% for injuries and by 29.20%, 25.00%, and 32.89% for fatalities during the material manufacturing phase, transportation phase, and construction phase, respectively, when the prefabricated system is applied.

This study has the following contributions. First, this study assessed the health impacts of dust emissions on workers for the prefabricated system and the conventional system. As previous studies have focused on productivity, cost, and environmental impacts to compare both systems, this study contributes to the body of literature by focusing on dust health impacts in proving the superiority of prefabricated systems. Second, this study quantitatively evaluated the accident risk in terms of fatalities and injuries during the material manufacturing phase, transportation phase, and construction phase for the prefabricated system and the conventional system, unlike some previous studies that assessed risk qualitatively.

Further research will conduct a multi-criteria decision analysis to help decision-makers choose the optimal structural system in terms of dust health impact and accident risk. Second, further research will investigate the factors that influence implementing safety measures during prefabrication construction and the impacts of these measures on reducing the accident risk. Third, further research will include multiple prefabricated facilities to enhance the comparability of data and broaden the generalizability of the findings. Lastly, future studies could explore the integration of digital twin technology in construction processes to simulate and optimize dust emissions and safety measures. Digital twins can provide a virtual environment for testing various scenarios and identifying strategies for reducing dust emissions and accidents.