Lung cancer mortality among chromate production workers. (49/521)

AIMS: To assess mortality in 1997 among 493 former workers of a US chromate production plant employed for at least one year between 1940 and 1972. METHODS: Cohort members were followed for mortality to 31 December 1997. Standardised mortality ratios (SMRs) were calculated for selected cause specific categories of death including lung cancer. Lung cancer mortality was investigated further by calculation of SMRs stratified by year of hire, duration of employment, time since hire, and categories of cumulative exposure to Cr(VI). RESULTS: Including 51 deaths due to lung cancer, 303 deaths occurred. SMRs were significantly increased for all causes combined (SMR = 129), all cancers combined (SMR = 155), and lung cancer (SMR = 241). A trend test showed a strong relation between lung cancer mortality and cumulative hexavalent exposure. Lung cancer mortality was increased for the highest cumulative exposure categories (> or =1.05 to <2.70 mg/m(3)-years, SMR = 365; > or =2.70 to 23 mg/m(3)-years, SMR = 463), but not for the first three exposure groups. Significantly increased SMRs were also found for year of hire before 1960, 20 or more years of exposed employment, and latency of 20 or more years. CONCLUSIONS: The finding of an increased risk of lung cancer mortality associated with Cr(VI) exposure is consistent with previous reports. Stratified analysis of lung cancer mortality by cumulative exposure suggests a possible threshold effect, as risk is significantly increased only at exposure levels over 1.05 mg/m(3)-years. Though a threshold is consistent with published toxicological evidence, this finding must be interpreted cautiously because the data are also consistent with a linear dose response.  (+info)

A potential integrated water quality strategy for the Mississippi River Basin and the Gulf of Mexico. (50/521)

Nutrient pollution, now the leading cause of water quality impairment in the U.S., has had significant impact on the nation"s waterways. Excessive nutrient pollution has been linked to habitat loss, fish kills, blooms of toxic algae, and hypoxia (oxygen-depleted water). The hypoxic "dead zone" in the Gulf of Mexico is one of the most striking illustrations of what can happen when too many nutrients from inland watersheds reach coastal areas. Despite programs to improve municipal wastewater treatment facilities, more stringent industrial wastewater requirements, and agricultural programs designed to reduce sediment loads in waterways, water quality and nutrient pollution continues to be a problem, and in many cases has worsened. We undertook a policy analysis to assess how the agricultural community could better reduce its contribution to the dead zone and also to evaluate the synergistic impacts of these policies on other environmental concerns such as climate change. Using a sectorial model of U.S. agriculture, we compared policies including untargeted conservation subsidies, nutrient trading, Conservation Reserve Program extension, agricultural sales of carbon and greenhouse gas credits, and fertilizer reduction. This economic and environmental analysis is watershed-based, primarily focusing on nitrogen in the Mississippi River basin, which allowed us to assess the distribution of nitrogen reduction in streams, environmental co-benefits, and impact on agricultural cash flows within the Mississippi River basin from various options. The model incorporates a number of environmental factors, making it possible to get a more a complete picture of the costs and co-benefits of nutrient reduction. These elements also help to identify the policy options that minimize the costs to farmers and maximize benefits to society.  (+info)

Applying nitrogen site-specifically using soil electrical conductivity maps and precision agriculture technology. (51/521)

Soil texture varies significantly within many agricultural fields. The physical properties of soil, such as soil texture, have a direct effect on water holding capacity, cation exchange capacity, crop yield, production capability, and nitrogen (N) loss variations within a field. In short, mobile nutrients are used, lost, and stored differently as soil textures vary. A uniform application of N to varying soils results in a wide range of N availability to the crop. N applied in excess of crop usage results in a waste of the grower"s input expense, a potential negative effect on the environment, and in some crops a reduction of crop quality, yield, and harvestability. Inadequate N levels represent a lost opportunity for crop yield and profit. The global positioning system (GPS)-referenced mapping of bulk soil electrical conductivity (EC) has been shown to serve as an effective proxy for soil texture and other soil properties. Soils with a high clay content conduct more electricity than coarser textured soils, which results in higher EC values. This paper will describe the EC mapping process and provide case studies of site-specific N applications based on EC maps. Results of these case studies suggest that N can be managed site-specifically using a variety of management practices, including soil sampling, variable yield goals, and cropping history.  (+info)

Shorebird use of coastal wetland and barrier island habitat in the Gulf of Mexico. (52/521)

The Gulf Coast contains some of the most important shorebird habitats in North America. This area encompasses a diverse mixture of estuarine and barrier island habitats with varying amounts of freshwater swamps and marshes, bottomland hardwood forests, and coastal prairie that has been largely altered for rice and crawfish production, temporary ponds, and river floodplain habitat. For the purposes of this review, discussion is confined to general patterns of shorebird abundance, distribution, and macro- and microhabitat use in natural coastal, estuarine, and barrier island habitats on the Gulf of Mexico Coast. The following geographic regions are considered: Northwestern Gulf (Rio Grande to Louisiana-Mississippi border), Northeastern Gulf (Mississippi to Florida Keys), and Mexico (Rio Grande to Cabo Catoche [Yucatan Strait]). Wintering and migrating shorebirds are most abundant along the Gulf Coast in Texas and Tamaulipas, particularly the Laguna Madre ecosystem. Other important areas are the Southwest Coast region of Florida and the area between Laguna Terminos and Puerto Progresso in Mexico. In general, relative abundances of shorebirds increase from north to south, and decrease south of the Tropic of Cancer (23 degrees 27' N). Based on bimonthly maximum counts within 5 latitudinal bands, the region between 25-30 degrees N is used most heavily by wintering and spring migrating birds. Non-vegetated coastal wetland habitats associated with bays, inlets and lagoons, particularly tidal flats, and sandy beaches are the habitats that appear to be favored by wintering and migrating shorebirds. In general, these habitats tend to occur as habitat complexes that allow for movement between them in relation to tidal flooding of bay-shore habitats. This relationship is particularly important to Piping Plover and may be important to others. Although vegetated habitats are used by some species, they do not appear to attract large numbers of birds. This habitat is most widespread between the Texas-Louisiana border and the Florida Panhandle region, but it has not been studied extensively. Shorebird abundance and habitat use in this area need to be addressed.  (+info)

Short report: a new case report of human Mesocestoides infection in the United States. (53/521)

The twenty-seventh documented case of human Mesocestoides infection, which corresponds to the seventh documented case in the United States, is reported. The case had its origin in Alexandria, Louisiana in the summer of 1998. The patient was a 19-month-old boy. The strobila consisted of 35 proglottids that included mature as well as gravid segments containing a ventral genital pore and a parauterine organ. After a detailed microscopic examination, the tapeworm was identified as belonging to the genus Mesocestoides. Mesocestoides variabilis is the probable species responsible for the infection, since the six cases previously reported in the United States were identified as this species. After the treatment with a single dose of praziquantel (10 mg/kg), the tapeworm segments were no longer detectable in the child's feces. A food-borne origin of this infection derived from culinary customs of the Acadian and Creole communities in Louisiana is proposed.  (+info)

Surveillance for acute insecticide-related illness associated with mosquito-control efforts--nine states, 1999-2002. (54/521)

Ground and aerial applications of insecticides are used to control populations of adult mosquitoes, which spread such diseases as West Nile virus--related illness, eastern equine encephalitis, and dengue fever. This report summarizes investigations of illnesses associated with exposures to insecticides used during 1999-2002 to control mosquito populations in nine states (Arizona, California, Florida, Louisiana, Michigan, New York, Oregon, Texas, and Washington) (estimated 2000 population: 118 million). The findings indicate that application of certain insecticides posed a low risk for acute, temporary health effects among persons in areas that were sprayed and among workers handling and applying insecticides. To reduce the risk for negative health effects, public health authorities should 1) provide public notice of application times and locations and appropriate advice about preventing exposures, 2) ensure that insecticide handlers and applicators meet state-mandated training and experience requirements to prevent insecticide exposure to themselves and the public, and 3) implement integrated pest management control strategies that emphasize mosquito larval control, reduction of mosquito breeding sites, and judicious use of insecticides to control adult mosquito populations.  (+info)

A mortality and morbidity study of refinery and petrochemical employees in Louisiana. (55/521)

AIMS: To examine the mortality experience of 4221 employees from 1973 to 1999 and the illness absence patterns for 2203 employees from 1990 to 1999 of a chemical and refinery facility in Louisiana. METHODS: Mortality and illness absence data were extracted from the Shell Oil Company's health surveillance system (HSS). The standardised mortality ratio was used as a measure of mortality risk. Morbidity frequency and duration of absence were calculated by age, sex, and four health risk factors (cigarette smoking, high blood pressure, hypercholesterolaemia, and obesity). RESULTS: Male employees experienced a significant deficit in mortality for all causes of death, all cancers, lung cancer, heart disease, and respiratory disease compared with the corresponding US population. Brain cancer was non-significantly increased, with six observed and five expected deaths; mortality from leukaemia was consistently lower than expected. The majority of employees had no illness absences of six days or longer during the 10 year study period. The loss of productivity (in terms of days of absence) was greater for employees with health risk factors. Ever smoking male employees had a 79% increase of heart disease and more than 50% higher rates of respiratory disease and musculoskeletal disorders compared to non-smokers. Smokers were absent 2.9 and 1.6 more days than non-smokers and ex-smokers, respectively. CONCLUSIONS: Regardless of the comparison population, significantly fewer deaths were seen for all causes combined, all cancers, lung cancer, heart disease, or non-malignant respiratory disease. Illness absence rates and duration were higher among employees with health risk factors.  (+info)

The presence of two different infantile Tay-Sachs disease mutations in a Cajun population. (56/521)

A study was undertaken to characterize the mutation(s) responsible for Tay-Sachs disease (TSD) in a Cajun population in southwest Louisiana and to identify the origins of these mutations. Eleven of 12 infantile TSD alleles examined in six families had the beta-hexosaminidase A (Hex A) alpha-subunit exon 11 insertion mutation that is present in approximately 70% of Ashkenazi Jewish TSD heterozygotes. The mutation in the remaining allele was a single-base transition in the donor splice site of the alpha-subunit intron 9. To determine the origins of these two mutations in the Cajun population, the TSD carrier status was enzymatically determined for 90 members of four of the six families, and extensive pedigrees were constructed for all carriers. A single ancestral couple from France was found to be common to most of the carriers of the exon 11 insertion. Pedigree data suggest that this mutation has been in the Cajun population since its founding over 2 centuries ago and that it may be widely distributed within the population. In contrast, the intron 9 mutation apparently was introduced within the last century and probably is limited to a few Louisiana families.  (+info)