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Leslie London

Publications and source records attributed to Leslie London.

At least 19 recordsLinked to original sources

Toward a global agenda for research in environmental epidemiology.

The global environment is in critical decline. Whether one's concern about environmental epidemiology stems from the perspectives of environmental health, climate change, ecological collapse, or growing inequity, clear problems exist. Natural capital resources are being depleted; disregard for the integrity of ecosystems is entrenched in current business practices. Indeed, despite increasing rhetoric to the contrary, the disregard displayed by those who hold power globally toward long-term sustainability and, thus, the health and well-being of future generations, could be described as wanton. Six years ago, the Millennium Development Goals were announced by the United Nations as a rallying point for action to achieve a sustainable future, particularly by reducing the gap between the "have mores" and "have nots." The attainment of these Goals is now endangered, as is, apparently, the spirit of optimism and idealism that inspired them at the Millennium Summit. We call for a reinvigoration of both concern about-and action on-sustainability. In particular, we appeal to those engaged in the field of environmental epidemiology (and other specialties with whom they engage) to consider how they might help by incorporating sustainability issues (including global ecological integrity and global environmental justice) into their own research programs. This incorporation would make a vital contribution to protect both present and future generations and to reduce resource and health gaps between North and South. Simply put, we propose that sustainability becomes integral to advancing the science of environmental epidemiology and related environmental disciplines.

Conservation of Natural Resources↗

The impact of aerial application of organophosphates on the cholinesterase levels of rural residents in the Vaalharts district, Northern Cape Province, South Africa.

A cluster of Guillaine-Barre syndrome cases in the Vaalharts region, South Africa prompted an investigation of the impact of aerial organophosphate spraying on cholinesterase levels of residents in the region. A prospective study of cholinesterase levels among residents and workers in the area and a control area was performed. Standardized red blood cell cholinesterase levels amongst participants were monitored before (round 1), during (round 2), and after (round 3) the 1996/1997 aerial spraying season. Participants were assigned environmental exposure categories based on the time since (within 10 or 30 days) and distance from (on farm, on neighboring farm, <10 km from farm) aerial pesticide application. There were 342 participants in round 1, of whom 78% participated in round 2, 62% in round 3, and 56% in all three rounds. There was an increase in cholinesterase levels in round 2 (mean increase = 5.96+/-6.25 IU/g hemoglobin) and then a decrease in round 3 (6.17+/-6.51), significantly associated with environmental exposure (participants living on farm or neighboring farm and <10 km from spraying area) controlling for age, gender, alcohol dependence, and usual and recent domestic and occupational pesticide use (e.g., for round 2-round 1 cholinesterase differences, beta; (exposed group relative to unexposed)=5.72+/-1.21 IU/g hemoglobin, P = 0.000, R2 = 0.27, n = 171). The results show a shift in cholinesterase levels associated with residence in the spraying area, but in the direction opposite to that expected from the spraying of pesticides. Seasonal fluctuations in ambient temperature during the study may have influenced the results.

Adult↗

Disposal of unwanted pesticides in Stellenbosch, South Africa.

BACKGROUND: Unwanted pesticides in developing countries are major environmental health threats. This study followed-up a previous audit of unwanted and obsolete pesticides on farms in a rural district of South Africa six years after a National Retrieval Project (NPR) was undertaken. METHODS: A descriptive survey of 37 farms that had been in possession of unwanted pesticides in a 1995 survey and a purposive sample of 34 neighbouring farms, was carried out. The survey data included farm details; details of unwanted pesticide stocks, volumes of empty containers and safety and hygiene of pesticide stores. In addition, management was asked if they had been informed about and participated in the 1997 NPR and similarly whether they were aware of the retrieval planned by the African Stockpiles Programme (ASP). RESULTS: Forty (56%) farms were in possession of obsolete pesticides of which 24 (59%) were farms that had unwanted stocks in the previous survey. There were more than 9 tonnes of these pesticides, 50% more than in the previous survey, including 20 chemicals banned, withdrawn or restricted in South Africa or classified as WHO Class I toxicity. Over 2,800 kg of pesticides (30%) were not identifiable. None of the farms participated in the NPR, although 47 knew of the initiative. Only six farmers (9%) knew of the ASP initiative. Fifty-nine farms (83%) had empty containers on the premises. Most pesticide stores (67%) had floors contaminated with chemicals. CONCLUSION: The survey found that despite the NPR, the problem of unwanted pesticides in the study area and probably throughout South Africa has deteriorated. National and international policies should control the problem at source and encourage more sustainable agriculture.

Agriculture↗

Dual loyalties and the ethical and human rights obligations of occupational health professionals.

BACKGROUND: Underlying most ethical dilemmas in occupational health practice is the problem of Dual Loyalties where health professionals have simultaneous obligations, explicit or implicit, to a third party, usually a private employer. METHODS: A literature review was undertaken of case studies of workplace occupational health conflicts, international human rights and ethical codes and strategies for managing dual loyalties, complemented by iterative discussions in an international working group convened to address the problem of Dual Loyalties. RESULTS: Violations of the worker-patient's human rights may arise from: (1) the incompatibility of simultaneous obligations; (2) pressure on the professional from the third party; and (3) separation of the health professional's clinical role from that of a social agent. The practitioner's contractual relationship with the third party is often the underlying problem, being far more explicit than their moral obligation to patients, and encouraging a social identification at the expense of a practitioner's professional identity. CONCLUSIONS: Because existing ethical guidelines lack specificity on managing Dual Loyalties in occupational health, guidelines that draw on human rights standards have been developed by the working group. These guidelines propose standards for individual professional conduct and complementary institutional mechanisms to address the problem.

Conflict of Interest↗

Cost analysis of ELISA, solid-phase extraction, and solid-phase microextraction for the monitoring of pesticides in water.

The implementation of a pesticide water monitoring program in South Africa is limited by a lack of financial and analytical resources. A cost analysis of three analytical methods, enzyme-linked immunosorbent assays (ELISA), solid-phase microextraction (SPME), and traditional solid-phase extraction methods (SPE), was conducted. The cost analysis assumed a hypothetical scenario in terms of the sampling area (a grape farming rural region in the Western Cape province of South Africa), sample collection (weekly grab samples collected from eight sites by an environmental health officer in a nearby town), transport of samples (via courier), and analysis (endosulfan and chlorpyrifos analysis conducted by a local higher educational institution laboratory in Cape Town). The cost per sample for the three analytical methods was determined by estimating the annual capital costs, including building and equipment, and recurrent costs, including transport, personnel, supplies, and building operating costs. At the optimal utility of resources, SPME had the lowest cost per sample (US $37), followed by SPE (US $48.50) and ELISA (US $60). Recurrent costs formed the bulk of the costs of all three methods (91-97%). The cost of supplies was particularly high for ELISA (US $34 per sample). The cost per sample estimated for all three methods is substantially lower than those quoted by other laboratories in South Africa. The low cost of SPME is particularly important because of the sensitivity and reliability of this method and the faster output compared to SPE, and SPME is recommended for the long-term monitoring of pesticide pollution.

Chlorpyrifos↗

Reliability of a semi-quantitative method for dermal exposure assessment (DREAM).

Valid and reliable semi-quantitative dermal exposure assessment methods for epidemiological research and for occupational hygiene practice, applicable for different chemical agents, are practically nonexistent. The aim of this study was to assess the reliability of a recently developed semi-quantitative dermal exposure assessment method (DREAM) by (i) studying inter-observer agreement, (ii) assessing the effect of individual observers on dermal exposure estimates for different tasks, and (iii) comparing inter-observer agreement for ranking of body parts according to their exposure level. Four studies were performed in which a total of 29 observers (mainly occupational hygienists) were asked to fill in DREAM while performing side-by-side observations for different tasks, comprising dermal exposures to liquids, solids, and vapors. Intra-class correlation coefficients ranged from 0.68 to 0.87 for total dermal exposure estimates, indicating good to excellent inter-observer agreement. The effects of individual observers on task estimates were estimated using a linear mixed effect model with logged DREAM estimates as explanatory variable; "task", "company/department", and the interaction of "task" and "company/department" as fixed effects; and "observer" as a random effect. Geometric mean (GM) dermal exposure estimates for different tasks were estimated by taking the exponent of the predicted betas for the tasks. By taking the exponent of the predicted observer's intercept (exp(omega i)), a multiplier (M(O)) was estimated for each observer. The effects of individual observers on task estimates were relatively small, as the maximum predicted mean observers' multiplier was only a factor 2, while predicted GMs of dermal exposure estimates for tasks ranged from 0 to 1226, and none of the predicted individual observers' multipliers differed significantly from 1 (t-test alpha = 0.05). Inter-observer agreement for ranking of dermal exposure of nine body parts was moderate to good, as median values of Spearman correlation coefficients for pairs of observers ranged from 0.29 to 0.93. DREAM provides reproducible results for a broad range of tasks with dermal exposures to liquids, solids, as well as vapors. DREAM appears to offer a useful advance for estimations of dermal exposure both for epidemiological research and for occupational hygiene practice.

Administration, Cutaneous↗

Developing a competence framework and evaluation tool for primary care nursing in South Africa.

CONTEXT: Nurses provide the bulk of primary care services in South Africa. Post-apartheid health legislation envisions the provision of comprehensive primary services at all public clinics, which implies the need for a cadre of primary care nurses able to render such services. OBJECTIVES: To identify core competencies of clinic nurses and develop an evaluation tool for primary care nursing in South Africa. METHODS: The descriptive and exploratory techniques used included two meetings of a reference group of South African primary care professionals, followed by a consensus-building exercise. Using the Delphi technique expert opinion was solicited from South Africa, Canada and the USA. FINDINGS: The reference group meetings yielded a list of nine core competencies. Infrastructure issues, such as the supermarket (one-stop shopping) approach to service delivery, communication and transport systems, and the quality of supervision still cause concern. These issues underscore that competence cannot be measured in a vacuum. Input from Delphi participants affirmed the nine core competencies and the need to assess the impact of core competency training. One possible way to measure the nine core competencies would be to use proxy indicators. DISCUSSION/CONCLUSIONS: Identifying core competencies is a complex process. There is a need to process a wide range of views and ideas. Also, balancing academic concerns with service delivery needs and constraints is an ongoing challenge. A potential limitation of the Delphi technique is participant selection bias and fatigue. Accessing a diverse international panel and making numerous follow up attempts via phone, mail and email were used to attempt to ameliorate these inherent limitations. Although the process is cumbersome, providing "experts" with a venue to wrestle with these ideas can be fruitful. Future studies would help to assess the reliability of the findings.

Clinical Competence↗

Guillain-Barre syndrome in a rural farming district in South Africa: a possible relationship to environmental organophosphate exposure.

Although organophosphate (OP) insecticides have been recognized as having neuropathic potential, a relationship with Guillain-Barre syndrome (GBS) has not been previously confirmed. A cluster of 7 cases of GBS was noted over an 11-yr period in an isolated farming region in the Northern Cape Province of South Africa, an area subject to intensive aerial application of OP insecticides. Observed cases were more than 4 times higher than expected based on a Poisson probability distribution. Four cases were clustered in an area where the topography showed a marked hollow, and where spray drift of aerial OP insecticides was anticipated. The rate of GBS in this subcluster was more than 14 times higher than expected. The authors explored the hypothesis that aerial OP insecticide application was related to the raised incidence of GBS in this area and made suggestions for future research.

Adult↗

Contamination of rural surface and ground water by endosulfan in farming areas of the Western Cape, South Africa.

BACKGROUND: In South Africa there is little data on environmental pollution of rural water sources by agrochemicals. METHODS: This study investigated pesticide contamination of ground and surface water in three intensive agricultural areas in the Western Cape: the Hex River Valley, Grabouw and Piketberg. Monitoring for endosulfan and chlorpyrifos at low levels was conducted as well as screening for other pesticides. RESULTS: The quantification limit for endosulfan was 0.1 microg/L. Endosulfan was found to be widespread in ground water, surface water and drinking water. The contamination was mostly at low levels, but regularly exceeded the European Drinking Water Standard of 0.1 microg/L. The two most contaminated sites were a sub-surface drain in the Hex River Valley and a dam in Grabouw, with 0.83 +/- 1.0 microg/L (n = 21) and 3.16 +/- 3.5 microg/L (n = 13) average endosulfan levels respectively. Other pesticides including chlorpyrifos, azinphos-methyl, fenarimol, iprodione, deltamethrin, penconazole and prothiofos were detected. Endosulfan was most frequently detected in Grabouw (69%) followed by Hex River (46%) and Piketberg (39%). Detections were more frequent in surface water (47%) than in groundwater (32%) and coincided with irrigation, and to a lesser extent, to spraying and trigger rains. Total dietary endosulfan intake calculated from levels found in drinking water did not exceed the Joint WHO/FAO Meeting on Pesticide Residues (JMPR) criteria. CONCLUSION: The study has shown the need for monitoring of pesticide contamination in surface and groundwater, and the development of drinking water quality standards for specific pesticides in South Africa.

Agriculture↗

International law, human rights and HIV/AIDS.

This article explores the relevance of international human rights law in the response to the HIV/AIDS epidemic at national and international levels. Public health advocates can use arguments based on this body of law to promote responses to HIV/AIDS that reflect sound public health principles and documented best practice. Development assistance is increasingly linked to rights-based approaches, such as participatory processes, and strategic alliances between health professionals, organizations of people living with HIV/AIDS, and affected communities. Legal and human rights advocacy strategies are increasingly productive and necessary.

Acquired Immunodeficiency Syndrome↗

The nervous system effects of occupational exposure on workers in a South African manganese smelter.

Five hundred and nine production workers at a manganese (Mn) smelting works comprising eight production facilities and 67 external controls were studied cross-sectionally for Mn related neuroehavioural effects. Exposure measures from personal sampling included Mn in inhalable dust as cumulative exposure indices (CEI) and average intensity (INT). Biological exposure and biological effect measures included blood (MnB), urine (MnU) manganese and serum prolactin. Endpoints included items from the Swedish nervous system questionnaire (Q16), World Health Organisation neurobehavioural core test battery (WHO NCTB), Swedish performance evaluation system (SPES), Luria-Nebraska (LN), and Danish product development (DPD) test batteries, and a brief clinical examination. Potential confounders and effect modifiers included age, educational level, alcohol and tobacco consumption, neurotoxic exposures in previous work, past medical history, previous head injury and home language. Associations were evaluated by multiple linear and logistic regression modelling. Modelling assumptions were tested. Average exposure intensity across all jobs ranged from near 0 (0.06 microg/m3) for external controls to 5.08 mg/m3 for inhalable Mn, and was greater than the ACGIH TLV for 69% of subjects. Results from the large number of tests performed resolved into three groups. Group 1 shows differences between external unexposed referents and all the exposed and/or differences between internal low exposed referents and the rest of the exposed but no further exposure-response relationships. It includes the Santa Ana, Benton and digit-span tests from the WHO NCTB; the hand tapping and endurance tapping tests from the SPES; Luria-Nebraska item 2L; questionnaire items tired, depressed, irritated, having to take notes in order to remember things, and subjects' perception that they had sex less often than normal; a test of clinical abnormality; and increased sway under two conditions (eyes open without foot insulation, eyes open with foot insulation). Group 2 shows the presence of a more substantive exposure-response relationship. It consists of only two tests: and includes the WHO digit-symbol test (although the major impact is at low exposure and therefore counterintuitive, arguably placing this test in group 3) and the LN item 1R which has a step to a poorer score at high exposure. Group 3 contains the overwhelming majority of test results (almost all the questionnaire items, almost all the DPD tests including tremor, sway and diadochokinesia, and serum prolactin) which were either null or counterintuitive (did not make sense). The CEI was the strongest predictor of test abnormalities, except for the clinical test which was more strongly associated with blood manganese. Despite a comprehensive range of endpoints, and levels of exposure ranging from environmental to industrial, this large study of Mn workers found little convincing evidence for a continuum of effects, contributing further questions to current debates about the adequacy of the current ACGIH TLV.

Adult↗

The utility of biological monitoring for manganese in ferroalloy smelter workers in South Africa.

Five hundred and nine workers at a manganese (Mn) smelting works comprising eight production facilities and 67 external controls were studied cross-sectionally. Exposure measures from personal sampling included inhalable dust, cumulative exposure indices (CEI) and average intensity (INT = CEI/years exposed) calculated for the current job at the smelter and also across all jobs held by subjects. Biological exposure was measured by Mn in the blood (MnB) and urine (MnU) and biological effect was measured by serum prolactin. Average lifetime exposure intensity across all jobs ranged from near 0 (0.06 microg/m3) for unexposed external referents to 5 mg/m3. Atmospheric exposures and MnB and MnU distributions were consistent with published data for both unexposed and smelter workers. Associations between biological exposures and groups defined by atmospheric exposures in the current job were substantial for MnB, less so for MnU and absent for serum prolactin. Random sampling of MnB measurements representative of a group of workers with more than 1-2 years of service in the same job and notionally homogenous exposure conditions could serve as a cross-sectional predictor of atmospheric Mn exposure in the current job, as well as for surveillance of Mn exposure trends over time. Correlations at the individual level were only modest for MnB (33% of the variance in log atmospheric Mn intensity in the current job was explained by log MnB), much worse for MnU (only 7%). However, a receiver operating characteristic (ROC) analysis was performed which showed that it is possible to use a MnB cut-off of 10 microg/l (the 95th percentile in the unexposed) to good effect as a screening tool to discriminate between individual exposures exceeding and falling below a relatively strict atmospheric Mn exposure threshold at the ACGIH threshold limit value (TLV) of 0.2 mg/m3. MnU has no utility as a measure of biological exposure nor does serum prolactin as a measure of biological effect.

Alloys↗

Association between human paraoxonase gene polymorphism and chronic symptoms in pesticide-exposed workers.

Pesticides, such as parathion, are metabolized by cytochrome p-450 system to paraoxon, which is a potent cholinesterase inhibitor. Paraoxonase (PON) catalyzes the hydrolysis of these toxic metabolites and protects against pesticide toxicity. A glutamine/arginine (Gln/Arg) polymorphism at amino acid position 192 of PON has been described. The Arg/Arg genotype is associated with higher serum paraoxonase activity compared to Gln/Gln. The Arg/Gln genotype is associated with intermediate serum PON activity. The potential association between PON genotype and symptoms of chronic pesticide toxicity was examined among 100 farm workers. As part of a cross-sectional study of pesticide toxicity among mixed-race farm workers in the Western Cape. South Africa, 100 farm workers were genotyped for polymorphism of the paraoxonase gene at amino acid position 192. Subjects with two or more of the following symptoms were considered to have evidence of chronic toxicity: abdominal pain, nausea, rhinorrhea, dizziness, headache, somnolence, fatigue, gait disturbance, limb numbness, paresthesias, limb pain, or limb weakness. In multivariable logistic regression analysis, the independent predictors of chronic toxicity were previous history of head trauma resulting in loss of consciousness (OR 2.8, 95% CI = 1.7-6.7), having worked as a pesticide applicator (OR 5.4, 95% CI = 3.2-8.9), and having one of the two "slow metabolism" (Gln/Gln or Gln/Arg) genotypes (OR 2.9, 95% CI = 1.7-6.9). Furthermore, the prevalence of chronic toxicity increased in a stepwise fashion from 15% among pesticide nonapplicators with a "fast metabolism" (Arg/Arg) genotype, to 42.9% among pesticide nonapplicators with "slow metabolism" (Gln/Gln or Gln/Arg) genotypes, to 58.8% among pesticide applicators with "fast metabolism" genotype, and 75.0% among pesticide applicators with "slow metabolism" genotypes (P = 0.001). Age, number of years on the job, smoking history, alcohol history, education level, plasma or red blood cell cholinesterase level, or previous history of acute organophosphate poisoning were not statistically significant predictors of chronic toxicity. The PON genotype is an important determinant of a farmworker's susceptibility to chronic pesticide poisoning.

Adult↗