Natural radioactivity levels in soils, rocks and water at a mining concession of Perseus gold mine and surrounding towns in Central Region of Ghana.

Levels of naturally occurring radioactive materials prior to processing of gold ore within and around the new eastern concession area of Perseus Mining (Ghana) Limited were carried out to ascertain the baseline radioactivity levels. The study was based on situ measurements of external gamma dose rate at 1 m above ground level as well as laboratory analysis by direct gamma spectrometry to quantify the radionuclides of interest namely; (238)U, (232)Th and (40)K in soil, rock, ore samples and gross alpha/beta analysis in water samples. The average absorbed dose rate in air at 1 m above sampling point using a radiation survey metre was determined to be 0.08 ± 0.02 µGyh(-1) with a corresponding average annual effective dose calculated to be 0.093 ± 0.028 mSv. The average activity concentrations of (238)U, (232)Th, and (40)K in the soil, rock, and ore samples were 65.1 ± 2.2, 71.8 ± 2.2 and 1168.3 Bqkg(-1) respectively resulting in an average annual effective dose of 0.91 ± 0.32 mSv. The average Radium equivalent activity value was 257.8 ± 62.4 Bqkg(-1) in the range of 136.6-340.2 Bqkg(-1). The average values of external and internal indices were 0.7 ± 0.2 and 0.9 ± 0.2 respectively. The average gross alpha and gross beta activity concentrations in the water samples were determined to be 0.0032 ± 0.0024 and 0.0338 ± 0.0083 Bql(-1) respectively. The total annual effective dose from the pathways considered for this study (gamma ray from the soil, rock and ore samples as well as doses determined from the gross alpha/beta activity concentration in water samples) was calculated to be 0.918 mSv. The results obtained in this study shows that the radiation levels are within the natural background radiation levels found in literature and compare well with similar studies for other countries and the total annual effective dose is below the ICRP recommended level of 1 mSv for public exposure control.

Reducing health risks from wastewater use in urban and peri-urban sub-Saharan Africa: applying the 2006 WHO guidelines.

Where rapid urbanization is outpacing urban capacities to provide sound sanitation and wastewater treatment, most water sources in city vicinity are heavily polluted. This is of great concern as many of the leafy vegetables eaten raw in the cities are produced in these areas. Following the new WHO guidelines, different non-treatment options at farm, market, and kitchen level were field tested for health risk reduction with special consideration to efficiency and adoption potential. As most households are used to vegetable washing (although ineffectively), an important entry point for risk reduction is the increased emphasis of the new guidelines on food preparation measures. A combination of safer irrigation practices (water fetching, on-farm treatment, and application), the allocation of farmland with better water sources, and improved vegetable washing in kitchens appear to be able to reduce the potential risk of infections significantly, although it might not be possible to reach the ideal threshold without some kind of wastewater treatment. The on-farm trials carried out in Ghana also explored the limitation of other risk reduction measures, such as drip irrigation, crop restrictions and cessation of irrigation under local circumstances considering possible incentives for behaviour change.

Effectiveness of common and improved sanitary washing methods in selected cities of West Africa for the reduction of coliform bacteria and helminth eggs on vegetables.

OBJECTIVE: To analyse and improve the effectiveness of common indigenous washing methods for the reduction of faecal coliform (FC) populations on the surface of wastewater-irrigated vegetables and to determine simple factors affecting their efficacy. METHODS: Questionnaire interviews were used to gather information on common methods used for washing vegetables in seven West African countries. The efficacy of the most common decontamination methods was measured in terms of log reductions in FC populations on homogenised contaminated lettuce, cabbage and spring onion samples. RESULTS: The large majority of urban households and restaurants in the subregion are aware of vegetable-related health risks and wash vegetables before consumption. Methods used vary widely within and between Ghana and neighbouring francophone West African countries. However, several of the most common methods do not reduce the contamination to any desirable level. Significantly, different log reductions are achieved depending on the washing method, contact time and water temperature. Tests to improve the apparent ineffective methods were especially promising in view of the relatively expensive vinegar. However, up to 3 log units reduction is also possible at a much lower price with 'Eau de Javel' (household bleach), which is commonly used in francophone West Africa. CONCLUSION: Washing vegetables before consumption is an important component of a multiple barrier approach for health risk reduction. The high risk perception among consumers demands that more information be made available on the appropriate use of these washing methods. Any washing method will need complementary efforts to reduce contamination before the vegetables enter the kitchen, such as safer irrigation practices.

Irrigated urban vegetable production in Ghana: microbiological contamination in farms and markets and associated consumer risk groups.

Ghana is a typical low-income sub-Saharan African country facing significant sanitation challenges. In Ghana, fresh salads are not part of the normal diet, but have become a common supplement to urban fast food served in streets, canteens and restaurants. In Accra, about 200 000 people consume from such supplements every day. The figure also describes the size of the risk group from contamination, which comprises all income classes including the poor and children. The purpose of this study was to investigate widespread water pollution in urban and peri-urban areas, where 95% of the lettuce consumed in the city is produced. Over 12 months (April 2004-June 2005), lettuce samples from the same production sites in two cities were followed and analyzed along the "farm to fork" pathway for total and faecal coliform (FC) and helminth egg numbers. Questionnaire surveys were conducted among producers, sellers and consumers to quantify lettuce flows to the final risk group. The study identified the farm as the main point of lettuce contamination. Besides the irrigation water, contamination was also attributed to manure application and already contaminated soil. Despite poor sanitary conditions in markets, post-harvest handling and marketing did not further increase the farm-gate contamination levels. To reduce the health risk associated with the consumption of contaminated lettuce; safer farming and irrigation practices are required while the remaining risk could best be addressed where lettuce is prepared for consumption.

Pesticide and pathogen contamination of vegetables in Ghana's urban markets.

The objective of the study was to determine and compare the current level of exposure of the Ghanaian urban population to hazardous pesticide and fecal coliform contamination through the consumption of fresh vegetables produced in intensive urban and periurban smallholder agriculture with informal wastewater irrigation. A total of 180 vegetable samples (lettuce, cabbage, and spring onion) were randomly collected under normal purchase conditions from 9 major markets and 12 specialized selling points in 3 major Ghanaian cities: Accra, Kumasi and Tamale. The samples were analyzed for pesticide residue on lettuce leaves, total and fecal coliforms, and helminth egg counts on all three vegetables. Chlopyrifos (Dursban) was detected on 78% of the lettuce, lindane (Gamalin 20) on 31%, endosulfan (Thiodan) on 36%, lambda-cyhalothrin (Karate) on 11%, and dichloro-diphenyl-trichloroethane on 33%. Most of the residues recorded exceeded the maximum residue limit for consumption. Vegetables from all 3 cities were fecally contaminated and carried fecal coliform populations with geometric mean values ranging from 4.0 x 10(3) to 9.3 x 10(8) g(-1) wet weight and exceeded recommended standards. Lettuce, cabbage, and spring onion also carried an average of 1.1, 0.4, and 2.7 helminth eggs g(-1), respectively. The eggs were identified as those of Ascaris lumbricoides, Ancylostoma duodenale, Schistosoma heamatobium, and Trichuris trichiura. Because many vegetables are consumed fresh or only slightly cooked, the study shows that intensive vegetable production, common in Ghana and its neighboring countries, threatens public health from the microbiologic and pesticide dimensions. Standard recommendations to address this situation (better legislations, law enforcement, or integrated pest management) often do not match the capabilities of farmers and authorities. The most appropriate entry point for risk decrease that also addresses postharvest contamination is washing vegetables before food preparation at the household or "chop" bar (street restaurant).