Similar Mortality Patterns Research Articles

Alcohol-related and hepatocellular cancer deaths by country of birth in England and Wales: analysis of mortality and census data

The incidence of and mortality from alcohol-related conditions, liver disease and hepatocellular cancer (HCC) are increasing in the UK. We compared mortality rates by country of birth to explore potential inequalities and inform clinical and preventive care. Analysis of mortality for people aged 20 years and over using the 2001 Census data and death data from 1999 and 2001-2003. England and Wales. Standardized mortality ratios (SMRs) for alcohol-related deaths and HCC. Mortality from alcohol-related deaths (23 502 deaths) was particularly high for people born in Ireland (SMR for men [M]: 236, 95% confidence interval [CI]: 219-254; SMR for women [F]: 212, 95% CI: 191-235) and Scotland (SMR-M: 187, CI: 173-213; SMR-F 182, CI: 163-205) and men born in India (SMR-M: 161, CI: 144-181). Low alcohol-related mortality was found in women born in other countries and men born in Bangladesh, Middle East, West Africa, Pakistan, China and Hong Kong, and the West Indies. Similar mortality patterns were observed by country of birth for alcoholic liver disease and other liver diseases. Mortality from HCC (8266 deaths) was particularly high for people born in Bangladesh (SMR-M: 523, CI: 380-701; SMR-F: 319, CI: 146-605), China and Hong Kong (SMR-M: 492, CI: 168-667; SMR-F: 323, CI: 184-524), West Africa (SMR-M: 440, CI, 308-609; SMR-F: 319, CI: 165-557) and Pakistan (SMR-M: 216, CI: 113-287; SMR-F: 215, CI: 133-319). These findings show persistent differences in mortality by country of birth for both alcohol-related and HCC deaths and have important clinical and public health implications. New policy, research and practical action are required to address these differences.

Mapping infectious diseases in Africa

<h3>Aim</h3> The aim of this epidemiological study was to follow the time trends of mortality from gastric cancer and compare them with those of gastric and duodenal ulcer. <h3>Methods</h3> Mortality data from Denmark, England &amp; Wales, Italy, Japan, Switzerland and the United States of the past 57–130 years were analysed. The age-specific death rates were plotted against the period of death as period-age contours and against the period of birth as cohort-age contours. <h3>Results</h3> The long-term time trends of gastric cancer mortality were found to rise among generations born during the 18th century until the first half of the 19th century and then decline in all subsequent generations. The rise and fall of gastric cancer preceded similar birth-cohort patterns of gastric and duodenal ulcer by about 10–30 years. With the exception of gastric cancer in the USA, similar birth-cohort phenomena were seen in all countries. In general, similar temporal patterns were also seen in men and women analysed separately. <h3>Conclusions</h3> The time trends of mortality from gastric cancer are shaped by an underlying birth-cohort pattern that resembles similar patterns of peptic ulcer mortality. The occurrence of birth-cohort phenomena in gastric cancer and peptic ulcer suggests that additional secular trends besides changes in the infection with <i>Helicobacter pylori</i> must have contributed to the peculiar long-term behaviour of these diagnoses.

Taphonomic evidence of a Paleogene mammalian predator–prey interaction

A taphonomic study has been undertaken on an assemblage of bones and teeth of Isoptychus sp. and Thalerimys fordi (extinct rodent family Theridomyidae) from a single bed in a coastal plain setting, in the Late Eocene (Priabonian) Osborne Member, Headon Hill Formation (Hampshire Basin, UK). The vertebrate fossils show good preservation and do not bear the marks of obvious long distance transport. The two theridomyid species show similar patterns of mortality, element representation and surface modifications, which indicate similar mechanisms of accumulation. There is high mortality of juvenile and old individuals indicating accumulation of the assemblage by the action of attritional not catastrophic agents. The postcranial elements show fragmentary states and very low relative abundances. The vast majority of elongate bones (limb bones, phalanges and metapodials) are broken and exhibit a spiral irregular type of fracture with rounded fracture edges indicating that the bones were broken when they were fresh and have subsequently undergone additional modification. The enamel of most of the cheek teeth and incisors shows localized etching to various degrees and most of the bones show etching. By elimination of other modifying agents the observed etching is attributed to digestive corrosion. Collectively, these data indicate that the majority of the theridomyid individuals were eaten and digested by an animal that could cause high fragmentation during ingestion and with stomach juices of relatively high acidity. Both these features characterize mammalian carnivores. The presence of puncture marks on bones of both theridomyid species and comparisons with sizes of bite marks caused by extant mammalian carnivores suggest predation by a small mammalian carnivore about the size of an arctic fox. The extinct amphicyonid carnivoran Cynodictis cf. lacustris occurs in the same bed and the sizes of some of its teeth match well with the sizes of the puncture marks on the theridomyid bones. A predator–prey interaction is, therefore, deduced for the amphicyonid and the two theridomyid species, thereby reconstructing a small part of the continental Paleogene food chain.

Drought triggered tree mortality in mixed conifer forests in Yosemite National Park, California, USA

Tree mortality is an important process causing forest structural and compositional change. In this study, we investigate the influence of drought and topography on recent patterns of tree mortality in old-growth mixed conifer forests in Yosemite National Park, located in the Sierra Nevada Mountains of northern California, USA. The surveyed stands have experienced a century of fire exclusion and are dominated by associations of Pinus ponderosa, Calocedrus decurrens and Abies concolor. The average age of trees in the stands was 88 years. We sought answers to the following questions: (1) Do periods of high tree mortality correspond with drought? (2) Do spatial and temporal patterns of high tree mortality vary by slope aspect? and (3) Do different tree species exhibit similar temporal and spatial patterns of tree mortality? We identified temporal patterns of tree mortality on three north- and south-facing slopes by determining the death date of trees using dendrochronology. Tree death date frequency was then compared by slope aspect and to Palmer Drought Severity Index (PDSI), and April snowpack depth as measures of growing season water availability. The frequency of tree death dates was negatively correlated with annual and seasonal PDSI and April snowpack depth, and more trees died in years with below normal PDSI and snowpack. Correlations between tree mortality and drought were evident only for multi-year periods (2–5 years). Temporal patterns of tree death were similar on north- and south-facing slopes and among species, but the density of dead trees was higher on north than south slopes. Dense stand conditions caused by fire suppression, and the coincident outbreak of bark beetles during drought, may have limited any buffering effect of topography on tree mortality. Drought induced tree mortality in mixed conifer forests in Yosemite National Park highlights the importance of both historical legacies such as fire suppression and exogenous controls such as climate as drivers of vegetation change.

A study of inadvertent domestication selection during start‐feeding of brown trout families

A study was undertaken to compare first‐feeding mortality among 10 brown trout families fed high (100%) and low (25%) rations in replicate mixed family tanks. Microsatellite DNA profiling was used to assign individual brown trout to family of origin. At the end of the 35 day experimental period, highly significant differences in overall mortality were observed between the two treatments, and within the treatments there were highly significant differences in family mortality. Both replicates displayed similar patterns of family mortality. Notably, the distribution of mortality among families differed significantly between the two ration treatments, although this was more distinct for some families than others. No correlation between mean family egg diameter and family mortality were observed within either feeding treatment, although a significant positive correlation between mean family egg diameter and timing of family mortality was observed. It is suggested that these data indicate the existence of a genotype x environment interaction relating to feeding level during the critical start‐feeding period.

Attrition and bias in the MRC cognitive function and ageing study: an epidemiological investigation.

BackgroundAny hypothesis in longitudinal studies may be affected by attrition and poor response rates. The MRC Cognitive Function and Ageing study (MRC CFAS) is a population based longitudinal study in five centres with identical methodology in England and Wales each recruiting approximately 2,500 individuals. This paper aims to identify potential biases in the two-year follow-up interviews.MethodsInitial non-response: Those not in the baseline interviews were compared in terms of mortality to those who were in the baseline interviews at the time of the second wave interviews (1993–1996). Longitudinal attrition: Logistic regression analysis was used to examine baseline differences between individuals who took part in the two-year longitudinal wave compared with those who did not.ResultsInitial non-response: Individuals who moved away after sampling but before baseline interview were 1.8 times more likely to die by two years (95% Confidence interval(CI) 1.3–2.4) compared to respondents, after adjusting for age. The refusers had a slightly higher, but similar mortality pattern to responders (Odds ratio 1.2, 95%CI 1.1–1.4).Longitudinal attrition: Predictors for drop out due to death were being older, male, having impaired activities of daily living, poor self-perceived health, poor cognitive ability and smoking. Similarly individuals who refused were more likely to have poor cognitive ability, but had less years of full-time education and were more often living in their own home though less likely to be living alone. There was a higher refusal rate in the rural centres. Individuals who moved away or were uncontactable were more likely to be single, smokers, demented or depressed and were less likely to have moved if in warden-controlled accommodation at baseline.ConclusionsLongitudinal estimation of factors mentioned above could be biased, particularly cognitive ability and estimates of movements from own home to residential homes. However, these differences could also affect other investigations, particularly the estimates of incidence and longitudinal effects of health and psychiatric diseases, where the factors shown here to be associated with attrition are risk factors for the diseases.All longitudinal studies should investigate attrition and this may help with aspects of design and with the analysis of specific hypotheses.

Mortality patterns among residents in Louisiana’s industrial corridor, USA, 1970–99

Background: Because of the high concentration of oil refining and petrochemical facilities, the industrial area of the lower Mississippi River of South Louisiana has been termed the Industrial Corridor and...

A cohort mortality study among titanium dioxide manufacturing workers in the United States.

Although titanium dioxide (TiO2) is generally regarded as a nontoxic mild pulmonary irritant, some laboratory studies have reported lung adenomas in rats exposed to high levels of TiO2. Limited data on health effects among humans exist. A retrospective cohort mortality study was conducted among 4241 TiO2 workers who were employed for at least 6 months, on or after January 1, 1960, at four TiO2 plants in the United States. Exposure categories, defined by plant, job title, and calendar years in the job, were created to examine mortality patterns in those jobs where the potential for TiO2 exposure is greatest. Standardized mortality ratios (SMRs) and their 95% confidence intervals (CI) were calculated to compare the mortality pattern of the workers with the general background population. Relative risks were estimated and trend tests were conducted to examine risk of disease among different exposure level groups in internal analyses. Workers experienced a significantly low overall mortality (SMR = 0.8; 95% CI = 0.8-0.9). No significantly increased SMRs were found for any specific cause of death. Deaths from lung cancer were as expected, and SMRs for this cancer did not increase with increasing TiO2 levels. Workers in jobs with greatest TiO2 exposure had significantly fewer than expected total deaths (SMR = 0.7; 95% CI = 0.6-0.9). Internal analyses revealed no significant trends or exposure-risk associations for total cancers, lung cancer, or other causes of death. Results from our study indicate that the exposures at these United States plants are not associated with increases in the risk of death from cancer or other diseases. Moreover, workers with likely higher levels of TiO2 exposure had similar mortality patterns to those with less exposure, as internal analyses among workers revealed no increase in mortality by level of TiO2 exposure.

A multi-environment comparison of senescence between sister species of Daphnia

Senescence is a general decline of physiological state that accompanies advancing age. It affects nearly all organisms, but patterns of senescence vary markedly, even among closely related taxa. Understanding the evolution of this diversity requires information about environmental effects on the expression of variation among taxa. I examined genetically-based variation of senescence within and between two species complexes of Daphnia in four environments. The environments were defined by large differences in food and temperature, two factors known to influence senescence. The species studied were chosen to represent sister species that likely experience divergent (D. pulex and D. pulicaria) or similar (D. mendotate and D. dentifera) selection pressures on senescence. Overall, D. pulex expressed the greatest demographic senescence, D. mendotae and D. dentifera were intermediate, and D. pulicaria expressed the least. In environments representative of typical natural conditions, D. pulex had greater senescence than D. pulicaria, regardless of how late-life performance was assessed. This shows that genetic-environment interactions do not confound the interpretation of senescence differences between these species as the result of selective differences between their habitats. Comparison of D. mendotae and D. dentifera primarily revealed similar life histories, although differences in reproductive declines occurred in some environments. The joint observation of similar mortality patterns but dissimilar fecundity declines suggests that the trade-off between survival and reproduction changes with age. This calls into question the utility of only studying mortality for understanding evolutionary change of senescence in nature.

Development of a reproducible infectious pancreatic necrosis virus challenge model for Atlantic salmon, Salmo salar L.

AbstractAtlantic salmon smolts, previously unexposed to infectious pancreatic necrosis virus (IPNV), were placed into tanks of sea water at 10 °C. After 4 weeks, 40 fish were injected intraperitoneally (i.p.) with homogenized and filter‐sterilized kidney material obtained from salmon with clinical IPN in a marine farm in Shetland. The injected fish were cohabited with 40 untreated fish. Mortalities began in the injected fish on day 7 and reached a peak of 48% on day 14. In the cohabitation group, mortalities began on day 14 and reached a peak of 70% on day 27. The IPNV in the Shetland kidney homogenate was cultured in Chinook salmon embryo (CHSE) cells and passed twice. This cultured virus was injected i.p. into fish at various doses ranging from 10 to 107 TCID50 fish−1 4 weeks after seawater transfer. Challenge tanks contained 30 injected fish and 30 cohabitees. Mortality rates and levels were dose‐dependent. The highest dose used resulted in a similar mortality pattern as obtained with a similar dose of the Shetland kidney homogenate, indicating that virulence was retained after two passes in tissue culture. Even with the lowest dose, mortality reached 12% in the injected group and 23% in the cohabitees. The IPNV titres were high (106−109 i.u. g−1 kidney) in fish which died during the experiment and low (&lt;105 i.u. g−1 kidney) or undetectable in surviving fish. The cultured virus (pass 3) was used in a challenge model where the population density of fish in the tanks was high (50 injected and 50 cohabitees) or low (15 injected and 15 cohabitees). In the high stocking density tank, mortalities peaked at about 35% in the injected group and at 52% in the cohabitees. In the low stocking density tank, mortalities peaked at about 40% in the injected fish but no mortality occurred in the cohabitees. However, IPNV was detected (up to 104 i.u. g−1 kidney) in 82% of cohabitees sampled on day 30. These data suggest that lethal lateral transmission of the virus is dependent on the infectious pressure from the injected group. A further trial was conducted to investigate the effect of time post‐seawater transfer on the susceptibility of post‐smolts to IPN. Groups of fish were challenged every 2 weeks from week 0–10. Few mortalities occurred at week 0 and virus titres were high in these fish. Most survivors became carriers, some with titres &gt;106 i.u. IPNV g−1 kidney. From 2 to 10 weeks after seawater transfer, mortalities in both injected and cohabitees were substantial with viral titres &gt;107 i.u. g−1 kidney. Survivors had lower titres and in many virus was undetectable. Throughout the experiments, moribund fish were sampled for histology and all showed typical IPN histopathology.

Migration, growth and mortality of released reared and wild cod (Gadus morhua L.) in Malangen, northern Norway

In order to evaluate the potential of cod enhancement in a north Norwegian fjord, 4842 hatchery-reared cod juveniles (14-23 cm in length) were tagged and released into Stalvikbotn in 1988, a 10 km2 area sill fjord in Northern Norway. Wild cod were tagged to serve as a reference group for the hatchery-reared group. At the time of release, the size of the reared juvenile cod was about the same as that of the 1-year-older wild cod. The released fish showed a similar migration, growth and mortality pattern as wild fish of similar size. Both wild and released cod were mainly recaptured in Stalvikbotn. Large cod, short-horn sculpin and harp seal predated on the released reared juveniles. The recaptured reared cod were longer than average at release, indicating size-dependent predation mortality. The natural mortality rate (M) was estimated to be about 0.5 year-1 for cod longer than 30 cm and about 1.1 year-1 for both small wild and reared cod (14-30 cm). The fishing mortality rates were low, about 0.2 year-1 fo...

Effect of insecticides used in corn, sorghum, and alfalfa on the predator Orius insidiosus (Hemiptera: Anthocoridae).

Orius insidoisus (Say) is an important predator in corn, sorghum, and alfalfa. Foliar insecticides commonly used on corn (permethrin, bifenthrin, and fipronil); sorghum (chlorpyrifos, carbofuran, dimethoate, and cyfluthrin); and both crops (A-cyhalothrin and ethyl parathion) were evaluated in 1998 and 1999 for their residual effects on O. insidiosus by caging adults on treated plants at several time intervals: at application (day 0) and 2, 3, and 6 d after application. In addition, imidacloprid, fipronil, and thiamethoxam used as seed treatments on corn and sorghum were tested for their effects on O. insidiosus by caging adults on plants in the presence and absence of greenbugs, Schizaphis graminum (Rondani). Finally, six of the same insecticides that also are used on alfalfa were evaluated in the field for their effects on O. insidiosus and other insects. On day 0, ethyl parathion. bifenthrin, and [lambda]-cyhalothrin on corn caused significantly higher mortality to O. insidiosus than permethrin and fipronil. Ethyl parathion and carbofuran on sorghum caused significantly higher mortality than chlorpyrifos, dimethoate, and A-cyhalothrin, which differed significantly from the control. Mortality with cyfluthrin did not differ significantly from that in the control. Insecticides had no significant effects on O. insidiosus 3 and 6 d after application in 1998 with the exception of permethrin on day 3. Similar patterns of mortality were observed in 1999 experiments. No significant differences in mortality of adults occurred with fipronil and thiamethoxam in the presence and absence of greenbugs. Imidachloprid caused significantly higher mortality to O. insidiosus adults than thiamethoxam or fipronil in some instances when greenbugs were not supplied as food. In alfalfa, the insecticides caused significant mortality to most of the insects evaluated. Ethyl parathion, permethrin, chlorpyrifos, and cyfluthrin caused significantly higher mortality to O. insidiosus than carbofuran and A-cyhalothrin, which differed significantly from the control in 1998. In 1999, all treatments significantly reduced O. insidiosus numbers and did not differ significantly from each other.

Proposed explanations for excess injury among veterans of the Persian Gulf War and a call for greater attention from policymakers and researchers

Introduction—Death rates among US veterans of the Persian Gulf War were lower than rates among non-deployed veterans and the US population at large, with the exception of injury deaths; returning...

Cause‐specific mortality of people with intellectual disability in a population‐based, 35‐year follow‐up study

AbstractThe aim of the present study was to investigate cause‐specific mortality in people with intellectual disability (ID). It was based on a 35‐year follow‐up study of a nation‐wide population of 2369 subjects aged between 2 and 97 years. The 1095 deceased people had accumulated 64 539 person‐years. The research took the form of a prospective cohort study with mortality follow‐up. Observed and expected deaths were calculated as standardized mortality ratios using the Finnish general population as the reference. Cause‐specific mortality ratios were calculated by the level of ID, sex and age. The three most common causes of death were cardiovascular diseases, respiratory diseases and neoplasms. Disease mortality was high up to 40 years of age, but did not increase thereafter. The difference between sexes in cause‐specific mortality was smaller than in the general population. Cause‐specific mortality differed significantly from the general population, with reduced mortality from neoplasms and external causes, but ageing individuals with mild ID had similar mortality patterns to the general population. The disparities in the cause‐specific mortality between younger people with ID and the general population fade with advancing age, producing similar health risks. In preventative work, special attention should focus on common diseases and accidents in the community.

Cause-specific mortality of people with intellectual disability in a population-based, 35-year follow-up study.

The aim of the present study was to investigate cause-specific mortality in people with intellectual disability (ID). It was based on a 35-year follow-up study of a nation-wide population of 2369 subjects aged between 2 and 97 years. The 1095 deceased people had accumulated 64 539 person-years. The research took the form of a prospective cohort study with mortality follow-up. Observed and expected deaths were calculated as standardized mortality ratios using the Finnish general population as the reference. Cause-specific mortality ratios were calculated by the level of ID, sex and age. The three most common causes of death were cardiovascular diseases, respiratory diseases and neoplasms. Disease mortality was high up to 40 years of age, but did not increase thereafter. The difference between sexes in cause-specific mortality was smaller than in the general population. Cause-specific mortality differed significantly from the general population, with reduced mortality from neoplasms and external causes, but ageing individuals with mild ID had similar mortality patterns to the general population. The disparities in the cause-specific mortality between younger people with ID and the general population fade with advancing age, producing similar health risks. In preventative work, special attention should focus on common diseases and accidents in the community.

Mortality of Escherichia coli O157:H7 in Two Soils with Different Physical and Chemical Properties

AbstractWild and domesticated animals can harbor a pathogenic Escherichia coli strain designated as O157:H7. Potential health problems could occur if strain O157:H7 is a more robust survivor in defecated waste than commonly used indicator bacteria. A laboratory study was conducted to assess E. coli O157:H7 survival relative to a nonpathogenie E. coli strain in two soils with different physical and chemical characteristics. Bacteria in the inoculated soils were enumerated on a weekly basis for 8 wk using a most probable number (MPN) technique. First‐order decay models were used to describe bacteria mortality in the soils. Decay series were described slightly better by a two‐stage function than by a single‐stage function. Strain O157:H7 exhibited similar mortality patterns to the nonpathogenic E. coli in the same soil environment. Both E. coli strains had greater mortality rates in Pope silt loam (coarse‐loamy, mixed, active, mesic Fluventic Dystrudept) than Zanesville silt loam (fine‐silty, mixed, active, mesic Oxyaquic Fragiudalf). Differences in available soil water probably were the overriding factor in E. coli survival. Escherichia coli O157:H7 survival could be modeled in the same way as nonpathogenic E. coli and appears to have a slightly higher mortality rate.

Mortality Among North Carolina Construction Workers, 1988-1994

This study evaluated proportionate mortality patterns among all male construction workers in North Carolina who resided and died in North Carolina during the period 1988-1994. Proportionate Mortality Ratios (PMRs) and Proportionate Cancer Mortality Ratios (PCMRs) compared the number of deaths among male construction workers with the number of deaths expected based on the gender, race, and cause-specific mortality experience of the entire North Carolina population by five-year age groups for the same years of study. PMRs based on United States death rates also were calculated. Among all male construction workers, significantly elevated mortality was observed for several causes possibly related to work including malignant neoplasms of buccal cavity (PMR = 143), pharynx (PMR = 134), and lung (PMR = 113), pneumoconiosis (PMR = 111), transportation accidents (PMR = 106), and accidental falls (PMR = 132). Elevated mortality also was observed for causes more related to lifestyle and non-occupational factors including alcoholism (PMR = 145), cirrhosis of the liver (PMR = 129), accidental poisoning (PMR = 136), and homicide (PMR = 141). Patterns of elevated mortality for Whites and Black men were similar and PCMR mortality patterns for Blacks and Whites combined were similar to PMRs. Construction workers were at significantly increased risk for deaths resulting from falls from ladders or scaffolds, falls from or out of buildings or structures, and electrocutions. Construction trades found to have statistically elevated cancer risks include laborers and roofers (buccal cavity), painters (pharynx), laborers (peritoneum), and carpenters, painters, brick masons, and operating engineers (lung). These data are consistent with other reports demonstrating excess mortality from asbestos-related diseases (pneumoconiosis, lung cancer, and mesothelioma) among construction workers. Dry-wall workers and laborers were found to have a statistically elevated risk of death as a result of respiratory tuberculosis.

Fine root demography in alfalfa (Medicago sativa L.)

In perennial forages like alfalfa (Medicago sativa L.), repeated herbage removal may alter root production and mortality which, in turn, could affect deposition of fixed N in soil. Our objective was to determine the extent and patterns of fine-diameter root production and loss during the year of alfalfa stand establishment. The experiment was conducted on a loamy sand soil (Udorthentic Haploboroll) in Minnesota, USA, using horizontally installed minirhizotrons placed directly under the seeded rows at 10, 20, and 40 cm depths in four replicate blocks. We seeded four alfalfa germplasms that differed in N2 fixation capacity and root system architecture: Agate alfalfa, a winter hardy commercially-available cultivar; Ineffective Agate, which is a non-N2-fixing near isoline of Agate; a new germplasm that has few fibrous roots and strong tap-rooted traits; and a new germplasm that has many fibrous roots and a strongly branched root system architecture. Video images collected biweekly throughout the initial growing season were processed using C-MAP-ROOTS software. More than one-half of all fine roots in the upper 20 cm were produced during the first 7 weeks of growth. Root production was similar among germplasms, except that the highly fibrous, branch-rooted germplasm produced 29% more fine roots at 20 cm than other germplasms. In all germplasms, about 7% of the fine roots at each depth developed into secondarily thickened roots. By the end of the first growing season, greatest fine root mortality had occurred in the uppermost depth (48%), and least occurred at 40 cm (36%). Survival of contemporaneous root cohorts was not related to soil depth in a simple fashion, although all survivorship curves could be described using only five rates of exponential decline. There was a significant reduction in fine root mortality before the first herbage harvest, followed by a pronounced loss (average 22%) of fine roots at the 10- and 20-cm depths in the 2-week period following herbage removal. Median life spans of these early-season cohorts ranged from 58 to 131 days, based on fitted exponential equations. At all depths, fine roots produced in the 4 weeks before harvest (early- to mid-August) tended to have shorter median life spans than early-season cohorts. Similar patterns of fine root mortality did not occur at the second harvest. Germplasms differed in the pattern, but not the ultimate extent, of fine root mortality. Fine root turnover during the first year of alfalfa establishment in this experiment released an estimated 830 kg C ha−1 and 60 kg N ha−1, with no differences due to N2 fixation capacity or root system architecture.

Lobar pneumonia: an occupational disease in welders

Summary We have used data from three analyses of occupational mortality for England and Wales to investigate a suspected hazard of pneumonia in welders. Mortality from the disease was consistently raised in welders aged 15-64, with standardised mortality ratios of 184 (95% Cl 150-224) in 1959-63 and 157 (121-200) in 1970-72. Analysis of data for 1979-80 and 1982-90 showed that the increased risk is attributable mainly to an excess of pneumococcal and unspecified lobar pneumonia (proportional mortality ratio 255, 95% Cl 192-332). No excess occurred in men above retirement age (65). A possible explanation of these findings is that welding fume reversibly increases the susceptibility of the lung to pneumonic infection. The observation of a similar mortality pattern in moulders and coremakers points to the metallic component of the fume as a possible culprit, but ozone or oxides of nitrogen could also be implicated. There are grounds for lobar pneumonia to be considered an occupational disease in welders.

Disease risk as a cost of outbreeding in the termite Zootermopsis angusticollis.

The effect of the sibship of primary reproductives on mate mortality and the survivorship and growth of incipient colonies was studied in the dampwood termite Zootermopsis angusticollis. Males and females paired with nonsibling mates had higher mortality during the first 10-40 days after pairing, although male and female reproductives showed similar patterns of mortality after colony establishment. The source of mortality appeared to be fungal and/or bacterial pathogens. There were no overall differences in the number of eggs and larvae produced by sibling and nonsibling pairs, and no differences in colony size and biomass 4 years after colony establishment. We therefore could not identify any negative effect of inbreeding in the early phases of colony development. Our results suggest that the risk of exposure to pathogens and the ability of termites to locally adapt to disease could influence the genetic identity of primary reproductives and the extent of inbreeding in termite populations.