Economic and demographic factors affecting mangrove loss in the coastal provinces of Thailand, 1979-1996

The following paper analyzes the economic and demographic factors determining the conversion of mangroves in the coastal provinces of Thailand to commercial shrimp farming. Mangrove conversion therefore is determined by the returns to shrimp farmers, (i.e. the price of shrimp), the input costs to farming shrimp (e.g. feed price and wages) and the "accessibility" of mangrove areas. Additional exogenous influences, such as income per capita, population growth, and in-migration (i.e. the number of shrimp farms) also are important. Both a mangrove conversion and a shrimp farm expansion relationship are estimated empirically through a panel analysis across 21 coastal provinces of Thailand between 1979-1996. Results show that the price of shrimp, minimum wage, distance from market, feed price, population growth, income per capita, and shrimp-farm density all have important influences on mangrove loss due to shrimp farming in Thailand.     

Mutual pheromonal inhibition among queens in polygyne colonies of the fire ant Solenopsis invicta

Summary Decrease in individual reproductive output with increasing numbers of reproductives is a general feature of social insect colonies. The previously described negative relationship between the fecundity of individual queens and number of resident queens in polygyne (multiple-queen) colonies of the fire ant Solenopsis invicta appears to result from mutual pheromonal inhibition. In an experimental test for the presence of fecundity reducing pheromones, corpses of functional (egg-laying) queens were found to effectively inhibit the fecundity of functional queens, suggesting that queen-produced pheromones suppress egg production in such queens. Evidence concerning a possible mechanism mediating this inhibition was also obtained. Treatment of queens with methoprene, a juvenile hormone (JH) analog, increased ovary development, suggesting that fecundity in functional queens may be mediated by the level of endogenous JH. These findings are consistent with the occurrence of mutual pheromonal inhibition among queens achieved by suppression of endogenous JH titers.     

Road rage experience and behavior: vehicle, exposure, and driver factors

Road rage has generated increasing public concern. Research has shown that victimization and perpetration of road rage is more common among males and younger drivers. We aimed to extend the understanding of determinants of road rage to driving exposure and vehicle factors, based on a 20022003 population survey of 1,631 regular drivers in Ontario, Canada. Regression analyses revealed that number of times drivers reported experiencing road rage in the previous 12 months was significantly greater for males, younger respondents, and those residing in Toronto. Also, victimization was significantly greater for drivers who did all their driving on busy roads and increased with number of kilometers driven on a typical week; however, type of vehicle driven was not significant. Number of times road rage perpetration was reported in the past 12 months was significantly greater for males, younger respondents, and those residing in Toronto, and lower for those in the Eastern and Northern region. Road rage perpetration increased significantly with number of weekly kilometers driven and was significantly greater for drivers who are always on busy roads and lower for those who never drive on busy roads, and higher for high-performance vehicle drivers. Even after controlling for driving exposure, road rage victimization and perpetration were highest for drivers in Toronto, where the pace of life may be more demanding. As expected, high-performance vehicle drivers reported more road rage perpetration. These individuals may experience more frustration when they are prevented from using the full performance capacities of their vehicles by crowded urban roadways.     

PCB congener distribution in estuarine water,sediment and fish samples: implications for monitoring programs

Traditional analyses for PCBs in environmental matrices havefocused on commercial Aroclor mixtures with detection limits inthe 100 to 1000 part per trillion range. This approach hasrecently been supplanted by analyses for specific PCB compoundscalled congeners with detection limits less than 0.5 ppt. At thenational level, total PCB determinations based upon selected PCBcongeners typically characterize analyses of surface water,sediment and tissue. These federal efforts rely on a suite of 18to 20 congeners out of a total of 209 congeners to characterizetotal PCB. The present study compares total PCB estimates basedupon this subset of congeners with estimates based upon anexpanded list of 81 congeners from water, sediment and fishtissue collected from the Delaware Estuary.Analytical data from monitoring programs conducted in theDelaware Estuary by the Delaware River Basin Commission, NOAANational Ocean Service, U.S. Army Corps of Engineers and the U.S.Environmental Protection Agency from 1996 to 1998 were evaluated. Total PCB estimates derived from the different sets of congeners,including the adjustment factor of 2.0 used by NOAA, werecompared. This evaluation indicated that differences existbetween total PCB determinations based upon these approaches, andthat these differences vary depending on the matrix analyzed. The bias associated with using a smaller set of PCB congeners,and the implications for risk assessment are discussed.     

Mortality,violence and lack of access to healthcare in the Democratic Republic of Congo

The people of the Democratic Republic of Congo for decades have been living in a situation of chronic crisis. Violence, population displacement and the destruction of infrastructure and health services have devastated the health of the population. In 2001, Médicins Sans Frontières conducted a survey in five areas of western and central DRC to assess mortality, access to health-care, vaccination coverage and exposure to violence. High mortality rates were found in front-line zones, mainly due to malnutrition and infectious diseases. In Basankusu approximately 10 per cent of the total population and 25 per cent of the under-five population had perished in the year before the survey. Humanitarian needs remain acute across the country, particularly near the front line. Infectious-disease control and treatment are a priority, as is increasing access to health-care. Humanitarian assistance must be increased considerably, especially in rural areas and zones that have been affected directly by conflict.     

Hormesis and stage specific toxicity induced by cadmium in an insect model,the queen blowfly,Phormia regina Meig

Hormesis is an adaptive response, commonly characterized by a biphasic dose-response that can be either directly induced, or the result of compensatory biological processes following an initial disruption in homeostasis [Calabrese and Baldwin, Hum. Exp.Toxicol., 21 (2002), 91]. Low and environmentally relevant levels of dietary cadmium significantly enhanced the pupation rate of blowfly larvae, while higher doses inhibited pupation success. However, dietary cadmium at all exposure levels adversely affected the emergence of the adult fly from the pupal case. Such findings represent the first report of a heavy metal displaying a hormetic-like biphasic response for pupation success, while at the same time displaying stage-specific toxicity at a later developmental period.These conclusions are based on substantial experimentation of over 1750 blowflies, in seven replicate experiments, involving 10 concentrations per experiment. These findings indicate the need to assess the impact of environmental stressors over a broad range of potential exposures as well as throughout the entire life cycle.