Faculty of Health Sciences
School of Health Systems and Public Health
School of Health Systems and Public Health
Selected Highlights from Research Findings
It is widely believed that cancer can be prevented by high intake of fruits and vegetables. However, inconsistent results from many studies have not been able to conclusively establish an inverse association between fruit and vegetable intake and overall cancer risk.
We conducted a prospective analysis of the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort to assess relationships between intake of total fruits, total vegetables, and total fruits and vegetables combined and cancer risk during 1992–2000. The EPIC study is a multicenter conducted in 10 Western European countries with a great variability in fruit and vegetable intake between different populations. Detailed information on the dietary habit and lifestyle variables of the cohort was obtained. Cancer incidence and mortality data were ascertained, and hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using multivariable Cox regression models. Analyses were also conducted for cancers associated with tobacco and alcohol after stratification for tobacco smoking and alcohol drinking.
Of the initial 142 605 men and 335 873 women included in the study, 9604 men and 21 000 women were identified with cancer after a median follow-up of 8.7 years. The crude cancer incidence rates were 7.9 per 1000 person-years in men and 7.1 per 1000 person-years in women. Associations between reduced cancer risk and increased intake of total fruits and vegetables combined and total vegetables for the entire cohort were similar (200 g/d increased intake of fruits and vegetables combined, HR = 0.97, 95% CI = 0.96 to 0.99; 100 g/d increased intake of total vegetables, HR = 0.98, 95% CI = 0.97 to 0.99); intake of fruits showed a weaker inverse association (100 g/d increased intake of total fruits, HR = 0.99, 95% CI = 0.98 to 1.00). The reduced risk of cancer associated with high vegetable intake was restricted to women (HR = 0.98, 95% CI = 0.97 to 0.99). Stratification by alcohol intake suggested a stronger reduction in risk in heavy drinkers and was confined to cancers caused by smoking and alcohol.
A very small inverse association between intake of total fruits and vegetables and cancer risk was observed in this study. Given the small magnitude of the observed associations, caution should be applied in their interpretation.
Contact person: Dr J Wichmann.
Since 2008 the Department of Family Medicine and the School of Health Systems and Public Health have worked on transforming a didactic, large class module to an academic service learning module. In the health sciences, the conceptual model of academic service learning - which includes specific learning objectives (such as social responsibility or civic learning) – is easily confused with service delivery. Every two years this module is intensively evaluated and the results have been shared in academic work such as conference presentations, posters and a book chapter. In essence the module has transformed the perceptions of students, enhanced their learning in meaningful ways as well as providing opportunities for students to exercise their sense of agency in responding to the broader needs of the society in which they serve. Academic staff have similarly deepened and broadened their understanding of the field of study, the needs of students and can account for their practice.
This module provides ample proof that community-based education is a richer, more meaningful experience for both students and staff.
Contact person: Mrs JE Wolvaardt.
In developed nations people spend about 90% of their time indoors. The relationship between indoor and outdoor air pollution levels is important for the understanding of the health effects of outdoor air pollution. Although other studies describe both the outdoor and indoor atmospheric environment, few excluded a priori major indoor sources, measured the air exchange rate, included more than one microenvironment and included the presence of human activity.
PM2.5 (particulate matter smaller than 2.5 µm in diameter), soot, NO2 (nitrogen dioxide) and the air exchange rate were measured during winter and summer indoors and outdoors at 18 homes (mostly apartments) of 18 children (6-11 years old) and also at the six schools and 10 pre-schools that the children attended. The measurements were conducted during 1 December 2003 and 1 July 2004. The three types of indoor environments were free of environmental tobacco smoke and gas appliances, as the aim was to asses to what extent PM2.5, soot and NO2 infiltrate from outdoors to indoors. The median indoor and outdoor PM2.5 levels were 8.4 mg.m-3 and 9.3 mg.m-3, respectively. The median indoor levels for soot and NO2 were 0.66 m-1 x 10-5 and 10.0 mg.m-3, respectively. The respective outdoor levels were 0.96 m-1 x 10-5 and 12.4 mg.m-3. The median indoor/outdoor (I/O) ratios were 0.93, 0.76 and 0.92 for PM2.5, soot and NO2, respectively. Their infiltration factors were influenced by the micro-environment, ventilation type and air exchange rate, with aggregated values of 0.25, 0.55 and 0.64, respectively. Indoor and outdoor NO2 levels were strongly associated (R2 = 0.71), followed by soot (R2 = 0.50) and PM2.5 (R2 = 0.16).
In Stockholm, the three major indoor environments occupied by children offer little protection against combustion-related particles and gases in the outdoor air. Outdoor PM2.5 seems to infiltrate less, but indoor sources compensate.
Contact person: Dr J Wichmann.
Dr. Mutero’s career spans more than 25 years of professional engagement in research and capacity-building for the control of malaria and other vector-borne diseases in Africa. He is currently a senior researcher and visiting lecturer in environmental and occupational health at University of Pretoria’s School of Health Systems and Public Health. He is a co-principal investigator and regional coordinator of a GEF/UNEP/WHO-funded project on malaria control policy- making in Kenya, Uganda and Tanzania. From 2001-2006 he was the founding Coordinator of the System-wide Initiative on Malaria and Agriculture (SIMA) based at the International Water Management Institute (IWMI). SIMA was an inter-Centres research initiative of the Consultative Group on International Agricultural Research (CGIAR), supported by World Bank, International Development Research Centre (IDRC), Dutch Government and African Development Bank. SIMA projects used trans-disciplinary and participatory research as a basis for holistic understanding of complex linkages between socio-ecological systems and human health. Through SIMA, Dr. Mutero coordinated the implementation of projects in Kenya, Uganda, Tanzania, Ghana, Ethiopia, Mozambique and Zimbabwe. Prior to joining IWMI, he worked as a medical entomology research scientist for more than 15 years - at the International Centre of Insect Physiology and Ecology (ICIPE) in Nairobi, Kenya. He is a senior associate in health policy research with the Africa Policy Institute (API), and serves as a consultant to World Health Organization (WHO) and RTI International/USAID on integrated vector management (IVM). He has widely published his research in internationally peer-reviewed journals.
Contact person: Dr CM Mutero.
For malaria vector control DDT has been shown to be effective, however the effects of DDT on human health emphasizes the need for better safer alternatives. DDT has negative effects on seminal parameters and the hormone system of rural males from a malaria area in the Limpopo Province, South Africa (Aneck-Hahn et al., 2007; de Jager et al., 2009).
The use of pyrethroids although not ideal is an alternative. In South Africa alpha-cypermethrin is one of the pyrethroids use for malaria vector control in the Limpopo Province and also on agricultural crops for pesticide control in order to replace the use of organophospates (OP’s). Exposure to pyrethroids appears to be multi-media and multi-route using exposure biomarkers will be useful in human epidemiological studies. Animal and in vitro studies have suggested that some pyrethroids and metabolites have endocrine disrupting properties. Several human studies have suggested that occupational exposure to pyrethroids have resulted in reduced semen quality and increased DNA damage and chromosomal defects in sperm.
The results from a pilot study in a control area where DDT is not used showed participants had sub-normal seminal characteristics. The aim of this MRC funded study which will run over a period of three years will be to investigate the exposure levels of participants from the DDT and the reference population to other active ingredients, like pyrethroid insecticides and OP’s.
In light of the previous study on non-occupational exposure to DDT and its metabolites this study will expand our knowledge of possible additive or synergistic effects of OP’s and pyrethroid insecticide exposure on male reproductive health in an already vulnerable population.
Contact person: Prof C de Jager.
The presence of estrogenic compounds in drinking, source and waste waters is of international concern because of the potential adverse effects on wildlife and humans. Chemical analysis alone is difficult due to the low environmental levels of the chemicals and usually mixtures of chemicals are present. Biological methods are becoming more popular as screening tools as they are able to assess the total activity present in the sample. However no single assay can accurately predict the total estrogenic activity and therefore a recommended suite of assays was developed that are suitable, reliable and available in South Africa.
The WRC mandated the SHSPH to develop one of the five user friendly training manuals, specifically focussing on sampling, biological and analytical procedures. A consensus workshop was held in 2009 where the bioassays relevant to South Africa were selected with the aim to standardize the methodology for sample preparation, methods and calculations. The manual was completed and submitted to the WRC in March 2010.
Contact person: Prof C de Jager.
Endocrine disruptive chemical (EDC) activity and health effects of identified Veterinary compounds in surface and ground water (WRC project: K5-1686)
Endocrine disrupting chemicals (EDCs) are present in mixtures in the environment and may have adverse effects on animal and human health. In South Africa (SA) 75% of all bovine produced stems from the feedlot production system. Recent studies have revealed the presence of androgenic and estrogenic active metabolites in the water effluent from cattle feedlots. These active metabolites are steroids used in the meat industry as growth stimulants to increase growth performance of cattle.
This project, a first of its kind in South Africa initiated by Prof C de Jager (SHSPH) was a multi-institutional project funded by the Water Research Commission (WRC) of South Africa. It consisted of a pilot study and a main study made up with a number of interlinked phases. The Pilot study and Phase 1-3 took place from 2006-2008. Phase 4 (SHSPH, UP) was the reproductive toxicology study in rats using the identified mixtures of veterinary compounds identified from Phase 1.
The aim of Phase 4 was to determine the effects of selected veterinary growth stimulants (GS) used at cattle feedlots on male reproductive health, using Sprague Dawley rats. The rats were exposed to environmentally relevant concentrations of mixtures with estrogenic (zilpaterol, diethylstilbestrol (DES) and a-zearalanol), androgenic (ß-trenbolone and methyltestosterone) -activity and a combination group. A control group was also included in the experimental procedure. The study investigated the endocrine disrupting effects of maternally exposed rats (P1) to selected veterinary growth stimulants on the fertility and reproductive parameters in lifetime exposed F1 males. The findings indicated that exposure to environmentally relevant concentrations of veterinary growth stimulants had an effect on the reproductive health of maternally and direct exposed male rats. This might have serious implications for human reproductive health.
The results of all the phases were submitted to the WRC as a final report in March 2010.
Contact person: Prof C de Jager.
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