Introduction/Issue

The protection of employees primarily relies on risk assessment and the establishment of an appropriate prevention policy (Mohammed-Brahim B., Avril 2009). Regarding chemical risks, the assessment process is often challenging due to the diversity of products and preparations used and the lack of knowledge about their hazards. (Métallurgie en poche)

In Algeria, Executive Decree No. 05-08, dated January 8, 2005, defines specific safety requirements for hazardous substances to ensure that workers are provided with preventive measures against occupational risks in the workplace (Roland Iosif Moraru, 2022). This decree specifies labeling and storage procedures, as well as the employer’s obligation to provide a safety data sheet. In Europe, the obligation to assess risks originates from European Directive No. 89/391/EEC dated June 12, 1989, which outlines fundamental principles for the prevention of occupational risks and the protection of workers’ safety and health (Mohamed Nour Azzougagh, 14 May 2021). Following the issuance of this directive, the general obligation for risk assessment was further elaborated into specific obligations for risk assessment, either corresponding to a type of hazard or a type of activity where the employer is required to ensure the safety and health of workers in all aspects related to their work (Antara Das a, 2023).

The field of metallurgy is one of the sectors most exposed to chemical risks, particularly in steel mills, which are highly hazardous due to significant emissions of dust from external scrap metal stocks, additives, and primarily heavy metals, fumes from molten steel, refractory products, solvents, and those occurring at various stages of production, impacting the health of workers and the environment. (Niepsuj G. et al., 1993)

Medical surveillance of workers exposed to chemical risks highlights the emergence of numerous complaints and health issues, such as respiratory, ocular, and cutaneous symptoms (Jose Carlos Mora Barrantes, 2023). Following this observation, a study was conducted on chemical risk in a large steel mill workshop located within the largest steel production facility of its kind in Africa, in the city of Oran (Elena Stefana a b, 2023).

The objectives of this study are to assess chemical risk in a steel mill using the method of the National Research and Safety Institute (INRS) and to describe the health problems reported among the workers in this steel mill (Toma, 2023).

1. Materials and methods

1.1. Understanding of the Company

• Site Visits: The workplace site visits aim to research and identify the workstations with chemical risks through direct observation of various production stages, interviews with workers, consultation of company documents, and the study of the production process.

• Study of Workstations with Chemical Risks: Workstations with chemical risks are identified through direct observation of tasks and interviews with workers. These workstation studies have allowed us to compile and catalog the various chemical products being handled and their conditions of use.

1.2. Study Population

This study includes all the workers in a steel mill, a metallurgical company located in the Oran region.

• Chemical Risk Assessment: According to the INRS Method (2005): The assessment of chemical risk using the INRS method is based on an objective evaluation approach, which helps establish prevention action priorities. It primarily relies on the quality of information provided in the safety data sheet. This method enables the prioritization of potential risks, including the evaluation of risks through inhalation and skin contact.

• Method Limitations: The method’s effectiveness depends on the quality of labeling and safety data sheets. It does not allow for the assessment of chronic exposure through ingestion. This approach does not address the evaluation of risks related to accidental events, which are estimated using a more complex probabilistic approach. Additionally, storage conditions are not evaluated within this method.

• Identification of Workstations with Chemical Risks: The level and degree of exposure to chemical products vary from one workshop to another for the same chemical-related positions. For instance, consider positions 5 and 8 as examples.

2. Results

In total, 374 male workers at the steel mill participated in our study. Approximately 68% of them are aged between 30 and 50 years. Around 46% are smokers, and nearly all are non-drinkers (99.2%).

The mechanical workshop (maintenance) has the largest number of workers, accounting for 21.7% of the workforce. The positions of “assistant foreman” and “foreman” are the most commonly occupied by workers, with 21.7% and 12.6% respectively.

The most commonly represented professional background exposing to chemical risk is that of a mechanic (16%), followed by a welder (14.7%). More than 34% of workers have 5 years of seniority. Their tenure at the workstation ranges from 3 to 6 years, with an average of 4.7 ± 1 years.

2.1. Identification of Workstations with Chemical Risks

The level and degree of exposure to chemical products vary from one workshop to another for the same chemical-related positions. For instance, consider positions 5 and 8 as examples.

Figure 01. Identifying workstations in relation to the production process

2.2. Identification of Chemical Products

Many chemical products are used in steel mills, including metals.

Figure 02. Chemical products identified in the production process.

2.3. Chemical Risk: assessment (according to the simplified method of chemical risk assessment by INRS 2005)

• Involves evaluating the risk for all Homogeneous Exposure Groups (HEGs) in a work area characterized by a significant overall potential risk (geographical concept).

• Following the workplace inspection at the steel mill, 5 Homogeneous Exposure Groups (HEGs) have been selected based on chemical risk exposure.

• Work Unit Approach:

1. Electric Arc Furnace (EAF)

2. Ladle Furnace (LF)

3. Continuous Casting Machine (CCM)

4. Refractory Workshop

5. Mechanical Maintenance Workshop

• Electric Arc Furnace Unit: Only lime is assigned a class 4, and carbon is classified as class 3. Carbon and lime have a likely very high HRP (Hazard Rating Potential) score, indicating a high priority. All products used in the electric arc furnace have a high volatility score. Lime has a likely very high inhalation risk score, while carbon has a moderate risk. Both lime and carbon have a likely very high risk score for skin contact.

Table 1: Chemical Risk Rating in the Electric Arc Furnace Unit

• Ladle Furnace (LF) Unit: Ferrosilicon, Ferrovanadium, and carbon are classified as hazard class 3. Ferromanganese and fluorite are class 2, while aluminum, nitrogen, and argon are class 1.

• Chemical Quantity Class in LF: To determine the quantities of chemicals used (tonnes/day), we multiplied the amount used per ladle by the number of ladles per shift (9 ladles on average). The temporal reference is the amount consumed per day (shift). The most consumed chemical in LF is carbon (20.7 tonnes). Carbon poses a significant risk that requires a high priority for action.

• Determination of Frequency of Use Classes: It was assumed that exposure occurs whenever a chemical product is used at the studied workstation. To obtain the frequency of use for each product, the total melting time (35 minutes) was calculated and then multiplied by the number of ladles (9 ladles) per day (8-hour shift): 35 minutes X 9 = 315 minutes (5 hours and 25 minutes). Ferrovanadium and carbon have a moderate inhalation risk, requiring a moderate priority. Ferrosilicon, ferrovanadium, and carbon have a likely very high risk for skin contact. Ferromanganese and fluorite have a moderate skin contact risk.

Table 2: Chemical Risk Assessment in the Ladle Furnace (LF) Unit

• Liquid Steel: Four chemical elements have been classified as class 4 (P, Ni, As, Pb), and six chemical elements have been classified as class 3 (C, Cr, V, Co, B, Ce) based on the risk phrases. None of the components have a high HRP (Hazard Rating Potential) score, but eleven of them have a moderate score, requiring a medium priority for action, namely (C, P, Cr, Ni, V, As, Pb, Co, B, Ce, Fe).
  Most of the components in liquid steel have a high volatility score. Four components have a likely very high inhalation risk score (P, Ni, As, Pb), while two components (Cr, Co) have a moderate risk score. Regarding skin risk, ten components (C, P, Cr, Ni, V, As, Pb, Co, B, Ce) have a likely very high score, while four components (S, Cu, Sn, Sb) have a moderate risk.

Table 3: Chemical Risk Assessment for Liquid Steel

• Continuous Casting Machine (CCM) Unit: The same components found in liquid steel are present in the Continuous Casting Machine unit. The scores for the CCM unit are similar to those of liquid steel.

• Refractory Unit: Unshaped Product B80:

1. Application: steel ladle: The predominant component is alumina. Na2O, K2O, and CaO are classified as class while Al2O3 and Fe2O3 are class 2.
   Lime has a likely very high HRP (Hazard Rating Potential) score. All components have a moderate volatility score. Lime and the mixture of potassium oxide and sodium oxide have a likely very high inhalation risk score. The components of Product B80 have the same skin and inhalation risk score.

2. Spray EAF (Gunning Mix): Application: EAF spraying material. Magnesium oxide is the major component. Only lime is classified as class 4, while magnesium oxide and silica have a moderate HRP (Hazard Rating Potential) score. Lime has a likely very high inhalation risk score. The components have the same risk for skin contact and inhalation.

3. Spray Tundish: Application: used as a working lining for the distributor.
   It mainly contains magnesium oxide. The NaO2 + K2O mixture is classified as class 4. Nearly all components have a moderate HRP (Hazard Rating Potential) score except for iron oxide. All components have a moderate volatility score, and the NaO2 + K2O mixture has a likely very high inhalation risk score. The risk for skin contact and inhalation is similar.

Table 4: Chemical Risk Assessment in the Refractory Unit

• Machine Maintenance Unit:

1. Inventory of the most commonly used refractory products: Synthetic solvent based on aromatic hydrocarbons. Polyethylene polyphenyl isocyanate is classified as class 3. Aromatic hydrocarbons and polyethylene polyphenyl isocyanate all have a likely very high HRP (Hazard Rating Potential) score. The inhalation risk score is likely very high for aromatic hydrocarbons and moderate for polyurethane. The skin contact risk score is moderate for both maintenance products.

Table 5: Chemical Risk Assessment in the Machine Maintenance Unit

1. Summary of Potential Risks by Unit:

The Electric Arc Furnace unit has the highest potential risk.

Table 6: Distribution of Potential Risks by Unit

1. Summary of Risks by Inhalation and Skin Contact (by Unit):

The Refractory unit has the highest inhalation risk, while the Continuous Casting Machine unit has the highest skin contact risk.

Table 7: Inhalation and Skin Contact Risk

3. Discussion

Simplified Chemical Risk Assessment According to the INRS Method: (Vincent R., 2005)

Our study was conducted in a steel mill that employs 374 workers, in a steel industry company with nearly 6000 employees, with which our service has a partnership.

During the phase of potential risk prioritization, several chemical products or agents had multiple risk statements. When multiple risk statements are present, we considered the one with the highest hazard class (according to the INRS method).

In the Electric Arc Furnace unit, both lime (calcium oxide) and carbon had a potentially very high Hazard Rating Points (HRP) score. The inhalation risk score was very high for lime and moderate for carbon, along with a very high skin contact risk score for these same substances. In the Ladle Furnace unit, for the prioritization of potential risks, only carbon had a potentially very high risk. Three chemical agents, namely ferrosilicon, ferrovanadium, and carbon, had a potentially very high skin contact risk, requiring immediate corrective measures.

It’s worth noting that carbon had a high HRP score, a very high skin contact risk score, and a moderate inhalation risk score, despite the absence of a risk statement. This can be explained by the fact that it is classified based on its Very Low Exposure Limit (VLEP) of 2 mg/m³, as stated in the safety data sheet, and due to its significant quantity used. (Servet et al, 2013)

In the Continuous Casting Machine unit, no chemical element had a very high HRP score. However, four chemical elements had a very high inhalation risk score (P, Ni, As, Pb), and ten components (C, P, Cr, Ni, V, As, Pb, Co, B, Ce) had a potentially very high skin contact risk. In the Refractory unit, the main products handled consist of a mixture of chemical elements with potentially very high inhalation and skin contact risks for (CaO, Na2O, K2O).

In our study, after calculating the potential risk score for each chemical product, we calculated the unit’s risk score by summing up all the scores and presented it as a percentage for each unit. This showed that the Electric Arc Furnace unit had the highest potential risk (63.6%). The inhalation risk was very high for the Refractory unit (62.8%), and the skin contact risk was highest in the Continuous Casting Machine unit.

It’s important to note that cadmium and mercury were not found in the composition of steel, which contradicts the literature where these two components are expected to be present. This might be due to the fact that cadmium and mercury are emitted during the steel manufacturing process without being detectable components in the spectrometer analysis. (TOXEV)

Conclusion

This work allowed for the assessment of chemical risks in a steel plant, part of a large company specializing in the production of rebar, billets, and wire rod. The results demonstrated the diversity of chemical products, including metals, gases, refractory materials, and solvents, as well as variability in exposure levels depending on the units and job positions, both through inhalation and dermal contact.

A prevention policy that prioritizes the replacement of hazardous chemicals with less dangerous ones and modifies the work processes should be established. Enhanced monitoring of exposed workers complements technical prevention measures. Employers should maintain an up-to-date list of the products used and require suppliers to update safety data sheets.

This simplified methodology from INRS allowed us to conduct a preliminary and probabilistic assessment of chemical risks. Atmospheric monitoring should complement our study. Clinical results indicated the significance of respiratory symptoms in steelworkers, suggesting subacute exposure. Specific investigations of the nervous system can provide insights into subclinical exposure to detect early neurological effects. However, we cannot definitively conclude that the clinical symptoms observed result from exposure to the handled chemical products. Additional case-control studies should be conducted in the future to provide a more comprehensive understanding.