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At least 379 records · Page 21Linked to original sources
PubMed2003

Emission and long-range transport of gaseous mercury from a large-scale Canadian boreal forest fire.

Field observations made at Harvard Forest [Petersham, MA, U.S.A. (42 degrees 54' N, 72 degrees 18' W)] during early July 2002 show clear evidence of long-range transport of gaseous mercury (Hg) in a smoke plume from a series of boreal forest fires in northern Quebec. These measurements indicated significant and highly correlated increases in Hg and CO during the plume event. The Hg:CO emissions ratio determined from the data (8.61 x 10(-8) mol mol(-1)) was combined with previously published information on CO emissions and biomass burned to determine a mean area-based Hg emission flux density for boreal forest fires (1.5 g Hg ha(-1)), annual Hg emissions from Canadian forest fires (3.5 tonnes), and annual global Hg emissions from boreal forest fires (22.5 tonnes). Annual Hg emissions from boreal fires in Canada may equal 30% of annual Canadian anthropogenic emissions in an average fire year and could be as high as 100% during years of intense burning. The Hg:CO emissions ratio of this study was much lower than those reported for a temperate forest in Ontario and a pine/shrub vegetation in South Africa, suggesting that fire emission is dependent on biome/species and that any extrapolation from a single fire event to determine the global fire emission is speculative.

Air Movements↗
PubMed2001

Increased damage from fires in logged forests during droughts caused by El Niño.

In 1997-98, fires associated with an exceptional drought caused by the El Niño/Southern Oscillation (ENSO) devastated large areas of tropical rain forests worldwide. Evidence suggests that in tropical rainforest environments selective logging may lead to an increased susceptibility of forests to fire. We investigated whether this was true in the Indonesian fires, the largest fire disaster ever observed. We performed a multiscale analysis using coarse- and high-resolution optical and radar satellite imagery assisted by ground and aerial surveys to assess the extent of the fire-damaged area and the effect on vegetation in East Kalimantan on the island of Borneo. A total of 5.2 +/- 0.3 million hectares including 2.6 million hectares of forest was burned with varying degrees of damage. Forest fires primarily affected recently logged forests; primary forests or those logged long ago were less affected. These results support the hypothesis of positive feedback between logging and fire occurrence. The fires severely damaged the remaining forests and significantly increased the risk of recurrent fire disasters by leaving huge amounts of dead flammable wood.

Borneo↗
PubMed1990

Fire fighters' exposure to carbon monoxide during Australian bushfires.

Fatal entrapments of Australian bushfire fighters have led to suggestions that carbon monoxide (CO) poisoning could have contributed to these accidents by impairing the fire fighters' judgement. Carboxyhemoglobin saturation (COHb%) levels were assessed from alveolar CO levels in 24 fire fighters working with handtools and in 12 accompanying scientific observers, before and after fire fighting (duration 37-187 min) on 15 experimental bushfires. Carboxyhemoglobin levels increased on average by 0.7% per hour in the fire fighters and by 0.3% per hour in the observers. Nonsmoking fire fighters had lower COHb% after fires than the smokers had before fires. Estimates of environmental CO concentrations (including cigarette smoke) during the fires averaged 31 parts per million (ppm) for the smokers, 17 ppm for the nonsmoking crew members, and 11 ppm for the observers, none of whom smoked. The highest estimates of environmental CO arising solely from bushfire smoke were 40 to 50 ppm. Smokers were exposed to as much CO from their cigarettes as from bushfire smoke. Carboxyhemoglobin levels at the end of 8-hr fire fighting shifts, predicted from these levels of environmental CO, averaged about 5% (maximum 11%) in smokers and about 3% (maximum 7%) in nonsmokers. Acute levels of COHb% of this degree are not considered to have significant effects on health or performance. These results indicate that bushfire fighters are generally unlikely to experience hazardous levels of CO exposure.

Adult↗
PubMedDate not supplied

Fire fatalities among children: an analysis across Philadelphia's census tracts.

OBJECTIVE: This study investigates the possible causes of high levels of residential fire deaths to children younger than 15 years of age in Philadelphia from 1989 to 2000. METHODS: The authors analyzed 246 deaths from 146 residential fires by census tract in Philadelphia using both individual level data and aggregate level data drawn from the records of the Fire Marshall's Office. Death rates by age and sex were calculated using the 1990 Census. Data on fires from official records were combined with aggregate level data by census tract from the 1990 Census and analyzed using logistic regression. Newspaper articles on the fires analyzed were used to identify residences with possible fire code violations. The authors used data from the Philadelphia Bureau of Licenses and Inspections to provide evidence of code violations. RESULTS: The statistically significant variables that resulted from the logistic regression were census tracts in the highest quartile for low income households, census tracts in the highest quartile for single-parent households with children younger than age 18, census tracts in the highest quartile for houses built before 1939, and the number of children younger than 15 years of age in a census tract. CONCLUSION: Population characteristics by census tract are useful in identifying risk factors for residential fire deaths of children. Census tracts identified as at highest risk can provide fire prevention units with opportunities to take preventative measures such as the distribution of smoke detectors, and the education of residents about the dangers of careless smoking and planning for the rescue of children in the event of a fire.

Adolescent↗
PubMedDate not supplied

Substance abuse in victims of fire.

Ethanol or drug use may increase the risk of fire-related injury or death. This study was performed to quantify the role of substance abuse in fatal fires occurring in New Jersey over a 7-year period. Records of all the fatalities of fire reported to the State Medical Examiners Office between 1985 and 1991 were retrospectively examined. Blood assay results for ethanol were positive in 215 of the 727 (29.5%) fatalities of fire tested. For this group, the mean blood-ethanol level was 193.9 mg/dl. Blood or urine assay results for substances of abuse were positive in 78 of the 534 (14.6%) fatalities tested. The most commonly detected illicit substances were cocaine, benzodiazepines, barbiturates, and cannabinoids. The test results were positive for both ethanol and drug use in 36 victims. Forty percent of all the fatalities of fire were aged younger than 11 or older than 70. In contradistinction, 75% of drug-positive fatalities of fire and 58% of ethanol-positive fatalities of fire were between the ages of 21 and 50, suggesting that inebriation may impair the ability to escape from fire. Substance abusers in middle life are a previously unrecognized group at higher risk of injury or death in a fire.

Adolescent↗
PubMed1983

Heart rates in fire fighters using light and heavy breathing equipment: similar near-maximal exertion in response to multiple work load conditions.

Intense exertion is an occupational hazard inherent to fire fighting. This study was designed to look at the exertion levels that fire fighters attain during a fire fighting exercise when using (1) no self-contained breathing apparatus (SCBA), (2) light SCBA, and (3) heavy SCBA. Exertion levels were measured as a function of the heart rate increase relative to the maximum predicted heart rate determined by a standard treadmill exercise test. Five fire fighters wore electrocardiographic monitors during a routine fire fighting exercise. Heart rates increased rapidly to 70% to 80% of maximum within the first minute and then plateaued at 90% to 100% until the attack on the fire was completed. There was no significant difference between exertion levels when using no SCBA, light SCBA, and heavy SCBA (split-plot analysis of variance, p greater than .25). These results suggest that fire fighters attain an intense level of physical activity quickly and maintain that level as long as they are actively engaged in fighting fire. These results also suggest that regardless of the weight of the SCBA, if employed, fire fighters exert themselves from 85% to 100% of their maximum and adjust their work output to maintain that near-maximal level.

Adult↗
PubMed2005

The global distribution of ecosystems in a world without fire.

This paper is the first global study of the extent to which fire determines global vegetation patterns by preventing ecosystems from achieving the potential height, biomass and dominant functional types expected under the ambient climate (climate potential). To determine climate potential, we simulated vegetation without fire using a dynamic global-vegetation model. Model results were tested against fire exclusion studies from different parts of the world. Simulated dominant growth forms and tree cover were compared with satellite-derived land- and tree-cover maps. Simulations were generally consistent with results of fire exclusion studies in southern Africa and elsewhere. Comparison of global 'fire off' simulations with landcover and treecover maps show that vast areas of humid C(4) grasslands and savannas, especially in South America and Africa, have the climate potential to form forests. These are the most frequently burnt ecosystems in the world. Without fire, closed forests would double from 27% to 56% of vegetated grid cells, mostly at the expense of C(4) plants but also of C(3) shrubs and grasses in cooler climates. C(4) grasses began spreading 6-8 Ma, long before human influence on fire regimes. Our results suggest that fire was a major factor in their spread into forested regions, splitting biotas into fire tolerant and intolerant taxa.

Biological Evolution↗
PubMed1998

The potential benefit of a home fire safety intervention during emergency medical services calls.

OBJECTIVE: To determine how often house fires occur at 1- and 2-family dwellings visited previously by emergency medical services (EMS) personnel and whether these visits were missed opportunities for a point-of-contact home fire safety intervention. METHODS: A retrospective, consecutive, case series analysis of all Milwaukee Fire Department alarm responses during 1994 was performed. Measurements included date of service, type of response, property type, dollar loss estimate, number of injuries and fatalities, cause of alarm, and presence of an operational smoke detector. Descriptive, chi2, and relative risk statistics were used to describe the relationship between EMS responses and fire responses at 1- and 2-family dwellings. RESULTS: The Milwaukee Fire Department dispatched 94,378 requests for service to 43,556 addresses. 16,150 addresses generated multiple requests; 7.2% (1,162/16,150) were for an "alarm of fire" response [relative risk 1.83 (95% CI: 1.69-1.99) for addresses with multiple requests vs those with a single request for service]. Most [62% (721/1,162)] of the addresses were visited by EMS personnel prior to the alarm; 28% (205/721) were 1- and 2-family dwellings. A mean of 1.8 (376/205) EMS responses occurred prior to the "alarm of fire" response; 121 addresses received 1 response, 46 received 2, 18 received 3, and 20 received > or = 4 responses. Of 169 addresses with complete data, there was a total fire dollar loss of $1,963,020 (1994) along with 32 injuries and 0 fatalities. While 47% (80/169) of the 1- and 2-family dwellings had a smoke detector present, only 17% (29/169) of the dwellings had an operational smoke detector. CONCLUSIONS: A point-of-contact home fire safety intervention appears of potential benefit for frequent users of EMS care. Determination of the presence of an operational smoke detector in 1- and 2-family dwellings may be a useful injury prevention act during such EMS calls.

Accident Prevention↗
PubMed2004

Past, current and future fire frequency in the Canadian boreal forest: implications for sustainable forest management.

Over the past decades, there has been an increasing interest in the development of forest management approaches that are based on an understanding of historical natural disturbance dynamics. The rationale for such an approach is that management to favor landscape compositions and stand structures similar to those of natural ecosystems should also maintain biological diversity and essential ecological functions. In fire-dominated landscapes, this approach is possible only if current and future fire frequencies are sufficiently low, comparing to pre-industrial fire frequency, that we can substitute fire by forest management. We address this question by comparing current and future fire frequency to historical reconstruction of fire frequency from studies realized in the Canadian boreal forest. Current and simulated future fire frequencies using 2 and 3 x CO2 scenarios are lower than the historical fire frequency for many sites, suggesting that forest management could potentially be used to recreate the forest age structure of fire-controlled pre-industrial landscapes. There are however, important limitations to the current even-age management.

Canada↗
PubMed2006

Climate effects on fire regimes and tree recruitment in Black Hills ponderosa pine forests.

Climate influences forest structure through effects on both species demography (recruitment and mortality) and disturbance regimes. Here, I compare multi-century chronologies of regional fire years and tree recruitment from ponderosa pine forests in the Black Hills of southwestern South Dakota and northeastern Wyoming to reconstructions of precipitation and global circulation indices. Regional fire years were affected by droughts and variations in both Pacific and Atlantic sea surface temperatures. Fires were synchronous with La Niñas, cool phases of the Pacific Decadal Oscillation (PDO), and warm phases of the Atlantic Multidecadal Oscillation (AMO). These quasi-periodic circulation features are associated with drought conditions over much of the western United States. The opposite pattern (El Niño, warm PDO, cool AMO) was associated with fewer fires than expected. Regional tree recruitment largely occurred during wet periods in precipitation reconstructions, with the most abundant recruitment coeval with an extended pluvial from the late 1700s to early 1800s. Widespread even-aged cohorts likely were not the result of large crown fires causing overstory mortality, but rather were caused by optimal climate conditions that contributed to synchronous regional recruitment and longer intervals between surface fires. Synchronous recruitment driven by climate is an example of the Moran effect. The presence of abundant fire-scarred trees in multi-aged stands supports a prevailing historical model for ponderosa pine forests in which recurrent surface fires affected heterogenous forest structure, although the Black Hills apparently had a greater range of fire behavior and resulting forest structure over multi-decadal time scales than ponderosa pine forests of the Southwest that burned more often.

Chronology as Topic↗
PubMed2006

Simulating the influences of various fire regimes on caribou winter habitat.

Caribou are an integral component of high-latitude ecosystems and represent a major subsistence food source for many northern people. The availability and quality of winter habitat is critical to sustain these caribou populations. Caribou commonly use older spruce woodlands with adequate terrestrial lichen, a preferred winter forage, in the understory. Changes in climate and fire regime pose a significant threat to the long-term sustainability of this important winter habitat. Computer simulations performed with a spatially explicit vegetation succession model (ALFRESCO) indicate that changes in the frequency and extent of fire in interior Alaska may substantially impact the abundance and quality of winter habitat for caribou. We modeled four different fire scenarios and tracked the frequency, extent, and spatial distribution of the simulated fires and associated changes to vegetation composition and distribution. Our results suggest that shorter fire frequencies (i.e., less time between recurring fires) on the winter range of the Nelchina caribou herd in eastern interior Alaska will result in large decreases of available winter habitat, relative to that currently available, in both the short and long term. A 30% shortening of the fire frequency resulted in a 3.5-fold increase in the area burned annually and an associated 41% decrease in the amount of spruce-lichen forest found on the landscape. More importantly, simulations with more frequent fires produced a relatively immature forest age structure, compared to that which currently exists, with few stands older than 100 years. This age structure is at the lower limits of stand age classes preferred by caribou from the Nelchina herd. Projected changes in fire regime due to climate warming and/or additional prescribed burning could substantially alter the winter habitat of caribou in interior Alaska and lead to changes in winter range use and/or population dynamics.

Alaska↗
PubMed1975

Heart rate and ECG responses of fire fighters.

Data were obtained from 35 fire fighters responding to 189 alarms. Fifteen to 30 sec after an alarm heart rate showed a mean increase of 47 beats/min (range 12-117 beats/min). Approximately one minute after the alarm, while on the truck, heart rate still showed a mean increase of 30 beats/min (range 1 to 80 beats/min) above that recorded before alarm. S-T segment changes were observed in the ECG shortly after the alarm sounded. Upon approaching a fire, heart rates as high as 150 beats/min were observed before the men got off the fire truck. During actual fire fighting extremely high heart rates were observed for prolonged periods of time. One fire fighter had a mean heart rate of 188 beats/min for 15 minutes during the initial stages of a structure fire. The heart rate responses observed immediately after the alarm as well as on the truck approaching a fire indicate that the men experience a state of high anxiety. The extremely high heart rates observed for prolonged periods during fire fighting may also indicate a state of high anxiety coupled with the heavy work performed in a hot environment. Repeated exposure to states of high anxiety as well as inhaling pollutants related to the high incidence of ischemic-stress tests previously observed in fire fighters.

Adult↗
PubMedDate not supplied

Descriptive epidemiology of unintentional residential fire injuries in King County, WA, 1984 and 1985.

Although most studies have concentrated on fatal residential fire injuries, which are a leading cause of fatal injuries in the United States, few investigators have examined in detail nonfatal injuries as a consequence of residential fires. This population-based study used the Washington State Fire Incident Reporting System to assess the incidence and descriptive epidemiology of fatal and nonfatal burns or respiratory tract damage resulting from unintentional residential fires. For the 2-year period 1984-85 in King County, WA, the mortality rate due to injury in a residential fire was 0.7 per 100,000 per year, and the incidence of nonfatal injuries was 5.6 per 100,000 per year. Of 17 fatalities, 59 percent of the deaths occurred at the scene of the fire. Of 128 persons with nonfatal injuries, 19 percent were hospitalized; although the 55 percent seen as outpatients and the 26 percent treated by the fire department or paramedics at the fire scene usually had minor injuries, they would not have been captured if only traditional data sources had been employed. Those injured averaged 2.8 days of restricted activity, but the range was from less than 1 day to 1 year. Injuries were more common in the households with a low socioeconomic status and among nonwhites, especially American Indians. Variation in incidence by age, sex, and source of ignition for deaths and nonfatal injuries suggests appropriate targets for future fire injury prevention programs.

Age Factors↗
PubMed1980

Smoke detectors: reducing deaths and injuries due to fire.

The United States leads all nations in the incidence of deaths due to fire. In the past two decades significant technologic advances have resulted in the development of inexpensive and reliable smoke detectors. These detectors can provide early warning to allow sleeping residents easy exist when a fire ocfurs in the house. Currently, there are three major types of early warning devices: heat detectors, photoelectric smoke detectors, and ionization smoke detectors. Heat detectors sound an alarm in response to rapid increases in temperature and/or ambient temperatures above 135 F. Photoelectric smoke detectors are particularly effective for smoldering fires, because they are less influenced by the smaller particles of combustion emitted during household cooking or from automobile exhaust than are ionization smoke detectors. The ionization smoke detectors respond more quickly than photoelectric smoke detectors to fast burning fires and have been proved effective in sounding an early alarm in the vast majority of home fires. For best all-around fire protection, a home should have more than one type of detector. Detectors should be located on the ceiling or high on the ceiling of every level of the house close to each bedroom. Properly installed and maintained smoke detectors can reduce the tragic consequences of home fires, but even greater gains can be made by combining these early warning systems with a reduction in home fire hazards and in practicing a well planned fire escape route.

Fires↗
PubMed1997

Hyperbaric and hypobaric chamber fires: a 73-year analysis.

Fire can be catastrophic in the confined space of a hyperbaric chamber. From 1923 to 1996, 77 human fatalities occurred in 35 hyperbaric chamber fires, three human fatalities in a pressurized Apollo Command Module, and two human fatalities in three hypobaric chamber fires reported in Asia, Europe, and North America. Two fires occurred in diving bells, eight occurred in recompression (or decompression) chambers, and 25 occurred in clinical hyperbaric chambers. No fire fatalities were reported in the clinical hyperbaric chambers of North America. Chamber fires before 1980 were principally caused by electrical ignition. Since 1980, chamber fires have been primarily caused by prohibited sources of ignition that an occupant carried inside the chamber. Each fatal chamber fire has occurred in an enriched oxygen atmosphere (> 28% oxygen) and in the presence of abundant burnable material. Chambers pressurized with air (< 23.5% oxygen) had the only survivors. Information in this report was obtained from the literature and from the Undersea and Hyperbaric Medical Society's Chamber Experience and Mishap Database. This epidemiologic review focuses on information learned from critical analyses of chamber fires and how it can be applied to safe operation of hypobaric and hyperbaric chambers.

Atmosphere Exposure Chambers↗
PubMed1992

Repetitive firing properties in subpopulations of the chick Edinger Westphal nucleus.

The avian Edinger Westphal nucleus, through the ciliary ganglion, controls accommodation, iris constriction, and blood flow through the choroid. In live brainstem slices, the nucleus is easily identifiable as an olive-shaped cluster of neurons dorsal to the oculomotor nerve and nucleus. Intracellular recordings from neurons in the nucleus identified two classes of responses to sustained (300 to 500 ms) injections of depolarizing current. One set of cells fired action potentials for the duration of the pulse while a second set of cells fired action potentials only transiently, during the first 50 to 100 ms, after which they remained silent regardless of the size of the depolarization. Intracellular recordings followed by injections of the fluorescent dye lucifer yellow revealed that repetitively firing cells were located in the lateral half of the nucleus while non-repetitively or transiently firing cells were located in the medial half. These locations correspond to different Edinger Westphal subdivisions which have distinct inputs and target populations. The varying firing patterns are discussed with reference to the known functions of the subdivisions in which they occur. Replacement of calcium by magnesium in the extracellular medium had no effect on the number of action potentials fired by non-repetitively firing cells, suggesting that a calcium-activated potassium current is not responsible for suppressing repetitive firing in these cells. In contrast, in repetitively firing cells removal of extracellular calcium increased the frequency of action potential discharge and decreased the amplitude of afterhyperpolarizations following single action potentials. Addition of cadmium to the bath medium had similar effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1989

Peripheral induction of burst firing in locus coeruleus neurons by nicotine mediated via excitatory amino acids.

The effect of systemic nicotine administration (50 micrograms kg-1 i.v.) on the activity of brain noradrenaline neurons in the locus coeruleus (LC) of chloral hydrate-anesthetized rats was analyzed with single cell recording techniques and quantitative computer assessment of firing rate, degree of bursting, and regularity of firing. Nicotine caused an increased firing rate of the cells, with an average time of onset of 1.7 s. An increase in burst activity was observed, as well as deregularization of the firing pattern. Intraventricularly administered kynurenic acid (1 mumol), an antagonist of excitatory amino acids (EAA), did not change the firing rate of the LC cells, but did induce a marked regularization of their firing pattern into a pacemaker-like activity and completely abolish burst firing. The EAA antagonist also blocked all of the above effects of nicotine on the LC neurons as well as their typical burst-activation response to a peripheral, noxious stimulus such as paw-pinch. Since the circulation time in the rat is about 20 s, these results provide unequivocal evidence for a peripheral site of origin for the rapid LC activation induced by systemic nicotine administration. The data also allow the conclusion that the nicotine-induced LC activation is indirect and dependent on EAA in brain. Our results provide evidence for a tonically active EAA input to the LC, being of importance for induction of changes in the spontaneous, pacemaker activity of LC neurons into burst firing or more irregular firing patterns. It is suggested that the LC activation by nicotine may be significant in relation to tobacco dependence.

Action Potentials↗
PubMed1992

Iontophoretically administered drugs acting at the N-methyl-D-aspartate receptor modulate burst firing in A9 dopamine neurons in the rat.

Extracellular single-unit recording and iontophoresis were used to examine the effect of N-methyl-D-aspartate (NMDA) and the competitive NMDA antagonist (+/-)-4-(3-phosphonopropyl)-2-piperazine carboxylic acid (CPP) on the firing rate and firing pattern of A9 dopamine (DA) neurons in the rat. Administration of NMDA produced a dose-dependent increase in firing rate (up to nearly 300% of baseline at the highest ejection current), which could be blocked by iontophoretic CPP. Low currents (less than 10 nA) were sufficient to induce apparent depolarisation inactivation in some neurons. In addition to this effect on firing rate, NMDA also caused a dramatic increase in burst firing, which was also dose dependent; cells made more bursts, and each burst consisted of more spikes. The only measured aspect of burst morphology that was not affected was the mean burst interspike interval. All nonbursting cells (n = 10) were converted to burst firing by the drug. CPP administered alone was found to reduce burst firing, without affecting the firing rate. These data suggest that a tonically active excitatory amino acid input to A9 DA neurons is responsible for inducing burst firing in vivo and that this input seems to operate via the NMDA receptor, possibly by virtue of its link to a Ca2+ ionophore.

Animals↗