La roca magica: uses of natural zeolites in agriculture and industry.
(9/3155)
For nearly 200 years since their discovery in 1756, geologists considered the zeolite minerals to occur as fairly large crystals in the vugs and cavities of basalts and other traprock formations. Here, they were prized by mineral collectors, but their small abundance and polymineralic nature defied commercial exploitation. As the synthetic zeolite (molecular sieve) business began to take hold in the late 1950s, huge beds of zeolite-rich sediments, formed by the alteration of volcanic ash (glass) in lake and marine waters, were discovered in the western United States and elsewhere in the world. These beds were found to contain as much as 95% of a single zeolite; they were generally flat-lying and easily mined by surface methods. The properties of these low-cost natural materials mimicked those of many of their synthetic counterparts, and considerable effort has made since that time to develop applications for them based on their unique adsorption, cation-exchange, dehydration-rehydration, and catalytic properties. Natural zeolites (i.e., those found in volcanogenic sedimentary rocks) have been and are being used as building stone, as lightweight aggregate and pozzolans in cements and concretes, as filler in paper, in the take-up of Cs and Sr from nuclear waste and fallout, as soil amendments in agronomy and horticulture, in the removal of ammonia from municipal, industrial, and agricultural waste and drinking waters, as energy exchangers in solar refrigerators, as dietary supplements in animal diets, as consumer deodorizers, in pet litters, in taking up ammonia from animal manures, and as ammonia filters in kidney-dialysis units. From their use in construction during Roman times, to their role as hydroponic (zeoponic) substrate for growing plants on space missions, to their recent success in the healing of cuts and wounds, natural zeolites are now considered to be full-fledged mineral commodities, the use of which promise to expand even more in the future. (+info)
AIDS: what does economics have to offer?
(10/3155)
AIDS is rapidly becoming a major health problem in developing countries. Limited empirical information is available about the impact of AIDS on the household, the community, the health sector and the broader economy. Special problems exist in estimating the direct economic costs of AIDS in developing countries, including large out-of-pocket expenditures on health care and shortages of drugs and supplies; the difficulties of valuing resources used in caring for people with AIDS; and the lack of treatment alternatives. The calculation of indirect costs is complicated by difficulties in calculating the value of non-market production and international comparisons of the value of healthy life years lost may be erroneous, due to the higher level of average wages in developed countries. Existing evidence on the impact of AIDS at the household, community, sectoral and macroeconomic level is reviewed. Special attention is given to the impact of AIDS on the health sector and the resource allocation decisions which are made at this level. A policy-relevant research strategy would include addressing the particular information needs of the health sector, as well as studies which can help to inform government policy to mitigate the impact of AIDS at the household, community, sectoral and macroeconomic levels. (+info)
Gender, work and illness: the influence of a research unit on an agricultural community in The Gambia.
(11/3155)
Changes in employment opportunities and medical services are exploited by men and women in different ways. This paper examines gender-based variation in the selective use of employment and health opportunities in a Gambian village which has been the subject of medical and nutritional research by the Medical Research Council (MRC) for 43 years. The seasonal workloads of 105 men and women in Keneba were compared during one calendar year. Women carried a heavier burden of agricultural labour, while men had a higher rate of waged employment. The impact of the MRC field station on the local economy was assessed and evidence of associated male dependence on MRC employment found. Illness reporting patterns and the treatment choices of men and women were examined. Women made greater use of the MRC medical service, while men resorted more frequently to local remedies and healers. Female dependence on the MRC medical services is suggested by the data, and may be linked to the greater attention paid to them by researchers and medical practitioners. (+info)
Bancroftian filariasis in an irrigation project community in southern Ghana.
(12/3155)
An epidemiological study to document the endemicity and transmission characteristics of bancroftian filariasis was conducted in an irrigation project community in southern Ghana. In a 50% random sample of the population, the prevalence of microfilaraemia was 26.4% and the geometric mean microfilarial intensity among positives was 819 microfilariae/ml of blood. Hydrocoele was found in 13.8% of the males aged > or =18 years, and 1.4% of the residents examined, all females, had tymphoedema/elephantiasis. Detailed monitoring of the microfilarial intensity in 8 individuals over a 24-h period confirmed its nocturnal periodicity with a peak at approximately 0100 hours. The most important vector was Anopheles gambiae s.l., followed by An. funestus. The abundance of these mosquitoes and their relative importance as vectors varied considerably between the wet and the dry season. Opening of the irrigation canals late in the dry season resulted in a remarkable increase in the population of An. gambiae (8.3% of which carried infective filarial larvae) to levels comparable to those seen during the wet season, suggesting that the irrigation project is responsible for increased transmission of lymphatic filariasis in the community. (+info)
Comparative personal exposures to organic dusts and endotoxin.
(13/3155)
The aims of the study were to provide valid comparative data for personal exposures to dust and endotoxins for different occupations and to calculate comparative data for the contamination of organic dusts with endotoxin. Nine different occupational settings were studied, drawn from the textile, agricultural and animal handling industries. Samples were collected by personal sampling techniques, using the Institute of Occupational Medicine (IOM) sampling head, glass fibre filters and rechargeable sampling pumps. The dust exposures were calculated by gravimetric analysis and using the calculated volume of air sampled were expressed as mg/m3. Endotoxin exposures were measured using a simple water extraction from the collected dusts, followed by a quantitative turbidimetric assay. Results were expressed as ng/m3, using the calculated volume of air sampled. In addition, the levels of the contamination of dusts with endotoxin for individual industries were expressed as ng/mg of collected dust. Two hundred and fifty-nine samples, collected from 9 different industries and across 36 different sites were analysed. This represented a sampling rate of 25% for the total work force. The average sampling time was 4.62 h. For all the dusts collected, a significant correlation between the collected dust and endotoxin was seen (r = 0.7 and p < 0.001). The highest dust exposures occurred during cleaning activities (grain handling: 72.5 mg/m3). The individuals exposed to the highest median level of dust and endotoxin were the animal handlers (poultry handlers, dust: 11.53 mg/m3, endotoxin: 71,995 ng/m3). Weaving and mushroom cultivation had the lowest exposures for dust and endotoxins. The mostly highly contaminated dusts (median values expressed as ng of endotoxin per mg of collected dust) were found in the animal handling (poultry: 1,030 ng/mg, swine: 152 ng/mg) and cotton spinning (522 ng/mg) industries. Processing of cotton and wool fibres was found to reduce the levels of contamination of dusts with endotoxin. In the study, valid comparative data for personal exposures to organic dusts and endotoxins have been presented. The highest exposures were found amongst animal handlers and during cleaning activities. The results highlight that dust exposures are greater in a number of industries than the set exposure standards. In addition, endotoxin exposures are found to be greater than levels at which harmful effects have been demonstrated. (+info)
Back pain among persons working on small or family farms--eight Colorado counties, 1993-1996.
(14/3155)
In the United States, work-related back pain often results in lost wages, reduced productivity, and increased medical costs. However, national surveillance data about these injuries, such as occupationally acquired back pain among workers on small or family farms, are limited. To characterize back pain in a farming population, researchers at Colorado State University interviewed adult farmers residing in eight northeastern Colorado counties (Larimer, Logan, Morgan, Phillips, Sedgewick, Washington, Weld, and Yuma) during 1993-1996, using the Colorado Farm Family Health and Hazard Survey (CFFHHS). This report summarizes the findings of CFFHHS, which indicate that back pain is common among farmers and most frequently attributed to repeated activities (RAs) (e.g. lifting, pushing, pulling, bending, twisting, and reaching). (+info)
The growth of demand will limit output growth for food over the next quarter century.
(15/3155)
The rate of growth of world food demand will be much slower for 1990-2010 than it was for the prior three decades. The major factor determining the increase in food demand is population growth. Income growth has a much smaller effect. From 1960 to 1990, population growth accounted for approximately three fourths of the growth in demand or use of grain. For 1990-2010, it is anticipated that population growth will account for nearly all of the increase in world demand for grain. The rate of population growth from 1990 to 2020 is projected to be at an annual rate of 1.3% compared with 1.9% for 1960 to 1990-a decline of more than 30%. World per capita use of grain will increase very little-perhaps by 4%. The increase in grain use is projected to be 40% less than in 1960-1990. It is anticipated that real grain prices will decline during the period, although not nearly as much as the 40% decline in the previous three decades. Concern has been expressed concerning the deterioration of the quality and productivity of the world's farmland. A study for China and Indonesia indicates that there has been no significant change in the productive capacity of the land over the past 50 years. Contrary to numerous claims, the depth of the topsoil has not changed, indicating that erosion has had little or no impact. (+info)
Global and local implications of biotechnology and climate change for future food supplies.
(16/3155)
The development of improved technology for agricultural production and its diffusion to farmers is a process requiring investment and time. A large number of studies of this process have been undertaken. The findings of these studies have been incorporated into a quantitative policy model projecting supplies of commodities (in terms of area and crop yields), equilibrium prices, and international trade volumes to the year 2020. These projections show that a "global food crisis," as would be manifested in high commodity prices, is unlikely to occur. The same projections show, however, that in many countries, "local food crisis," as manifested in low agricultural incomes and associated low food consumption in the presence of low food prices, will occur. Simulations show that delays in the diffusion of modern biotechnology research capabilities to developing countries will exacerbate local food crises. Similarly, global climate change will also exacerbate these crises, accentuating the importance of bringing strengthened research capabilities to developing countries. (+info)