Principles of Occupational Hygiene Essay Example
Principles of Occupational Hygiene Essay Example

Principles of Occupational Hygiene Essay Example

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  • Published: May 19, 2017
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Safe Work Australia (SWA) is the current authority for workplace exposure standards in Australia. Previously known as The Australian Safety and Compensation Council (ASCC) from 2005-2009 and The National Occupational Health and Safety Commission (NOHSC) from 1985-2005, NOHSC was responsible for assessing and setting workplace exposure limits in Australia by using an exposure database obtained from The American Conference of Industrial Hygienists (ACGIH) and The United Kingdom Health and Safety Executive (HSE). These organizations were selected due to their vast experience and research on occupational exposures, with ACGIH specifying exposure limits as Threshold Limit Values (TLV), determined through animal and human research, industry knowledge, and epidemiology. Today, Safe Work Australia develops exposure standards based on work health and safety statistics alongside ongoing formal research into workplace substance ex



A thorough analysis of statistics reveals a noteworthy increase in adverse health effects that are caused by a particular substance. This triggers SWA to evaluate the current exposure limit to ascertain whether it is sufficient to safeguard the workforce against harm. Feedback from the community is sought on the proposed changes to exposure limits. Exposure Standards, as stated in NOHSC: 1003, 1995, are utilized as limits for workplace exposures. If the government establishes a significant risk to workers, legislation such as Acts and Regulations are enacted to specify exposure limits. An example of this is lead which has a detailed exposure limit of 1. 45 ? mol / L (30? g / dL) listed in part 7.

The Model Work Health and Safety Regulations 2011 contain exposure limits, which may also be incorporated into laws through standards such as the Adopted National Exposure Standards for Atmospheric Contaminants in

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the Occupational Environment (NOHSC: 1003, 1995). Chapter 7 of the Regulations 2011 mentions this standard. Inhaling dusts ranging from 1? m to 100? m in diameter found in workplaces can have negative effects on workers' health according to Tillman (2007). ISO 7708:1995 specifies three dust size fractions relevant to health-related sampling, namely inhalable fractions with an aerodynamic diameter less than 100? m. Inhalable dust refers to airborne material that enters the respiratory tract through the nose or mouth and lodges there.

Particles of dust that are smaller than 10?m in diameter can enter the respiratory tract and parts of the lungs, including the bronchi. Those with a diameter less than 5?m can penetrate deeper into the lungs where gas exchange occurs and may even enter the bloodstream through the lungs. The size of a dust particle is determined by its source material and work process.

In the workplace, dusts are commonly categorized into inhalable or respirable forms to assess their impact on health. The inhalable fraction pertains to thoracic fractions and can include inhalable dusts with a diameter of up to 100? m that may settle in the nose, throat, and upper airway. This could lead to immediate toxicity or irritation. For the past three decades, woodwork has been identified as a potential source of respiratory illnesses. Workers who are exposed to inhalable wood dust may suffer from negative health consequences such as asthma, bronchitis, or impaired lung function (Monier et al., 2008; Skovsted et al., 2000).

Wood dust particles seldom reach the gas exchange regions of the lungs due to their larger size. However, the alveoli and other gas exchange areas are susceptible to deposition of respirable

dust particles, which can result in severe and chronic health issues. These types of diseases typically do not exhibit immediate symptoms, but rather develop over prolonged periods of exposure to respirable dust particles.

The risk of respiratory disease caused by particles smaller than 5? m, such as silicosis, is similar to that of other minerals like asbestos (Busnick, 2011). Prolonged exposure to silicosis can lead to various health problems including bronchitis, emphysema, chronic obstructive pulmonary disease and even cancer. To monitor personal exposure to both respirable and inhalable dust fractions in the workplace, Australian Standards AS 2985:2009 and AS 3640:2009 provide guidance on gravimetric sampling of breathing zones (Question 2: Part B Reference to Australian Standards).

To measure the breathing zone, one must consider a 300mm radius in front of the face that extends from the ear midpoint. Before use, all equipment used for sampling must be calibrated. To ensure accuracy and consistency, samples should be sent to an accredited laboratory certified by NATA. Equipment necessary for monitoring respirable dust in the workplace includes a filter that collects the sample, a size-selective sampler, and a pump that passes air through the filter. Personal sampling instrumentation places the filter within the breathing zone and connects it to a pump through flexible tubing. A miniature cyclone that conforms to the sampling efficiency curve, such as a BCIRA, is needed to sample respirable dusts.

To achieve the best outcomes, it is advisable to make use of filter sizes that have a diameter of 25mm. However, if it suits the sampling head, a filter with a diameter of 37mm can also be used. It is essential to choose filters with pore sizes

no larger than 5?m so as to ensure accuracy and prevent any disruptions caused by electrostatic charge, moisture variations or loss of either filter or sample during analysis. One must handle filters carefully during transportation to avoid any loss of sample. Sampling pumps should maintain a constant flow rate within ±0.1L/min throughout the entire sampling period while pulsation rates range between 0.

Individual exposure to 0.2 L/min air flow should be sampled for as long as possible, ideally for 8 hours. The following sampling procedure should be followed: 1. Record pump start time, size-selective sampling number, filter, pump identification, initial flow rate, secondary flow rate used, and worker identification with a description of their location. 2. Turn on the pump.

Attach the sampling pump to the worker and secure the sampling device with a pre-weighed filter in the breathing zone. Check that all tubing is not damaged or blocked, and during sampling, make sure to keep track of the work being done, any risk control measures used, and other relevant information. Before stopping the pump, calculate and document the flow rate through the sampling device, as well as what time it was stopped.

A variation in flow rate exceeding ±5% renders the sample invalid. The sample device or cassette shall be stored in a dust-free container that is already labelled.

To monitor inhalable dust in the workplace, the sampling system equipment required includes a filter, a size-selective sampler, and a pump. The filter collects the sample, while the pump passes air through it. Personal sampling instrumentation features a filter located within the breathing zone, connected to the pump via flexible tubing. After allowing the filter to reach

equilibrium overnight, perform routine weigh checks with samples and blank filters. Record the weights in milligrams.

The IOM inhalable dust sampling head, produced by the UK Institute of Occupational Medicine in Edinburgh, is composed of a special cassette that houses a filter and a single entry orifice. In order to conduct a successful sampling procedure, a pump capable of maintaining a consistent flow rate of 2.0 ±0. L/min throughout the entire sampling period must be used. The sampling period should ideally last as long as possible, but will be set to 8 hours to accommodate individual exposure. The exact procedure for sampling will consist of one step.

Begin the sampling process by turning on the pump and recording pertinent information, including the sampling device number, filter and pump identification, date, pump start time, initial flow rate, secondary flow rate used, and worker identification along with a description of their static location. 2. Connect the sampling pump to the worker. 3. Secure the sampling device with a pre-weighed filter to the worker's breathing zone, ensuring that all tubing is free from leaks and kinks. 4. Proceed with sampling.

During the sampling process, it is important to take note of the activities being carried out, the precautionary measures established, and any other pertinent information. Before shutting down the pump, make sure to document the time and re-evaluate and document the flow rate via the sampling equipment. A sample is deemed unusable if there is a fluctuation of more than ±10% in the flow rate.

6. A container that is labelled and free of dust will hold the sample device or cassette.
After allowing the filter to reach equilibrium overnight, weigh

checks should be conducted with both the samples and blank filters on a routine basis, and record the weights in milligrams.

Question 3: Part A

During the process of smoothing poured concrete surfaces, construction workers who utilize handheld electric grinders are exposed to hazardous dust. This dust is known as respirable crystalline silica dust and has caused a significant number of negative occupational health effects. There have been many documented cases of death from silicosis, which is a disease that results in scarring of the lungs (AIOH, 2009). In Australia, the occupational exposure of 0 is detailed by the Hazardous Substances Information System (HSIS) and NOHSC (1995).

The limit for respirable crystalline silica is 1 mg/m3 TWA, which is crucial in determining if workers are exposed to harmful levels of silica dust that could negatively impact their health. Exposure measurements can be determined through workplace material surveys, observations, analyses of employee complaints or symptoms, and occupational environmental reports, as outlined by NIOSH in 1977. It is essential to establish comparable exposure groups when identifying the need for exposure measurements since it aids in the accurate identification of exposure levels.

Utilizing exposure groups can decrease program costs by conducting sampling within them. Creating high risk groups, such as process operators, and low risk groups, such as administration, guarantees a control group for the monitoring program. To safeguard workers' health from silica dust exposure, unbiased and representative samples of total employee exposure are necessary (NIOSH, 1977). Thus, monitoring programs based on statistics maximize exposure measurement resources and guarantee efficient sampling strategies and assessment of measurement data.

The Occupational Exposure Sampling Strategy Manual (1977) outlines the necessary steps for developing

a statistically based monitoring program, which includes the following three key elements: determining the need for exposure measurements, devising an exposure measurement sampling strategy, and conducting statistical analysis of exposure measurement results. To determine the need for exposure measurements, various methods can be employed such as workplace material surveys, workplace observations, analysis of employee complaints or symptoms, and occupational environmental reports. It is essential to identify similar exposure groups to accurately measure exposure levels while minimizing costs. Categorizing employees into high and low-risk groups enables comparison and control within the program for monitoring purposes.

When creating a statistical monitoring program, it is crucial to consider the strategy for selecting employees to sample. NIOSH (1977) provides specifications for the number of samples needed at a 95% confidence level based on group sizes. For instance, if there were two high-risk groups of manual concrete surface grinders, each with 40 employees, then 17 samples would be required from each group. In addition, if a control or administrative group comprised 23 employees, then 14 samples would be needed.

NIOSH specifies sampling guidelines to minimize program costs while maintaining sampling program integrity, including adhering to specific requirements for crystalline silica dust. These requirements include using a 2 L/min sample pump flow rate, a 10 mm cyclone air sampling device with pre-weighted 37mm cassette, and a process for cleaning and monthly leak testing of the cyclone using a pressure gage. Samples should be taken within the employee's breathing zone and assessed by a NATA accredited laboratory. NIOSH recommends three methods for sampling measurement in order of precision and accuracy: full period consecutive samples measurement, full period single sample measurement, and...

The ideal

monitoring program would involve the use of full period consecutive samples measurement for both partial and grab samples. This method provides the narrowest confidence limits, thus leading to statistical benefits as indicated by NIOSH (1977). Consequently, exposure measurement results should be analysed with the relevant exposure limits in mind, particularly for silica dust where employee exposures exceeding 0 should be taken into consideration.

Exposure to silica dust at levels exceeding 1 mg/m3 during an 8-hour work day may lead to adverse health effects. To accurately measure exposure, samples with a 95% confidence interval rating are recommended. Whenever workers are found to exceed the silica dust exposure limit, controls must be implemented to mitigate risks to worker health. Additionally, the monitoring program should include regular follow-up sampling whenever changes are made to the workplace, work practices, or processes.

According to NIOSH (1977), if the workplace environment remains unchanged, workers below the exposure limit should be sampled at least every 2 months, while those above the limit should be sampled once a month. However, testing frequency may vary based on professional judgment. As for controls in manual concrete surface grinding, the first step is to determine if modifying or replacing the current process is feasible and practical. This involves examining product elimination or substitution, changes to the grinding process, or equipment and technology alterations. Since crystalline silica is often present in the working area, eliminating or substituting control measures is typically unrealistic. Hence, implementing additional engineering controls, administrative controls, and PPE use can help reduce exposures.

Determining the practicality and costs of implementing controls against the expected health benefits is crucial. Various studies have shown that the reduction of silicosis

incidents has been successful through control measures. This reduction is attributable to regular medical surveillance, compliance with a regulatory exposure standard, prohibition of high-risk tasks (such as sandblasting and using silica flour in foundry operations), and utilizing suitable dust suppression systems like ventilation and wetting down (AIOH 2009). Similar control principles apply to all mechanically generated dust exposures, including crystalline silica (Akbar-Khanzadeh et al, 2007).

To perform manual concrete surface grinding, recommended controls include designing and implementing processes to reduce the emission, release, and spread of crystalline silica dust. Personnel should be positioned away from the dust, either in enclosed and filtered cabins or in the opposite direction of the emission draft. Sharp cutting tools should be used to minimize dust generation, and wet processes can prevent it altogether. Additionally, water suppression and ventilation should be utilized to control dust release. Good housekeeping practices are essential for preventing dust build-up. Personnel must receive training on the health effects of silica dust, as well as its control measures. Where exposure control is not possible, suitable PPE (such as a P1 or P2 half face respirator) in combination with other control measures is recommended. It is also important to provide training on the use and limitations of respiratory protective equipment. Face fit testing and a clean shaven face are advised as per AS 1715 (2009).In the Journal of Occupational and Environmental Hygiene, a study was conducted by Akbar-Khanzadeh et al. (2007) which compared the levels of crystalline silica dust and respirable particulate matter during indoor concrete grinding under different conditions: wet grinding, ventilated grinding, and uncontrolled conventional grinding.

The AIOH Exposure Standards Committee published a position paper regarding Respirable

Crystalline Silica and Occupational Health Issues. The paper can be found in Volume 4, pages 770-779. The American Conference of Governmental Industrial Hygienists (ACGIH) provides TLV (Threshold Limit Value) Resources that can be accessed through their website. The paper was published in Tullamarine, Victoria, Australia.The website provides access to AS/NZS1715:2009, which covers the selection, use, and maintenance of respiratory protective equipment. Another standard, AS2985:2009, can also be accessed through the website and pertains to workplace atmospheres and the method for sampling and determining respirable dust through gravimetry. These resources were all accessed on September 16, 2012.

Accessed via UOW library on 16 September 2012, AS3640:2009 presents a workplace atmospheres sampling and gravimetric determination method for inhalable dust. In a Safety Compliance Letter article by Busick (2011), General Industry's Approach to Crystalline Silica is crystallized. Further, the Health and Safety Executive (HSE) in 2005 highlights EH40/2005 Workplace exposure limits.

The source for health-related sampling definitions regarding particle size fractions in air quality is available at, which cites ISO 7708:1995(E) and was accessed on September 16th, 2012. Additionally, an article by Kaelin and Liang from 2008 titled "New OSHA program targets silica, other blast cleaning chemicals" can be found in the Journal of Protective Coatings ; Linings.

Accessed on September 17, 2012, the article 'Occupational asthma to wood dust' written by Monier, S., Hemery, M., Demoly, P., and Dhivert-Donnadieu, H in 2008 in the Revue Francaise D Allergologie Et D Immunologie Clinique (vol. 48, no. 1, pp. 31-34) reported on cases of occupational asthma caused by wood dust. In addition, the US Department of Health, Education and Welfare's 'Occupational Exposure Sampling Strategy Manual' from 1977 was also

accessed on the same day.

The National Occupational Health and Safety Commission (NOHSC) implemented national exposure standards for atmospheric contaminants in the workplace environment in 1995, which can be found in NOHSC: 1003. This information is also available on the SafeWork Australia website, Furthermore, Skovsted et al. published an article on wood dust hypersensitivity in the journal Allergy with an ISSN of 1398-9995 and a volume date of November 2000.

Tillman, C. (2007). Principles of Occupational Health and Hygiene (p. 1089). Crows Nest: Allen & Unwin.

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