OpenUCT :: Browsing by Author "Todd, Gail"

Browsing by Author "Todd, Gail"

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Open Access
A study to characterise the “arsenic rash” observed at a copper smelter in Tsumeb, Namibia
(2022) Kew, Gregory Paul; Myers, Jonny; Todd, Gail
This study is located at a copper smelter. Arsenic is a component of copper bearing ore and arsenic trioxide is a by-product of copper smelting. The vapours (“off-gases”) that are released from the molten copper-bearing ore cool and condense in evaporative coolers to form arsenic-containing dust in the smelter's flues and stacks. The dust is filtered in “bag houses” and the captured powder is transported to Godfrey Roasters where the arsenic trioxide is driven off by heat. From there, the hot roaster gases are collected in what are known as “arsenic kitchens”, where fume is allowed to cool. The arsenic trioxide settles to the floor of the rooms as coarse dust and also forms crystalline deposits on the walls and ceilings. It is removed from the kitchens and prepared for shipment as a dust containing approximately 98% arsenic trioxide. Workers are exposed to arsenic containing dust during maintenance work on the copper smelter's flues and the bag houses, or whilst performing various tasks in the arsenic plant roasters and kitchens. The smelter has approximately 500 permanent employees and variable numbers of contractors, which can increase the total employee compliment by 1000. Skin rashes are the most common occupational disease reported at the copper smelter. The underlying cause of these acute transient rashes have historically been attributed by smelter employees to arsenic exposure, as encapsulated in the widely-used term, “arsenic rash”. Previous smelter reports have shown that the highest rates of skin rashes occurred at the arsenic plant and ausmelt baghouse. The appearance and anatomical distribution of the rash was described in these reports. Notwithstanding the use of the term, “arsenic rash”, the role of arsenic trioxide (As2O3) in the development of these rashes has been uncertain. In particular, a question has been raised as to whether the rash represents an allergy to either the arsenic trioxide or some other constituent of baghouse dust. Other uncertainties have related to the roles of skin hygiene practices and Personal Protective Equipment (PPE). This study included three levels of enquiry: a detailed questionnaire (exploring personal risk factors, skin hygiene practices, PPE use and descriptions of the rashes experienced); a clinical examination by a dermatologist; and skin patch testing (using both standard allergens as well as selected chemical agents from 4 selected workplaces, namely “pure” As2O3 powder from the arsenic plant, baghouse dust from the ausmelt & convertor plants, and “cake” from the Effluent Treatment Plant (“ETP”)). Analysis of the chemical compounds present in the four samples was performed by an external certified laboratory in Pretoria, South Africa. For the purposes of skin patch testing, all four samples were “standardised” to 2g/dL As2O3 in water by the Smelter's quality assurance lab. The epidemiological techniques varied according to the different objectives. For objectives 1 and 2: retrospective case control. For objective 3: exposure characterisation for use in exposure-response analysis. For objectives 4 & 5: retrospective case-control study, with controls matched for area of work in the smelter. Cases (N=27) comprised all employees who had one or more work-related rash incident within the preceding 12-24 months. These are relatively rare events, limiting the number of cases available for the study. Controls (N=24) comprised purposively selected co-workers, one control for each case, who performed the same type of work in the same workplace but who had never developed a rash. The principal variables included potential determinants of skin reactions to workplace materials (pure arsenic dust from the arsenic plant, baghouse dust from the ausmelt and converter and filter cake from the effluent treatment plant), reactions to patch testing, a history of allergy, prior experience of a similar rash, duration of service in the smelter and age. Ethical approval to conduct the study was obtained from the University of Cape Town's Health Research Ethics Committee (UCT HREC) (reference number 261/2016), and from the Office of the Permanent Secretary for Health, Namibia (letter dated 17 January 2018). Five study objectives were formulated, the outcomes of which are summarised as follows: Study objective 1: To interrogate if skin hygiene and hand cleansing practices used in the smelter, notably the use of barrier creams and soaps, are risk factors for developing a skin rash, and if so, at which anatomical location. The study data showed that hand washing practices of cases and controls were very similar, suggesting that handwashing practices are not a risk factor for developing a skin rash at any anatomical location, notably the hands. Furthermore, the data showed that the hand cream being issued as a barrier to chemical contact is not protective. However, both findings could be due to a non-differential bias whereby responses to the questionnaires in both groups of participants were influenced by a desire to appear compliant with company policy and conscientious with regard to cleanliness. Study objective 2: To interrogate the use of PPE by employees in the smelter, and whether or not this is a contributory factor to the development of the rash Whilst responses for the individual PPE related questions were generally similar in cases & controls, the combined prevalence of rashes in the area of the face (41%), respirator contact points (12.5%) and the neck area (19.6%) is high (73%). The rest of the body combined only accounts for 27%. Also, more specific questioning of the cases suggests that the respirators are a substantial contributor to the rashes in the face & neck areas. The lack of statistical significance between cases and controls for the individual PPE related questions could be due to the same non-differential bias operative in objective 1. Study objective 3(a & b): To characterise the nature of the chemical constituents in the production byproducts obtained from the various workplaces of the smelter operations (“workplace materials”). These “workplace materials” are the substances (usually in dust form) to which employees are exposed and which may trigger the skin reactions. The analysis addressed this in two ways; objective 3a looked at the chemical constituents of the workplace materials “as-is” (taken from the samples collected directly from the various workplaces as part of the smelter's Quality Assurance (QA) programme, and therefore as they are experienced by workers), and objective 3b looked at the chemical solutions used in the study skin tests, after standardisation for arsenic trioxide at 2g of arsenic trioxide per 100mL of water. Objective 3a: The proportionate concentrations of As2O3 varied from 5% to 98% across the 4 samples from the 4 workplace locations, namely the arsenic plant (98%), ausmelt baghouse (83%), convertor baghouse (21%) and ETP (5%). Lead and sulphur were identified as additional potential irritants in the convertor baghouse dust and the ETP cake. Both baghouse dusts (ausmelt & converter) had alkaline pH, the As2O3 sample from the arsenic plant had an acid pH and the pH of the ETP sample was close to neutral. Objective 3b: The samples were standardised to 2g/dL As2O3 in water, to better ascertain the skin responses to arsenic trioxide specifically at varying dilutions. This concentration was chosen because it is the point of solubility of arsenic trioxide in water. Consequently, the two samples with relatively lower As2O3 in the source material (converter Baghouse dust & ETP cake) had proportionately increased concentrations of their non-arsenic constituents after standardisation. These proportionate increases were 19% (ausmelt baghouse), 373% (converter baghouse) and 1799% (ETP). Should any of the non-arsenic constituents be irritants, their irritancies would be equivalently affected. Following standardisation for arsenic, the pH for the ausmelt sample went up from pH 7.8 to pH 8.8, the converter sample went from pH 8.7 to pH 9.6 and the ETP sample went from pH 6.7 to 7.8. The arsenic plant sample had a pH of 4.5 after standardisation. Unfortunately, the smelter lab did not provide a pH of the pre-standardised arsenic plant sample. The high pH levels (8.8 & 9.6) or low pH level (4.5) are independently capable of causing irritation. Study objective 4: To characterise the nature of the dermatological response to these exposures, notably whether the reactions are allergic or irritant in nature. The main finding of this study is that arsenic trioxide is an irritant not an allergen, because of its low pH as well as an inherent dermal toxicity. The grounds for this conclusion are (1) the clinical appearance of the skin reactions where arsenic trioxide was in contact with the skin and (2) the dose-response relationship with increased concentrations of arsenic trioxide with the skin. The presence of arsenic trioxide in the baghouse dust and ETP cake confers irritant properties to these operational materials. The baghouse dusts are additionally irritant because of their high pH. The ETP cake produced a dosedependent irritant reaction even though it was pH neutral. Irritancy has implications on exposure prevention, in that all employees are potentially affected, not only a subset of vulnerable people. Study objective 5: To try to ascertain any causal relationship between baghouse dust (and notably the As2O3 in the dust) and the pathological outcomes The irritancy of arsenic trioxide in the arsenic plant sample was clearly demonstrable even though it was significantly diluted during the standardisation process (to 2g/dL). Arsenic plant workers in the realworld setting are exposed to undiluted concentrations of arsenic trioxide dust, which explains the high prevalence of irritant skin reactions amongst workers in this area. This study has demonstrated that the alkaline pH of baghouse dust confers additional irritancy to that already conferred by the arsenic trioxide present in the dust. This explains the high prevalence of irritant skin reactions amongst workers exposed to baghouse dust. This report ends with some recommendations, based on the findings of the study, as well as knowledge gaps identified.
Open Access
An in vitro study of neutrophil chemotaxis
(1976) Todd, Gail; Dowdle, E B
When, at the beginning of 1972, my scientific attention was first drawn to the subject of cellular participation in the inflanunatory response, I was struck by the need for an understanding of the cellular and molecular mechanisms whereby blood leucocytes are attracted to an area of injury. The literature at that time contained good technical accounts of methods available for studying chemotaxis in vitro and many reports of diverse compounds of biological origin with attractant, or chemotactic, properties for motile, phagocytic cells. In general, these reports tended to substantiate the belief that chemical substances generated at an inflannnatory source attracted cells to that source in a teleologically appropriate way and they justified, by the consistent correlation observed, the relevance of in vitro procedures for studying the phenomenon. In other words, answers were available to the question "What substances attract?"; very few were available to the question, "How do they attract?".
Open Access
The diffusion of the internet amongst South African primary care doctors : an activity systems view
(2009) Masters, Kenneth Andrew; Ng'ambi, Dick; Todd, Gail
Includes abstract. Includes bibliographical references (p. 379-436). Has accompanying material on CD.
Open Access
Genomics study of anti-tuberculosis drug-induced hypersensitivity reactions
(2015) Shebe, Khadija Ahmed; Lehloenya, Rannakoe J; Todd, Gail
Introduction: All first-line anti-tuberculosis drugs can be associated with all phenotypes of cutaneous adverse drug reactions (CADR). Second-line drugs are associated with much poorer outcomes. Thus, identifying the offending drug in poly-pharmacy is difficult. Re -challenge with the drug is the gold standard in identifying the offender, however poses unacceptably high risk of CADR recurrence. Population and drug-specific genomics help identify those susceptible to adverse reactions to a drug facilitating avoidance of the drug. Objective: To investigate the genomic susceptibility in patients with confirmed rifampicin and or isoniazid-associated hypersensitivity reactions using both genome- wide association studies and candidate gene approaches. Methods: A case control study using 14 patients with previous tuberculosis-associated CADR who were re-challenged with first-line anti-tuberculosis drugs and subsequently developed re-challenge reactions to either isoniazid or rifampicin as cases. These were compared with 30 controls who had tolerated rifampicin and isoniazid during the re- challenge process (12 patients, Group 1a) and consecutive patients who had been on TB treatment for at least 12 weeks without developing any adverse drug reaction (1 8 patients, Group 1b) and 200 black South Africans from the general population. HLA genotypes of the samples were determined by SeCore® HLA Sequence based typing (Invitrogen, Life technologies, USA), and potential ambiguities were resolved by sequencing-based typing. Results: We found HLA-B*58:02 (OR=3.6; 95% CI: 1.4-8.99) and HLA-DRB1*09:01 (OR=15.3; 95% CI: 2.1-113.1) to be significantly more prevalent in patients who developed rifampicin and isoniazid-associated CADR as compared to black South African general population. However, we found no significant associations between HLA genotype and rifampicin/isoniazid-associated CADR when we compared the cases to our study controls that had tolerated rifampicin and isoniazid. HLA-B *58.02 was not found to be statistically associated with HIV positive status (p=0.42) and DRESS phenotype ( p= 0.6279). The majority of our cases were black Africans. Approximately 80% of our cases and controls were HIV-infected. DRESS/DIHS was the prevalent phenotype of CADR, accounting for approximately 80% of cases and controls. Discussion: To our knowledge, this is the first study to show an association between HLA-B*58:02 and HLA-DRB1*09:01 alleles and severe cutaneous adverse drugs reactions secondary to rifampicin and isoniazid in an African population. We identify 2 candidate HLA alleles that need confirmation of their association in African patients who develop rifampicin or isoniazid-associated CADR in larger studies. The value of identifying candidate alleles could lead to CADR preventative screening prior to initiating anti-tuberculosis therapy in black South Africans. The HLA-B*58:02 noted in our cases and controls tolerant of the drugs might not be associated with CADR but could be a reflection of the HIV status and control in HIV-TB co-infected persons. Conclusion: HLA-B*58:02 and HLA-DRB1*09:01 may be associated with rifampicin and isoniazid-associated CADR. Alternately HLA-B*58:02 may be associated with HIV status rather than CADR. A sufficiently powered study is needed to confirm this association.
Open Access
I found it on the internet preparing for the e-patient in Oman
(Sultan Qaboos University, 2010) Masters, Ken; Ng'ambi, Dick; Todd, Gail
In the Information Age, the communication patterns between doctor and patient are changing. Using Everett Rogers' theory of Diffusion of Innovations, this paper begins by examining the diffusion of the Internet in the world and in Oman. It then considers the emergence of e-patients. The characteristics of e-patients are described in some detail. The paper ends by describing steps that should be taken when teaching medical students in Oman so that they can be prepared for e-patients.
Open Access
Kaposi's sarcoma: Genetic subtypes and clinical correlation in a South African population
(2017) Isaacs, Thuraya; Todd, Gail; Katz, Arieh A
Human herpes virus 8 (HHV8) is the aetiological agent of all forms of Kaposi's sarcoma (KS). Seven major subtypes (A, B, C, D, E, F, Z) based on genetic variability of open reading frame (ORF)-K1, have been identified. Numerous studies point to differing tumorigenic and pathogenic properties of the HHV8 subtypes. The study objective was to determine the prevalence of the HHV8 subtypes in a cohort of clinical and histologically confirmed KS in Cape Town, South Africa, and analyse associations between the different subtypes, clinico- epidemiological forms and clinical presentation of KS. The clinical data was prospectively collected and recorded on a body diagram and with photographs. Demographic data was retrospectively collected from clinical records. Tissue biopsies were taken for ORF-K1 subtyping. Out of a cohort of 103, eighty six patients were subtyped; 81 AIDS (aquired immune deficiency syndrome)-KS and 5 African endemic. Subtype A5 (42/86) and B2 (16/86) predominated. B1, B3, A1 and A4 subtypes were identified in 10/86, 9/86, 4/86 and 1/86 patients respectively. A5, B1, B2 and B3 were found in African blacks and individuals of mixed ancestry, while subtypes A1 and A4 are found only in whites and individuals of mixed ancestry. Subtype A5 was associated with >10 KS lesions at presentation in the AIDS-cohort (32/38, p=0,050), but not in the African endemic patients (2/4, p=0,600). Subtypes A1 and A4 were less likely to be associated with poor risk tumour extension (p=0,031) and A1 was associated with lower likelihood of lower limb involvement (p=0,004).
Restricted
Lettuce allergy: allergies in the workplace
(2005) Gottschalk, Gavin; Todd, Gail
A casual worker in a vegetable-packing plant developed hand and forearm eczema soon after commencing work in the lettuce-packing section. Despite a negative standard battery, targeted patch testing revealed lettuce as the offending agent; this highlights the need to use the patient's own materials identified from an appropriate risk assessment of the workplace in cases of suspected allergy. Development of her eczema may have been facilitated by chronic exposure to water, emphasizing the need for workers to have access to gloves, and education about their correct use.
Open Access
Predictors of occupational skin disease among seafood processing workers in the Western Cape
(2012) Burdzik, Amy; Jeebhay, Mohamed; Todd, Gail
Occupational skin disease is common in seafood processing workers. While previous studies have reported an increased prevalence of symptoms (as high as 50%) and protein contact dermatitis (3-11%), the prevalence and patterns of type IV allergic contact dermatitis have not been well characterised in epidemiological studies. The aim of this study was to identify host and environmental risk factors for symptoms, clinical eczema, positive patch tests, possible and probable allergic contact dermatitis in seafood processing workers. A cross-sectional study of 594 seafood processing workers was conducted in two seafood processing plants in the Western Cape Province of South Africa. The study used an interviewer administered questionnaire to collect information on demographic characteristics, occupational history, work practices and skin symptoms in the preceding 12 months. A subgroup of symptomatic workers (n=120) were investigated further and compared to a group of randomly selected asymptomatic workers (n=134). Both groups underwent clinical examination by experienced dermatologists and patch testing with a battery of standard allergens (adapted British Contact Dermatitis Group Standard Series) supplemented by various seafood products and additives used in the factory. Data of skin prick tests to common aeroallergens and seafood products, and serum omega-3 fatty acid (Eicosopentaenoic acid) collected in a previously reported study were also used.
Open Access
Relevance of a positive latex specific IgE result in a non medical occupational setting
(2011) Motsepe, Didintle Christine; Todd, Gail
Background: In 2007, three patients from Impregnated Web Technology (IWT) factory were referred to Groote Schuur occupational clinic with contact dermatitis. The IWT factory manufactures sanding and grinding discs, traditionally a low latex exposure industry. Workers at this factory were introduced to latex gloves in 2004 to protect their hands for various reasons. One of the patient was referred with raised latex specific IgE. Our preliminary diagnosis was irritant contact dermatitis. The dermatitis cleared after avoiding latex gloves. The other two were referred with negative latex specific IgE. One was subsequently diagnosed of fiberglass dermatitis confirmed with histology and the other with urticaria based on the history. Because of the perception that skin problems equate to latex allergy we decided to study the relevance of a positive latex specific IgE in a nonmedical setting. Objective: The objective of this study is to determine the prevalence and relevance of latex sensitization at this traditionally a low latex exposure factory. It also aimed to increase awareness of latex exposure and provide recommendations for preventing and managing latex allergies. Methods: A cross sectional study of the workers on duty was conducted at the IWT factory over 2 days. There were no exclusion criteria. Ethics approval was obtained. Workers who volunteered were asked to sign informed consent and answer 3 questionnaires. Questioned asked were related to glove use at work and at home. They were also examined by the investigator and had a blood sample taken for total IgE and latex specific IgE measurement. Results: There were 160 workers on the factory floor over the study period. Only 81 workers volunteered giving a response rate of 51 %. The point prevalence of latex sensitization was 16 %(13/81). There was a significant relationship between workers who had skin signs and wore glove, however there was no association between glove usage and total and latex specific IgE. A raised latex specific IgE was associated with permanent employment. Conclusion: The prevalence of elevated latex specific IgE amongst workers at IWT factory was high, in the range of that reported of medical personnel, suggesting a source of latex exposure in the work place. The reasons for glove use amongst the workers revealed an appropriate use of natural rubber latex gloves with unnecessary latex exposure. Although we could not link the high prevalence of latex specific IgE to the use of gloves, subgroup analysis with larger numbers of workers may expose an association suggested by a higher prevalence in permanent workers. We suggest the use of more appropriate gloves selected for the protection needed. A latex specific IgE test should be performed only for workers with strong suspicion of latex sensitization, not simply skin signs and symptoms.
Open Access
Stevens Johnson Syndrome and toxic epidermal necrolysis: maternal and foetal outcomes in twenty-two consecutive pregnant HIV infected women
(Public Library of Science, 2015) Knight, Lauren; Todd, Gail; Muloiwa, Rudzani; Matjila, Mushi; Lehloenya, Rannakoe J
Introduction Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) form a spectrum of a rare and life-threatening cutaneous drug reaction. SJS/TEN in pregnancy poses largely unknown risk factors and outcomes for both the mother and foetus compared to the general population. METHODS: We conducted a study of consecutive pregnant women admitted to single tertiary referral centre in South Africa with SJS/TEN over a 3 year period. They were all managed by the same medical team using the same protocols. We evaluated their underlying illnesses, offending drugs and the course of pregnancy and outcomes to determine factors influencing maternal and foetal outcomes. RESULTS: We identified twenty-two women who developed SJS/TEN while pregnant, all of them HIV-infected. Their median age was 29 years. The majority 16/22 (73%) had SJS, the milder variant of the disease affecting < 10% body surface area. Nevirapine was the offending drug in 21/22 (95%) cases. All 22 of the mothers survived with 3/22 (14%) developing postpartum sepsis. Pregnancy outcomes were known in 18/22 women and 9/18 (50%) babies were delivered by caesarean section. There were 2 foetal deaths at 21 and 31 weeks respectively and both were associated with post-partum sepsis. Postnatal complications occurred in 5 cases, 3 involving the respiratory system and the other two being low birth weight deliveries. Eight placentae and one foetus were sent for histology and none showed macroscopic or microscopic features of SJS/TEN. On follow-up, only 12/20 children were tested for HIV at 6 weeks post-delivery and none of them were HIV-infected. All had received prophylactic ARVs including nevirapine. CONCLUSIONS: TEN, the severe form of the disease, was associated with poorer foetal outcomes. SJS/TEN-associated mortality is not increased in HIV-infected pregnant women. Maternal SJS/TEN does not seem to commonly manifest in the foetus.
Open Access
Validation of the United Kingdom Working Party diagnostic criteria for atopic eczema in an African setting
(2005) Chalmers, Debra; Ehrlich, Rodney; Todd, Gail
Objectives: to determine the prevalence of atopic eczema in a Southern African setting using both a modified version of the UK working party diagnostic criteria for atopic eczema and a clinical assessment by a dermatologist, and to measure the validity of the UK criteria.

Browsing by Author "Todd, Gail"

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