Postgraduate occupational health research studies

Background: Occupational noise-induced hearing loss (ONIHL) is one of the most common occupational health diseases affecting miners in South Africa. There are challenges around the high prevalence of ONIHL in South African miners that have been linked with excessive noise exposure levels, and ineffective HCPs, with poor quality records that impede accurate monitoring of miners at risk of developing ONIHL. The main aim of this study is to explore risk assessment practices for ONIHL at a large-scale platinum mine in Limpopo province, South Africa, so to propose an early identification predictive model for ONIHL. Objectives: The objectives of this research were: 1. To describe the audiometry surveillance system (including record keeping) in a large South African mine over a five-year period (2014-2018) 2. To identify factors that impede the early identification of ONIHL, from mine records captured within an information management system, from 2014-2018 3. To determine if the mine used a proactive data management system (PDMS) to identify miners at risk of ONIHL 4. To establish how the mine manages miners presenting with risk factors associated with ONIHL, within the HCP 5. To propose an early identification predictive model for ONIHL in the mining industry Methods: This was a respective cohort study. Data were accessed from one platinum mine in Limpopo province, South Africa. The individual miners’ audiometry medical surveillance (health and safety) and occupational hygiene records (N=305) for the period 2014 to 2018 were analysed. Thereafter, the mine’s two datasets, which contained miners’ diagnostic audiometry records (N = 1 938) and a subset of records of miners diagnosed with ONIHL (n = 73) were analysed. STATA was used for data analysis, but the data were analysed differently for each study objective. For objectives 1 and 2, data were analysed using descriptive statistics. For objective 3, miners’ risk factors associated with ONIHL were identified and described using the functional risk management structure, thereafter, a logistic regression model was used with the baseline percentage loss of hearing (PLH) margins of 0% - 40% (in 5% increments) to estimate the adjusted predictions for miners at risk of developing ONIHL, and the contribution of noise exposure as a risk for ONIHL was estimated using a two-way sample proportion test. For objective 4, ethical principles prescribed by the Health Professions Council of South Africa, the Protection of Personal Information Act, and the National Health Act (Act No.61 of 2003), that guide data access for medical research were applied to the mine’s audiometry medical surveillance data to identify ethical challenges related to data access. For objective 5, miners’ demographic and occupational exposures (noise and platinum mine dust) were analysed to examine their association to standard threshold shift (STS) and miners’ age, sex, PLH, and dust and noise data were used to predict STS, using a linear mixed effects regression model. Results: The results are detailed in the papers published and submitted for publications. The abstract provides a summary of findings drawn from the papers. In paper 1, most of the miners were male (89.6%), and more than 50% were younger than 41 years. There was inaccurate and insufficient recording of risk factors for hearing loss in the medical surveillance records. Some miners were exposed to dangerously high noise levels (as high as 104 dBA). Miners as young as 21 years of age were diagnosed with ONIHL. In Paper 2, we identified and described risk factors associated with ONIHL and calculated risks for ONIHL. A linear regression model estimated miners’ risks of ONIHL at baseline. Miners with a 0% baseline PLH had a 20% predicted risk of ONIHL; and a 45% predicted risk if they had a 40% baseline PLH. Seventy-three miners had a confirmed diagnosis of ONIHL. Paper 3 showed changes in the miners’ standard threshold shift (STS) ranging from 8.3 dBHL at baseline (2014/2015) to 10 dBHL in 2016, with no changes thereafter. Less than 10% of the miners were at risk of ONIHL (>26 dBHL; STS). A linear mixed effects regression model estimated that male miners’ STS were more associated with ONIHL than their female counterparts. When combined, age, PLH, noise exposure and years of exposure were associated with STS at < 10%. There was no statistically significant association between PMD and STS in hearing. In the fourth paper, a lack of clearly defined medical ethics policies around data access for research, and Protection of Personal Information Act (POPIA) regulations and their application on miners’ audiometry, occupational hygiene, and medical data restricted data access for the latter. In this paper, different data access practices for different datasets, with stricter restrictions, were applied to miners’ medical surveillance records (medical conditions and treatments). Conclusion: Systems need to be set in place to ensure integrated accessing, analysing, and reporting miner-specific demographic, medical, occupational, and non-occupational exposure information. Annual surveillance records should be complete, accurate and should include any ear-related conditions, such as impacted wax and middle ear infections. The machine learning systems (MLSs) used for HCP risk assessment are partially effective in reducing risk and preventing ONIHL. To improve efficiency, all risk factors associated with ONIHL should be included in the mine’s electronic data recording system. The use of percentage loss of hearing (PLH) to track miners’ hearing may be sufficient for ONIHL compensation, but it is not adequate for identifying early signs of any type of occupational hearing loss, including ONIHL. Thus, the use of STS will ensure tracking of miners’ hearing and the identification of early signs of occupational hearing loss. Age, sex, years of exposure to noise, and noise exposure levels combined effects and strength of association can be used to predict STS for this group of miners. Our findings may be used to measure the efficiency of the mine’s HCP, and its efforts in preventing ONIHL among miners

Flour dust is a hazardous substance and refers to the particles that are created when cereals or non-cereal grains are milled finely. Research shows that excessive inhalation of flour dust is linked to various adverse respiratory health effects – however, most of this research has been conducted internationally. This study aims to determine the associated respiratory outcomes with occupational exposure to flour dust, further adding to the limited South African literature in this field. The focus of this study is at a flour mill located in the Phoenix Industrial Park, Durban, KwaZulu-Natal. This is a descriptive cross-sectional study conducted at one point in time. The study sourced quantitative data. A sample size of 63 employees was selected from a total population size of 70 using the simple random sampling strategy, in which the margin of error was set at 5%. This study sought to determine the respiratory health of employees in a flour mill, to analyse retrospective spirometry data from medical records of employees at the flour mill, to identify factors contributing to increased exposure to flour dust and to determine the relationship between occupational exposure to flour dust and the associated respiratory outcomes, using retrospective spirometry data and occupational hygiene reports. This study has established a strong relationship between site of work (which determines the level of exposure to flour dust) and the prevalence of respiratory issues. Retrospective environmental monitoring reports have highlighted the departments which presented consistently high flour dust levels, namely, the milling, packing and maintenance departments. Unsurprisingly, these departments also reported a higher prevalence of breathing complications, chest tightness, rhinitis, dry cough, and conjunctivitis as well as reduced mean Forced Expiratory Value per 1 second/ Forced Vital Capacity (FEV1/FVC) values - highlighting that the department played a role in adverse respiratory effects. The Coronavirus pandemic increased mask usage, therefore, FEV1/FVC values were slightly better in 2020 when compared to those of 2019. Evidence has revealed that apart from the level of exposure to flour dust, other factors are shown to have influenced results, such as, age, Personal Protective Equipment (PPE) awareness and training, novel Coronavirus pandemic, duration of employment, smoking habits, mixing departments and a lack of a flour dust Occupational Exposure Limit (OEL).

In the field of occupational hygiene, light and the use of different lighting types have become fundamental control measures in reducing risks to health and safety while at the same time promoting increased productivity within the workplace. Illuminance meters are used in surveys to quantify the amount of light illuminating an object, surface, or general workplace to determine if illumination in the workplace complies with regulations and standards. Accurate illuminance measurement requires important considerations, such as the calibration conditions of illuminance meters, the spectral response of illuminance meters and the specific light source being measured. The general aim of this study was to measure and compare illuminance values obtained from the Goldilux auto-ranging light meter (GL) (MIT, South Africa), Goldilux-LED auto-ranging light meter (GL-LED) (MIT, South Africa) and the Konica Minolta CL-70f illuminance meter (KM CL- 70f) (Konica Minolta, Japan) under controlled laboratory conditions. The objectives of this study were: (i) to measure and compare the illuminance levels of halogen incandescent lamps (hICLs), compact fluorescent lamps (CFLs) and light emitting diodes (LEDs) using the GL (MIT, South Africa), the GL-LED (MIT, South Africa) and the KM CL-70f (Konica Minolta, Japan); (ii) to measure and compare the illuminance levels of low-, medium-, and high-output hICLs, CFLs and LEDs, and (iii) to measure the colour correlated temperatures (CCTs) and spectral wavelengths of each of the above-mentioned light sources with the KM CL-70f illuminance meter (Konica Minolta, Japan). The GL, GL-LED, and KM CL-70f were used to measure low-, medium-, and high-output hICLs, CFLs and LEDs precisely one metre away from the selected lamps under laboratory conditions. Background illumination in the test facility was 0 lux. Lamps were individually measured for two minutes, or until the values on the illuminance meter had stabilised. Lamp measurements were repeated three times (n=9 per lamp). Results of the GL, GL-LED, and KM CL-70f were similar when measuring low- and mediumoutput hICLs. Statistically significant differences in illuminance values were observed when measuring high-output hICLs and all CFLs and LEDs. The degree to which illuminance values differed, increased when measuring lamps with higher outputs. Spectral wavelength measurements indicate that CFLs and LEDs have entirely different spectral qualities in comparison to the traditional ICL and hICLs. To achieve accurate measurements of modern lamps, such as CFLs and LEDs, illuminance meters having a spectral response capable of measuring the entire visible spectrum should be used. Furthermore, due to the differences in spectral wavelength qualities of lamps, illuminance meters should be calibrated to measure modern lamp types such as CFLs and LEDs. There is a need for the development of regulations and standards that define which qualities of illuminance meters are required for accurately measuring light within the workplace. Currently, there is limited information considering the minimum required quality indices such as the spectral distribution qualities or the spectral mismatch factor that illuminance meters should conform to when measuring light in the workplace. The need for development of regulations and standards, as well as the application of the GL, GL-LED and KM CL-70f in the workplace were recommended. A study limitation and future studies were also discussed.

Background: During the processing and refining of platinum (Pt), workers are exposed to respiratory sensitizing platinum salts. The most toxic of these platinum salts are tetra- and hexachloroplatinate, especially when attached to potassium. Although multiple researches have associated the respiratory exposure route with the development of respiratory sensitization to platinum salts, the notion of an additional dermal route of exposure was suggested. This notion was suggested due to active dermal exposure to these platinum salts in many instances and the high sensitization occurrence during low levels of respiratory exposure. Dermal exposure has previously been associated with the development of respiratory sensitization in animal studies Subsequent in vitro studies investigated the permeation of potassium tetrachloroplatinate through intact abdominal skin and substantiated the plausibility of the dermal route of exposure contributing to platinum absorption. However, the more toxic sensitizer, potassium hexachloroplatinate has not been investigated regarding its permeation profile. Aims and objections: In vitro laboratory experiments were conducted to investigate the permeation profile of potassium hexachloroplatinate (K₂PtCl₆) through full thickness human abdominal skin. The research objectives were to quantify the permeation of potassium hexachloroplatinate by utilizing the static Franz diffusion cell method, to calculate the percentage of platinum retained in the skin, and lastly, to evaluate the effect of exposure duration on the permeation of platinum at 8-, 12- and 24-hour intervals. Methods: Intact abdominal skin from Caucasian female donors, aged between 41 and 48, were obtained after abdominoplasty procedures following ethics approval and informed consent. Utilizing the Franz diffusion compartment methodology, the permeation of 0.3 mg/mL K₂PtCl₆ was quantified at time intervals of 2-, 4-, 6-, 8-, 10-, 12-, 14-, and 24-hours after the onset of the experiment. After the 24-hour extraction, the skin was digested and analyzed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), quantifying the penetrated platinum mass inside the skin. Whereas the permeated platinum mass in the receptor solution was quantified by the means of Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Blank cells not containing the platinum salt, were used for quality control purposes. Results: Platinum permeation, increasing with the continued duration of exposure, occurred through the intact full thickness female Caucasian abdominal skin. The influence of time on permeation was significantly indicated by the 68 % increase in dermal absorption between 8 and 12 hours, and 62 % increase between 12 and 24 hours. The dose percentage of platinum mass contained in the skin after 24-hours was calculated as 3.11 ± 0.25 % (8848.03 ± 699.02 ng). Flux and lag time were calculated as 0.32 ± 0.05 ng/cm²/h and 2.26 ± 0.31 hours, respectively. Conclusion: With the results all aims and objectives were achieved. Results indicating a considerable platinum reservoir forming in the skin together with the short lag time implicated that continuous real-world permeation may occur adding to the body burden of platinum even after removal from the source of exposure. The presence of detectable levels of platinum mass in the receptor fluid at the 2-hour interval further suggested that even short periods of exposure to potassium hexachloroplatinate presents a risk of permeation into the body. Significant increase in mean permeation between 8 and 12 hours was substantial as extended work shifts are commonly implemented. Furthermore, exposure circumstances such as the so called ‘take-home’ effect and the layering of new deposition onto previous deposition on the skin, emphasize the importance of proper decontamination protocols. Indications were made towards a shorter lag time and heightened cumulative mass parameter when utilizing potassium hexachloroplatinate compared to other PGM research. Recommendations were made based on the real-world implications of the results in occupational settings to be applied by future PGM permeation investigations.

Background: AM (Additive Manufacturing) is a process that produces three-dimensional (3D) parts via the layering of materials. To date, there has been little research on the health risks associated with the use of this technology to produce sand moulds for metal casting. Apart from the processing steps involving the AM machine, binder jetting (BJ) of sand moulds includes an additional step which involves the coating of virgin (new) silica sand with sulphonic acid prior to the AM processes. As yet, there is also no information available on the risks concerning the coating process. Both coating and AM processes involve the handling of silica sand, which may result in personal exposure to respirable crystalline silica and particulate matter. Also, furan resin binders used during processing may cause emission of volatile organic compounds (VOCs). Objectives: This study was aimed at determining emissions of and personal respiratory exposure to hazardous chemical substances (respirable crystalline silica, VOCs and respirable particulate matter) during various phases of AM with silica sand as well as during the coating of silica sand prior to AM. Methodology: Analysis of bulk silica sand was performed through the characterisation of particle size and shape using Malvern Morphologi particle analyser and scanning electron microscopy (SEM) while the X-ray diffraction (XRD) process was utilised to determine elemental composition. The Aerosol Particle Counter (APC) and Condensation Particle Counter (CPC) were used to quantify emissions of 0.3 - 10 μm (APC) and 0.01 - ~ 1.0 μm (CPC) sized particles during the coating process as well as pre-processing, processing and post-processing phases. Both personal and area monitoring were performed to measure airborne concentrations of respirable crystalline silica, VOCs and respirable particulate matter during the operator’s shift. Three days were allocated to monitor emissions, personal exposure and area concentrations during coating, while monitoring of the AM process was conducted over a period of five days, where three identical parts were printed. Results: Respirable sized particles were found in all three sand types (virgin, coated and used), with virgin sand having the highest respirable content compared to other sands; d(0.9) = 3.98 ± 0.72 μm vs d(0.9) = 115.00 ± 95.15 μm and d(0.9) = 6.51 ± 2.71 μm, respectively. The quartz content for the three sand types ranged from 92.6 to 97.6%, which made it the dominant mineral. The coating and AM machines were confirmed to emit particles 0.3 μm, 0.5 μm, 1 μm and 0.01 - ~ 1.0 μm. in size. Particulate emissions data indicated that the particle emissions for particles 0.3 μm, 0.5 μm and 1 μm and 0.01 - ~ 1.0 μm in size, increased considerably during the cleaning of the coating machine filter as well as during the opening of the bay door. The particle number concentrations of 0.3 μm, 0.5 μm, 1 μm and 0.01 - ~ 1.0 μm sized particles were higher during the third day of printing compared to the other days, as a result of increased particle number concentrations during post-processing and pre-processing. When comparing the phases, the average particle number concentration was significantly higher during pre-processing compared to other phases. There were no significant differences in emission rates (ERs) but the average ERs for particles 0.3 μm and 0.01 - ~ 1.0 μm in size were slightly higher during pre-processing followed by post-processing and then processing. Personal exposure to respirable crystalline silica during cleaning of the coating machine with compressed air exceeded the South African time weighted average occupational exposure limit-control limit (TWA OEL-CL) of 0.1 mg/m3 (0.112 mg/m³). During cleaning of the AM machine, personal exposure to respirable crystalline silica surpassed the action level (0.07 mg/m3). The personal exposures to HCS (respirable crystalline silica, respirable dust and VOCs) measured during the AM processes were below 10% of their respective OELs. Conclusion: The feedstock material used (silica sand) was regarded as a primary source of exposure. The amount of respirable sized particles found in the silica sand coupled with quartz content of > 90%, made the feedstock material a risk to the health of the AM operator. Both the cleaning methods used during coating and printing led to increased personal exposure to respirable crystalline silica. The AM operator was overexposed to respirable crystalline due to the use of compressed air to clean the filter, and was exposed to respirable crystalline silica exceeding the action level due to the use of a broom when cleaning the AM machine room. The cleaning methods were therefore classified as tasks with the highest risks. Particulate emissions were higher during pre-processing compared to other processes and is of concern since emissions of particles 0.3 μm, 0.5 μm, 1 μm and 0.01 - ~ 1.0 μm in size are a risk to the health of the AM operator as they may deposit in the alveoli, resulting in respiratory dysfunctions. In an attempt to minimise exposure to HCSs during the AM of sand moulds, 18 recommendations were made to the AM facility. Due to overexposure caused by cleaning activities using compressed air, the key recommendation made was for the AM operator to clean the filters in an isolated glove box in order to reduce exposure to respirable crystalline silica, a confirmed human carcinogen.

Background: Outdoor agricultural workers such as farmers and farmworkers have been identified as an occupational group that is at high risk of exposure to solar ultraviolet radiation (UVR) during their work activities. Outdoor workers’ exposure to solar UVR need to be managed to prevent negative health effects such as skin cancer and ocular diseases. Skin colour and melanin content of skin provides a measure of genetic protection against exposure to high levels of solar UVR. Photoprotective measures such as wearing long sleeve clothing, broad-brimmed hats and sunglasses have been identified as measures that can reduce an individual’s exposure to solar UVR if used correctly. The solar UVR exposure of outdoor farmworkers has not previously been investigated in South Africa. Aims and objectives: The general aim of this thesis was to quantify the differences in skin colour and melanin content of facultative and constitutive skin of farmworkers on a macadamia nut and avocado farm in the Limpopo Province of South Africa, as well assessing the existing control measures and practices of those farmworkers together with their occupational exposure to solar UVR to determine if the exposure poses a risk to their health. The specific objectives were: (i) to determine the differences in skin colour (individual typology angle, ITA°) and melanin content (melanin index, MI) between the facultative and constitutive skin of farmworkers using skin bioengineering measurements, (ii) to assess the solar UVR practices, in particular the use of ocular protective measures, of the farmworkers on the farm using questionnaires, (iii) to determine the photoprotection provided by the clothing worn by farmworkers using polysulphone (PSF) badges on the shoulder both under and on top of the clothing and (iv) to assess the personal solar UVR exposure of outdoor farmworkers on the farm during autumn, spring and summer while carrying out their different work activities through polysulphone badges placed on their arms, top of the shoulder and top of any head covering worn. Methods: Outdoor and indoor farmworkers on the farm participated in this study. The skin colour and melanin content of the skin of farmworkers were classified using both a subjective method, namely questionnaires and objective methods namely measurement of ITA°) and MI. Outdoor farmworkers’ use of ocular photoprotective measures was determined with the use of a questionnaire. The photoprotection provided by the clothing worn by farmworkers was measured by placing a PSF badge on the shoulder beneath the clothing and on the outside of clothing and classified according to the requirements of the AS/NZS 4399:2017 standard. The solar UVR exposure of outdoor and indoor farmworkers was measured by placing PSF badges on the shoulder, arm and top of the head during autumn, spring and summer during different work activities. Workers’ exposure was compared with the highest value of the International Commission of Illumination (CIE) occupational exposure limit, namely 1.3 SED (standard erythemal dose). Research ethics approval for this study was obtained from the North-West University Health Research Ethics Committee (NWU-00101-17-A1). Results: Significant differences were found between both the ITA° and MI measured on the constitutive (inner upper arm) skin and facultative (back of the hand) of farmworkers. The skin colour of the majority of farmworkers were objectively classified as falling in the Fitzpatrick Phototype V/Brown. A strong correlation was found between ITA° and MI which indicates that both objective methods are appropriate to determine the skin colour of darkly-pigmented skin. The majority of outdoor farmworkers (80%) never wore sunglasses while working outside. Although more than 70% of outdoor farmworkers wore a hat while working, they preferred to wear a cap rather than a broad-brimmed hat which provides better ocular photoprotection. Statistically significant differences were found between the solar UVR underneath and outside of clothing worn by farmworkers during autumn, spring and summer. Only 5% of clothing did not provide the minimum required photoprotection. More than 75% of farmworkers reported that they removed the long sleeve overall jacket they wear as part of their uniform at some point during the day which exposes their arms to solar UVR. Statistically significant differences were found between the solar UVR measured on the shoulder, arm and top of the head of outdoor farmworkers during spring and summer. The arm received the highest solar UVR exposure during autumn (7.8 SED) while the top of the head received the highest levels during spring (11.6 SED) and summer (13.9 SED). The solar UVR exposure of all body sites exceeded the daily CIE exposure limit for more than 80% of measurements during all three seasons. Conclusion: Skin colour and melanin content of farmworkers in this study was found to provide a high level of genetic photoprotection. It was also found that objective and subjective measurement of skin colour and can both be used to classify the skin colour of an occupational group in order to identify genetic photoprotection in workers. The use of ocular photoprotective measures by the outdoor farmworkers in this study was inadequate. The clothing worn by farmworkers in the study provided sufficient photoprotection, but removal of clothing during the day decreased its effectivity. The exposure of farmworkers to solar UVR exceeded the recommended CIE exposure limit during not only summer, but autumn and spring as well which indicates that photoprotective measures should not only be in use during summer but also during the other two seasons. The solar UVR exposure of the outdoor farmworkers included in our study was generally higher than the exposure of farmers and farmworkers in other countries. Finally, ten recommendations are made to the macadamia nut and avocado farm to reduce farmworkers’ exposure to solar UVR.