Enhancing Safety in Metalworking: A Case Study on Occupational Exposure Monitoring and Control for Metalworking Fluids

In the dynamic world of heavy industry, where complex operations such as closed die forging and precision machining of colossal crankshafts reaching up to 750Kg are commonplace, the occupational exposure risks cannot be ignored. This case study takes a deep dive into the potential hazards in the sector, focusing specifically on exposure to metalworking fluids.

This segment of the industry is remarkable for its integration, with services offered ranging from initial design to delivery of the finished product. Industries served span agriculture, off-highway, marine, power generation, and mining sectors. The operations are carried out by highly skilled and specialized personnel across two divisions, producing a wide range of products including various crankshafts, connecting rods, axle beams, and forgings for mining applications.

However, in such an industrial environment, where large components are being processed, exposure risks are inherent and the control over these may be limited due to the scale and complexity of operations. Particularly, exposure to metalworking fluids presents a significant occupational hazard that needs diligent assessment and mitigation.

Metalworking fluids (MWFs), typically used for cooling, lubricating and removing metal particles during machining operations, are a crucial component of the industrial process. However, their application often results in workers' exposure through inhalation of airborne mists, dermal contact, or accidental ingestion. Chronic exposure can lead to various health problems, including dermatitis, respiratory issues, hypersensitivity pneumonitis, and in some cases, increased risk of certain cancers. Thus, understanding these risks and implementing stringent occupational exposure monitoring becomes a pressing need in this sector to ensure the health and safety of the workforce. This case study aims to explore these risks in detail, examining the current practices and outlining potential improvements in exposure monitoring and control strategies.

Metalworking fluids (MWFs) are complex mixtures with diverse components depending on the specific application. They generally contain a base fluid (which can be mineral oil, synthetic, semi-synthetic, or water), along with a variety of additives. Each of these constituents can pose individual health risks upon exposure.
 
1. Base Fluids: Mineral oils are derived from petroleum and can cause skin irritation or dermatitis. Synthetic fluids, although generally less irritating, can still cause skin disorders and may contain other harmful constituents.
 
2. Additives: MWFs contain many additives designed to enhance their performance. These can include biocides, corrosion inhibitors, anti-weld agents, stabilizers, and emulsifiers among others. Exposure to these can lead to a range of health issues. For example, biocides are used to kill bacteria and fungi in the fluid but can cause respiratory and skin irritation in workers. Corrosion inhibitors can also be irritants and may be toxic.

3. Metal Particles: As the MWFs are used in machining processes, they can become contaminated with tiny metal particles. When these become airborne in the form of a mist, they can be inhaled by workers leading to respiratory issues.

MWFs also have the potential to become contaminated with harmful microbes, presenting additional health risks.

1. Bacterial Contamination: Over time, bacteria can multiply in MWFs, particularly in water-based fluids. These bacteria can produce endotoxins which, when inhaled or come into contact with the skin, can cause symptoms ranging from flu-like illnesses to severe respiratory conditions.

2. Fungal Contamination: Fungi, including mould and yeast, can also grow in MWFs. Exposure to these organisms can lead to a variety of health problems, including allergic reactions and lung infections.

Given the myriad of potential chemical and biological contaminants present in MWFs, regular monitoring of worker exposure is crucial. Understanding the composition of these fluids and how they can affect the human body is the first step in effectively mitigating these risks. Protective measures, proper handling and storage procedures, as well as regular fluid maintenance and replacement, can significantly reduce the risk of adverse health effects.

Our method

In assessing the occupational exposure to metalworking fluids, our team applied a robust methodology that employs a combination of collection techniques and analytical methods. We utilized 25mm Mixed Cellulose Ester (MCE) filters held within IOM cassettes for the aerosol sampling of Water-Mix Metal Working Fluids. These filters allow for effective capture of the airborne particulate matter and aerosols associated with the fluids in use.

The collected samples were then analysed in line with the Methods for the Determination of Hazardous Substances (MDHS) 95/3 guidelines, using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). This method allows for the detection and quantification of a broad spectrum of elements, thereby providing comprehensive insights into the potential exposure risks.
 
When discussing exposure limits, it's important to note that due to the complex and variable nature of Metal Working Fluids, including both mineral oil and water-mix forms, there isn't a current UK Workplace Exposure Limit assigned. Variability in their composition, potential for contamination during industrial use, and lack of evidence for a level of inhalation exposure that doesn't lead to health effects, makes deriving a health-based occupational exposure limit unattainable.

Previously, a guidance limit of 1mg.m-3 (8-hour TWA) for water mix metal working fluids was suggested in HSE publication HSG 231. However, this was withdrawn upon recognizing the potential for respiratory effects at concentrations below this guidance limit.

In the absence of a UK limit, the US National Institute for Occupational Safety and Health (NIOSH) limits can be considered for comparative purposes: 0.5 mg.m-3 as 'total' aerosol for metal working fluids and 5 mg.m-3 for mineral oil mist. Despite having no legal basis in the UK, these values can serve as a guide in risk assessment. Nonetheless, according to the principles of Control of Substances Hazardous to Health (COSHH), exposures should always be maintained as low as reasonably practicable, irrespective of any set guidelines or limits.
 

Available guidance

A variety of guidance materials is available to support the effective management of exposure risks associated with metalworking fluids in the industrial sector. These resources are designed to ensure the safety of employees and comply with health and safety regulations. They cover a wide range of topics, from best practices for handling and disposing of these substances, to employee safety, and emergency procedures.

The following resources provide comprehensive guidance on various aspects of working with metalworking fluids:

1. Machining with Metalworking Fluids - COSHH e-tool: An online tool for risk assessment and compliance with COSHH regulations.

2. UKLA-HSE-Good-Practice-Guide-for-Safe-Handling-and-Disposal-of-Metalworking-Fluids.pdf: A guide outlining safe procedures for the handling and disposal of metalworking fluids.

3. HSE COSHH MW0: Guidance document focused on a specific aspect of managing exposure to metalworking fluids.

4. HSE COSHH MW1: Another focused guidance document on controlling exposure to metalworking fluids.

5. HSE COSHH MW2: Detailed resource on a different aspect of exposure control.

6. HSE COSHH MW3: Resource providing guidance on yet another aspect of exposure control.

7. HSE COSHH MW4: Document containing guidance on another distinct facet of managing metalworking fluid exposure.

8. HSE COSHH MW5: Resource detailing procedures and controls for another specific aspect of exposure management.

9. Metalworking Fluids - HSE: Comprehensive overview of potential health risks and advice on reducing exposure.

10. INDG365 - Working Safely with Metalworking Fluids: A Guide for Employees: Guide aimed at workers to ensure self-protection while working with metalworking fluids.

Our observations and findings

Based on our observations and findings, we identified that typically two operatives work on the Veroco Grinding machines. Their role involves setting up the components in the machine, programming the tool, and supervising the machining process. The responsibility of checking metalworking fluids is outsourced to a contracting company.

These operatives are likely exposed to hazardous components linked to water-based metalworking fluids, specifically PENCOOL Ultra S430, which includes sodium salts, alcohols, and Iodopropane Butyl Carbamate. Ventilation in the workspace is primarily general area ventilation, and there are no roof-mounted ventilation fans near the machinery. The machines do not have Local Exhaust Ventilation (LEV) systems installed.

Safety measures taken by the operatives include wearing surgical gloves to minimize contact with the fluids and donning mandatory overalls and eye protection. The environment is generally clean, although there is evidence of aerosol settlement on surfaces near the machine. Fluid assessments are done biweekly, including control of bacterial levels. The operatives are also part of a regular health surveillance program, which includes dermal checks and audiometry.

Air monitoring results under normal operating conditions indicate that personal exposure levels to the water-based metalworking fluids remain within US Occupational Exposure Limits (OELs). However, as exposure exceeds 10% of the workplace exposure limit, this is still considered significant.

One of the key findings from this study is the absence of adequate engineering exposure controls. Notably, the Veroco Grinding Machines lack sufficient LEV systems, which are essential in controlling exposure to aerosols. Consequently, improvements in this area are strongly recommended.

Recommendations

Our recommendations to improve safety and reduce exposure to metalworking fluids (MWF) in the workplace are as follows:
 
First, we recommend a review of the regularity of microbiological testing. Currently, it is carried out on a monthly basis, but a weekly schedule could potentially offer a better control of bacteria levels in the MWF.

Next, the degree of enclosure at some of the CNC machines could be enhanced. This measure would help contain aerosol spread and should be implemented within a time frame of 1 to 3 months.
To further reduce exposure, the installation of Local Exhaust Ventilation (LEV) systems, specifically FilterMist extraction units, should be considered for CNC machines that currently lack extraction. Ensure these systems are thoroughly examined and tested in accordance with the COSHH Regulation 9.

To decrease the risk of aerosolized particles entering breathing zones, we suggest minimising or completely avoiding the use of compressed air guns for cleaning. Alternative cleaning methods that don't blow swarf and cutting fluids should be investigated.

In addition to these controls, it's vital to ensure a suitable dermatological and inhalation health surveillance programme is in place for personnel regularly working with water mix MWF.
To further protect the skin of operatives, we recommend providing suitable re-moisturising and barrier creams. Alongside this, appropriate information, instruction and training regarding the risks of skin exposure to mineral oils should be offered.

Lastly, it is crucial that all operatives receive specific training regarding the risks associated with working with MWF. Resources like the HSE publication INDG 365 'Working safely with metalworking fluids: A guide for employees' can be useful for this purpose. Further guidance on MWF can be found in the HSE guidance, 'COSHH Essentials for machining with metal working fluids'.
In conclusion, a comprehensive approach that combines preventive measures, engineering controls, and health surveillance will help reduce the risk associated with exposure to metalworking fluids.
 

Value delivered

Our comprehensive occupational exposure monitoring for metalworking fluids has provided invaluable insights to our client. The detailed analysis of the workplace environment, the specific tasks of the operatives, and the exposure levels of harmful substances allowed us to identify areas of risk that could have otherwise gone unnoticed. We were able to recommend practical, actionable solutions, many of which can be implemented immediately or within a short timeframe. These recommendations are designed to enhance the safety and well-being of their workforce, while ensuring regulatory compliance. Furthermore, we provided resources for the training and education of the workforce, empowering the employees to better protect themselves from potential hazards. In the long run, these improvements will contribute to a safer and healthier workplace environment, potentially reducing downtime due to health-related issues, and enhancing overall productivity.