Browsing by Author "Holtman, Zelda"

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    Genetic polymorphisms and organophosphate neurotoxicity amongst emerging farmers in the Western Cape
    (2016) Glass, Tracy; Dalvie, Mohamed Aqiel; Holtman, Zelda; Ramesar, Raj
    BACKGROUND: Long-term exposure to organophosphates (OPs) can cause chronic neurotoxic effects which may be modulated by genetic polymorphisms of xenobiotic metabolising enzymes (XMEs). No previous study investigated XME modulation of neurotoxicity outcomes. OBJECTIVES: To investigate whether XMEs polymorphisms modulate OP neurotoxicity among emerging farmers. METHODS: A cross-sectional study of 301 emerging farmers was conducted in the rural Western Cape of South Africa. Neurotoxicity testing included the World Health Organisation Core Test Battery (digit span forward and backward) and vibration sensitivity testing. Questionnaire items included demographic data, potential confounders and work history of pesticide exposures. Blood samples were analysed for genetic polymorphisms of the following XMEs; glutathione S-transferases (GST), N-acetyltransferases (NAT) and Paraoxonase (PON1). RESULTS: Median age was 39 (30-48) and most had 9 years of education or less (65.5%). 54% of the participants were OP pesticide applicators. There was a low prevalence of the GST null genotype (GSTT-1% and GSTM-16%) and the GA and GG genotype for NAT (10%). Modulation of OP exposure and neurotoxic outcome relationships by NAT, PON1 at position 192 and GST was indicated in multivariate analysis. The strongest evidence of modification was by NAT on the relationship between pesticide poisoning and impaired vibration sense. Poisoned individuals with the GG genotype were more likely to suffer from impaired vibration sense compared to GA and AA genotypes. CONCLUSION: Genetic polymorphisms of NAT, PON1 (at position 192) and GSTM may modify the relationship between OP exposure and neurotoxicity. Larger longitudinal studies are required to determine whether preventive strategies can be developed to improve health amongst the identified vulnerable groups.
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    Neurobehavioural effects of pesticide exposure among emerging farmers in the Western Cape
    (2013) Holtman, Zelda; London, Leslie; Dalvie, Mohamed Aqiel
    The number of emerging farmers is increasing in South Africa. This study investigated neurotoxic effects resulting from long-term low-level exposure to organophosphate pesticides amongst emerging farmers. A cohort study involving 319 (66% male and 34% female) emerging farmers in the Western Cape was conducted between 2009 and 2010. Testing included a questionnaire exploring demographic details, work history, medical history; the Q16 and the Brief Symptom Inventory (BSI). Additionally, neurobehavioural performance was assessed on the following: Digit span forward and backward, Digit Symbol, Santa Ana Pegboard, Pursuit Aiming, Benton Visual Retention and Vibration sense as measured by vibration sense threshold using a 256 Hz frequency tuning fork. Exposure to OP's was derived from three metrics: (i) OP applicator status, (ii) cumulative OP exposure weighted for task/activity, (iii) diagnosed past poisoning. Two sets of analyses were conducted: a cross-sectional analysis at baseline (N=319), and a cohort analysis (N=273), comparing change in neurobehavioural performance over the 12 month follow up period. The exposure variable for cumulative occupational OP exposure in the baseline cross-section was generated from the job history data in the farmer questionnaire based on the exposure obtained during the current job and preceding three jobs. This represented long-term past OP exposure. In both the baseline cross-section and the cohort analysis, the relationship investigated was between dichotomised outcomes and four models for OP exposure. Three models used each of the metrics for OP exposure and a fourth model used the metric of cumulative OP exposure adjusted for diagnosed past poisoning. The difference between the analysis in the cohort was that both cumulative exposure and acute poisoning were restricted to the 12 months of follow up, whereas the baseline, both cumulative and acute poisoning were based on any past exposure without a time period. Further, for the cohort study (n=273), the outcomes were the difference in scores (measured as the ratio of the repeat measure at one year to the baseline score) which were regressed in the four exposure models outlined above. All models were controlled for confounders including age, gender, schooling, language, current alcohol consumption, previous head injuries, psychological illness and socioeconomic status. Model building led to the inclusion of additional co-variates for some of the analyses.
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    Pesticide Research on Environmental and Human Exposure and Risks in Sub-Saharan Africa: A Systematic Literature Review
    (Multidisciplinary Digital Publishing Institute, 2021-12-27) Fuhrimann, Samuel; Wan, Chenjie; Blouzard, Elodie; Veludo, Adriana; Holtman, Zelda; Chetty-Mhlanga, Shala; Dalvie, Mohamed Aqiel; Atuhaire, Aggrey; Kromhout, Hans; Röösli, Martin; Rother, Hanna-Andrea
    On the African continent, ongoing agriculture intensification is accompanied by the increasing use of pesticides, associated with environmental and public health concerns. Using a systematic literature review, we aimed to map current geographical research hotspots and gaps around environmental and public health risks research of agriculture pesticides in Sub-Saharan Africa (SSA). Studies were included that collected primary data on past and current-used agricultural pesticides and assessed their environmental occurrence, related knowledge, attitude and practice, human exposure, and environmental or public health risks between 2006 and 2021. We identified 391 articles covering 469 study sites in 37 countries in SSA. Five geographical research hotspots were identified: two in South Africa, two in East Africa, and one in West Africa. Despite its ban for agricultural use, organochlorine was the most studied pesticide group (60%; 86% of studies included DDT). Current-used pesticides in agriculture were studied in 54% of the study sites (including insecticides (92%), herbicides (44%), and fungicides (35%)). Environmental samples were collected in 67% of the studies (e.g., water, aquatic species, sediment, agricultural produce, and air). In 38% of the studies, human subjects were investigated. Only few studies had a longitudinal design or assessed pesticide’s environmental risks; human biomarkers; dose-response in human subjects, including children and women; and interventions to reduce pesticide exposure. We established a research database that can help stakeholders to address research gaps, foster research collaboration between environmental and health dimensions, and work towards sustainable and safe agriculture systems in SSA.
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    Prejudice and social contact in South Africa: A study of integrated schools ten years after apartheid
    (2005) Holtman, Zelda; Louw, Johann; Tredoux, Colin; Carney, Tara
    In this article the relationship between intergroup contact and racial prejudice in formerly segregated schools in Cape Town, South Africa, is investigated. A total of 1 119 black African, coloured, Afrikaans-speaking and English-speaking white learners were surveyed, using three measures of intergroup prejudice, a self-report intergroup contact measure and a racial identifi cation scale. In general, quality of contact with individuals of other race groups and an increase in contact both in and outside of the school improved learners’ race attitudes. Higher levels of demographic integration within schools were also positively related to race attitudes, but a high degree of identifi cation with one’s own race led in several instances to less positive attitudes towards other race groups. Intergroup contact seemed to be the single most important predictor of attitudes for all four groups in this study