Estimates of Lifetime Risk of Occupational Fatal Injury from Age-Specific Rates

The lifetime risk of fatal workplace injury is a critical issue in the evaluation of occupational hazards. Recently, Fosbroke, Kisner, and Myers (1997) described a metric for working lifetime risk (WLTR) to determine the probability that a worker will die due to a work-related fatal injury in a year over a certain number of years of employment. This quantity was defined assuming that the annual rate of fatal injuries will be the same each year during employment. Recognizing the fact that annual fatal injury rates differ with the age of the worker along with other factors, modification of the definition of working lifetime risk is derived. We obtain the estimates of the lifetime risk using age-categorized annual fatality rates and derive an estimate of the standard error of the WLTR estimator and a confidence interval for the WLTR. We illustrate these calculations by estimating the lifetime risk for work-related fatal injuries for workers in four high risk industries: agriculture-forestry-fishing, mining, construction, and transportation public utilities. The estimates are based on employment data from the Bureau of Labor Statistics and an updated version of fatality data from the National Traumatic Occupational Fatalities surveillance system.     

Focus: Preventive Medicine: Firearm Injury Among Children and Adolescents in Nigerian Civilian Trauma Setting: Prevalence,Pattern, and Implications for Prevention

Firearm injury in children and adolescents and the morbidity associated with it is an appreciable burden in resource-limited settings, though it is under-reported. This study aimed to determine its prevalence and pattern in Nigerian civilian trauma setting. We undertook a retrospective study of all the patients with firearm injury aged 19 years or under who visited the Emergency Department (ED) of two tertiary hospitals in Nigeria over a period of 15 years. Of the 46,734 children and adolescents seen in the ED, firearm injury was the reason for the visit in 56 of them, giving a prevalence of 1.2 per 1000 ED attendance (95% CI: 0.9-1.6). The male-to-female ratio was 1.8:1, and the mean age was 13.98 ± 5.6 years. The preponderance of firearm injury was in the rural areas, during the dry season, at home, and in the daytime. Armed robbery (20, 35.7%) and communal clash (7, 12.5%) were the two topmost incidents leading to gunshot wounds. Armed robbery-related gunshot occurred mostly on the roads and at nighttime and involved predominantly 15-19-year-olds. Lower extremity was the topmost anatomical region involved. The majority (67%) had no pre-hospital care; the mean and median injury-hospital arrival interval respectively was 352 hrs and 4.2 hrs. Wound infection was the topmost complication. The mean hospital length of stay was 22.6 days. One (1.8%) of the patients died on the third day of hospital admission. Educational campaigns for prevention intensified during the dry season should highlight the risk of firearm injury to this age group and emphasize the importance of proper supervision and guidance of vulnerable children and adolescents. Improving the rates of pre-hospital care and early presentation of victims to the hospital should be considered in tertiary injury prevention strategies.     

Limited Supermarket Availability Is Not Associated With Obesity Risk Among Participants in the Kansas WIC Program

Socioecological theory and a growing body of research suggests that geographic, racial, ethnic, and socioeconomic disparities in the prevalence of obesity are linked to disparities in the availability of food retail outlets that provide healthy food options. We examined the availability of food stores for low‐income women in Kansas and tested whether food store availability was associated with obesity using cross‐sectional, geocoded data from women participating in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) (n = 21,166) in Kansas. The availability and density of food stores within a 1, 3, and 5 mile radius of residence was determined, and multivariate logistic regression was used to examine the association of food store availability with obesity. The availability of convenience, grocery stores, and supermarkets varied across the urban–rural continuum, but the majority of WIC recipients lived within a 1 mile radius of a small grocery store. WIC participants in micropolitan areas had the greatest availability of food stores within a 1 mile radius of residence. Availability and density of food stores was not associated with obesity in metropolitan and rural areas, but availability and density of any type of food store was associated with an increased risk of obesity among WIC recipients in micropolitan areas. These results suggest that limited spatial availability of grocery stores and supermarkets does not contribute to obesity risk among low‐income WIC recipients in Kansas, and that urban influence moderates the contribution of food environments to obesity.     

Lifetime Risk of Fatal Occupational Injuries within Industries,by Occupation,Gender, and Race

Estimates of risk accumulated over a working lifetime are used to assess the significance of many workplace health hazards. Most studies which have estimated this risk have focused on a worker's lifetime risk of dying of a stated illness based on exposure to a hazard in a specific job. The concept, however, has not been widely applied to occupational injury deaths. This study examines the use of lifetime risk based on national fatal injury data from the Bureau of Labor Statistics (BLS) Census of Fatal Occupational Injuries (CFOI). Lifetime risks are defined by specific causal events for those groups identified as having the highest general lifetime risks. The lifetime risk model for injury used in this work can be compared with risk assessments for occupational illnesses. Fatal injury lifetime risk estimates will be useful in defining traumatic injury exposures that are appropriate for targeting research and prevention efforts needed to reduce the burden of work-related death within the United States. These estimates also provide a means of prioritizing traumatic injury research with fatal illness research, while providing the additional benefit of providing a means of informing workers of their fatal injury risks.     

Work-Related Fatal-Injury Risk of Construction Workers by Occupation and Cause of Death

To assess cause- and occupation-specific risks of work related fatal injuries among U.S. construction workers, the National Traumatic Occupational Fatalities (NTOF) surveillance system and Current Population Survey were used to obtain injury and employment data for the years 1990 through 1994. Risks were assessed by both rate and working lifetime risk. The occupation found to have the highest fatal-injury rate in construction was electrical-power installers and repairers (96.6 deaths/100,000 workers), followed by structural-metal workers (86.4) and operating engineers (41.0). The occupation found to have the largest numbers of fatalities was construction laborers (1133 deaths), followed by carpenters (408), and construction supervisors (392). The leading causes of death varied by occupation. Construction in general has experienced a decline in fatal-injury rates over the years; however, this decline did not occur equally across occupations and causes of death. The presentation of working lifetime injury risks provides a measure of risk for occupational injuries that can be compared with occupational illness risk assessments. This study is the first to provide a comprehensive national profile of work-related fatal-injury risks among United States construction workers by occupation and cause of death. The results will be useful in focusing research and prevention efforts on specific hazards in high-risk construction occupations.     

Stored-product insects associated with a retail pet store chain in Kansas

The types and numbers of insect species associated with eight Kansas retail stores belonging to a pet store chain were surveyed during February to August 2001. Insects were monitored at 1-3-wk intervals using food- and pheromone-baited pitfall traps for beetles and pheromone-baited sticky traps for moths. Thirty traps of each type were placed within a store. Thirty insect species belonging to 20 families in four orders were recorded from the eight stores. The weevils, Sitophilus spp.; Indianmeal moth, Plodia interpunctella (Hübner); and merchant grain beetle, Oryzaephilus mercator (Fauvel), were the most common and abundant species in all stores, whereas the red-legged ham beetle, Necrobia rufipes (Degeer), and red flour beetle, Tribolium castaneum (Herbst), were abundant only in one store. The numbers of each insect species captured varied from store to store. In each of the stores, a total of 12-19 stored-product species were captured in traps, and seven of the eight stores had relatively high species diversity. With the exception of one store, the different types of insect species found among the remaining seven stores were essentially similar. The mean density of insects in infested bulk-stored and bagged pet food products removed from a store ranged from 65 to 656 adults/kg. The types and numbers of insect species captured in traps indicated that infestations were well established in the surveyed stores. Early detection and management of these infestations is critical for maintaining quality and integrity of food products sold in the pet stores.     

Effects of lifetime exposure to shiftwork on fitness for duty in police officers

Aging and demographic changes in Europe and other global economies have led to a discussion about postponing the legal retirement age; however, health and safety consequences for the workforce have not yet been examined. Thus, the aim of this study was to investigate the effects of lifetime exposure to shiftwork on health impairments and fitness for duty. Two samples of the police force from one of the states of the Federal Republic of Germany were used. One sample was collected in 2008-2009 with a self-administered Internet questionnaire (n = 705); the other sample was derived from employment records provided by the police force of the same federal state for the years 2002-2009 (n = 2460). Both samples contained information about the number of years worked in shiftwork across the entire working life and impairments to fitness for duty assessed by occupational physicians. Thus, the number of years of shiftwork until the diagnosis of the first reduction in fitness for duty could be calculated. Survival analyses were performed to estimate the risk (hazard rate) for experiencing a reduction in fitness for duty across lifetime exposure to shiftwork in years, controlling for age, sex, work type, and police district. Hazard estimates were compared across both samples to cross-validate the results. The findings indicated an increase in the risk of reduced fitness for duty with increasing number of years in shiftwork during the working life in both samples. The hazard rates followed an exponential trend, indicating a rapid increase in health impairments in particular beyond 20 yrs of shiftwork. These findings were consistent in both samples, collected with different methods and over different time periods, thus indicating high validity. Therefore, occupational stress factors, such as exposure to shiftwork, need to be taken into account when discussing the postponement of the legal retirement age.     

Effects of Lifetime Exposure to Shiftwork on Fitness for Duty in Police Officers

Aging and demographic changes in Europe and other global economies have led to a discussion about postponing the legal retirement age; however, health and safety consequences for the workforce have not yet been examined. Thus, the aim of this study was to investigate the effects of lifetime exposure to shiftwork on health impairments and fitness for duty. Two samples of the police force from one of the states of the Federal Republic of Germany were used. One sample was collected in 2008–2009 with a self-administered Internet questionnaire (n?=?705); the other sample was derived from employment records provided by the police force of the same federal state for the years 2002–2009 (n?=?2460). Both samples contained information about the number of years worked in shiftwork across the entire working life and impairments to fitness for duty assessed by occupational physicians. Thus, the number of years of shiftwork until the diagnosis of the first reduction in fitness for duty could be calculated. Survival analyses were performed to estimate the risk (hazard rate) for experiencing a reduction in fitness for duty across lifetime exposure to shiftwork in years, controlling for age, sex, work type, and police district. Hazard estimates were compared across both samples to cross-validate the results. The findings indicated an increase in the risk of reduced fitness for duty with increasing number of years in shiftwork during the working life in both samples. The hazard rates followed an exponential trend, indicating a rapid increase in health impairments in particular beyond 20 yrs of shiftwork. These findings were consistent in both samples, collected with different methods and over different time periods, thus indicating high validity. Therefore, occupational stress factors, such as exposure to shiftwork, need to be taken into account when discussing the postponement of the legal retirement age. (Author correspondence: anna.wirtz@gawo-ev.de)     

Occupational Risks and Exposures Among Wildlife Health Professionals

Most emerging infectious diseases are zoonotic in origin, with wildlife a frequent source of zoonotic disease events. Although individuals with extensive wildlife contact may be at the greatest risk of contracting novel infectious agents, the occupational risk of those working closely with wildlife has not been well studied. This study assessed the occupational exposures among wildlife health professionals working in multiple countries worldwide. An occupational risk survey of past and present exposures was developed and administered online in a confidential manner to wildlife workers recruited through an ongoing international wildlife pathogen surveillance project. Surveys were completed by 71 participants in 14 countries. Significant lifetime exposures reported included bites from bats and rodents and touching dead animals. Completion of training in occupational safety was reported by 75% of respondents. While gloves were used for most tasks, use of N95 respirators and other personal protective equipment varied by task. Eighty percent of workers reported rabies vaccination. Some respondents indicated interest in enhanced occupational health services targeting their unique needs. Wildlife workers represent an occupational population at risk of zoonotic infection and injury. Enhanced occupational health services targeting wildlife workers could reduce the risk and sequelae of zoonotic exposure and infection.     

Validity of Using Background Leukemia Incidence Rates with Cohort Mortality-Based Potency Estimates to Calculate Excess Lifetime Risk

Data from occupational cohort mortality studies have been used to derive exposure-response curves and general population excess lifetime cancer risks, given low-level, chronic exposure. Using an actuarial method, mortality-based rate ratios associated with cumulative exposures are applied to age-specific background cancer mortality rates for a theoretical population aged birth to 70 years. In one recent U.S. Environmental Protection Agency health assessment, a mortality-based leukemia relative rate model was used with background leukemia incidence rates, rather than mortality rates, to calculate excess lifetime risk of leukemia incidence. We examined the validity and implications of this novel approach, while considering possible bias if a potential leukemogen did not pose equal risk by cell type. Limited sensitivity analyses were also conducted. Our analyses show that using total leukemia mortality-based potency estimates with background incidence rates will introduce a biased estimate of excess lifetime risk, the direction of which varies by potency and the histological type of leukemia. These biases were somewhat increased on adjustment for possible greater susceptibility of children. For potent carcinogens, the traditional approach provides a reasonable approximation of excess lifetime mortality risk for both the more and less fatal forms of leukemia, even after adjustments for children and is, therefore, to be preferred. Less consistency by leukemia cell type and background rate was observed for flatter exposure-response curves. This evaluation illustrates the importance of carefully examining the impact of methodological changes to calculations of excess lifetime risk before implementation.     

Occupational Injuries in Germany: Population-Wide National Survey Data Emphasize the Importance of Work-Related Factors

Unintentional injuries cause much of the global mortality burden, with the workplace being a common accident setting. Even in high-income economies, occupational injury figures remain remarkably high. Because risk factors for occupational injuries are prone to confounding, the present research takes a comprehensive approach. To better understand the occurrence of occupational injuries, sociodemographic factors and work- and health-related factors are tested simultaneously. Thus, the present analysis aims to develop a comprehensive epidemiological model that facilitates the explanation of varying injury rates in the workplace. The representative phone survey German Health Update 2010 provides information on medically treated occupational injuries sustained in the year prior to the interview. Data were collected on sociodemographics, occupation, working conditions, health-related behaviors, and chronic diseases. For the economically active population (18–70 years, n = 14,041), the 12-month prevalence of occupational injuries was calculated with a 95% confidence interval (CI). Blockwise multiple logistic regression was applied to successively include different groups of variables. Overall, 2.8% (95% CI 2.4–3.2) of the gainfully employed population report at least one occupational injury (women: 0.9%; 95% CI 0.7–1.2; men: 4.3%; 95% CI 3.7–5.0). In the fully adjusted model, male gender (OR 3.16) and age 18–29 (OR 1.54), as well as agricultural (OR 5.40), technical (OR 3.41), skilled service (OR 4.24) or manual (OR 5.12), and unskilled service (OR 3.13) or manual (OR 4.97) occupations are associated with higher chances of occupational injuries. The same holds for frequent stressors such as heavy carrying (OR 1.78), working in awkward postures (OR 1.46), environmental stress (OR 1.48), and working under pressure (OR 1.41). Among health-related variables, physical inactivity (OR 1.47) and obesity (OR 1.73) present a significantly higher chance of occupational injuries. While the odds for most work-related factors were as expected, the associations for health-related factors such as smoking, drinking, and chronic diseases were rather weak. In part, this may be due to context-specific factors such as safety and workplace regulations in high-income countries like Germany. This assumption could guide further research, taking a multi-level approach to international comparisons.     

Will Risks to Older Workers Change in the 21st Century?

Workers aged 65 and older face different risks than those in younger age groups. The occupational fatality rate for this group (13.6 per 100,000 workers) during 1980-1995 was almost three times greater than the rate for workers aged 16 to 64. This study projects the traumatic occupational fatality experience for the ten occupations with the largest number of occupational fatalities for workers 65 years and older. Although the occupational fatality rate for workers 65 years and older is projected to decrease from 12.5 in 1995 to 11.5 in year 2008, the number of occupational fatalities for this group is projected to increase from 459 in 1995 to 518 in year 2008. The overall proportion of occupational fatalities experienced by workers in the 65 years and older age group is expected to increase from 7% in 1995 to 10% in 2008. To assist in developing the most effective interventions, the five leading external causes of death associated with these fatalities were estimated for year 2008. With the aging of the American workforce, more research is needed in areas concerned with protecting older workers from injury.     

Factors Associated with Occupational Needle Stick and Sharps Injuries among Hospital Healthcare Workers in Bale Zone,Southeast Ethiopia

Background

Needle stick and sharps injuries are occupational hazards to healthcare workers. Every day healthcare workers are exposed to deadly blood borne pathogens through contaminated needles and other sharp objects. About twenty blood borne pathogens can be transmitted through accidental needle stick and sharp injury. The study was conducted to determine the lifetime and past one year prevalence of needle stick and sharps injuries and factors associated with the past one year injuries among hospital healthcare workers in Southeast Ethiopia.

Methods

An institutional based cross sectional study was conducted in December 2014 among healthcare workers in four hospitals of Bale zone, Southeast of Ethiopia. A total of 362 healthcare workers were selected randomly from each department in the hospitals. Data were collected using self-administered questionnaire. The collected data were entered into Epi-Info version 3.5 and analyzed using SPSS version 20.0. Multivariable logistic regression analysis was used to identify the independent effect of each independent variable on the outcome variable. Written informed consent was secured from the participants.

Results

The prevalence of lifetime needle stick and sharp injury was 37.1% with 95% CI of 32.0% to 42.5%. The prevalence of injury within the past one year was 19.1% with 95% CI of 14.9% to 23.3%. Emergency ward was a department with highest needle stick and sharp injury (31.7%). The main cause of injury was syringe needles (69.8%). Participants who practiced needle recapping had higher odds of needle stick and sharp injury within the past 12 months (AOR = 3.23, 95% CI: 1.78, 5.84) compared to their counterparts.

Conclusions

Nearly one out of five respondents had experienced needle stick and/or sharp injury at least once within past one year. There were practices and behaviors that put healthcare workers at risk of needle stick and sharp injury at the study area. Needle recapping was key modifiable risk behavior. Health policy makers and hospital administrators should formulate strategies to improve the working condition for healthcare workers and increase their adherence to universal precautions.     

Factors Associated with Fatal Occupational Accidents among Mexican Workers: A National Analysis

Objective

To identify the factors associated with fatal occupational injuries in Mexico in 2012 among workers affiliated with the Mexican Social Security Institute.

Methods

Analysis of secondary data using information from the National Occupational Risk Information System, with the consequence of the occupational injury (fatal versus non-fatal) as the response variable. The analysis included 406,222 non-fatal and 1,140 fatal injuries from 2012. The factors associated with the lethality of the injury were identified using a logistic regression model with the Firth approach.

Results

Being male (OR=5.86; CI95%: 4.22-8.14), age (OR=1.04; CI95%: 1.03-1.06), employed in the position for 1 to 10 years (versus less than 1 year) (OR=1.37; CI95%: 1.15-1.63), working as a facilities or machine operator or assembler (OR: 3.28; CI95%: 2.12- 5.07) and being a worker without qualifications (OR=1.96; CI95%: 1.18-3.24) (versus an office worker) were associated with fatality in the event of an injury. Additionally, companies classified as maximum risk (OR=1.90; CI 95%: 1.38-2.62), workplace conditions (OR=7.15; CI95%: 3.63-14.10) and factors related to the work environment (OR=9.18; CI95%:4.36-19.33) were identified as risk factors for fatality in the event of an occupational injury.

Conclusions

Fatality in the event of an occupational injury is associated with factors related to sociodemographics (age, sex and occupation), the work environment and workplace conditions. Worker protection policies should be created for groups with a higher risk of fatal occupational injuries in Mexico.     

Sickness absence and shift work among Japanese factory workers

To investigate the effect of shift work on long-term sickness absence (more than 7 calendar days), an 8-year follow-up study was carried out in a factory in Japan. The participants were male employees aged 18-54 years who were engaged in manufacturing sites. Shift patterns were classified by the number of non-daytime working days during the previous one-year. The causes of sickness absence were classified into three groups, 1) causes except injury, diseases of the musculoskeletal system and connective tissue, 2) injury, 3) diseases of the musculoskeletal system and connective tissue. The analysis of long-term sickness absences was based on the first occurrence. The age-adjusted incidence of sickness absence among shift workers who were on non-daytime shifts more than two-thirds of working days during the previous one year was significantly higher than that among other workers. After adjusting for confounding factors, a significant high risk still existed for this group of workers taking sickness absence for all causes and causes except for injury and the musculoskletal disorders. These findings suggest that shift workers who are engaged on a particular shift schedule are more likely to take leave due to sickness.     

Different Occupations Associated with Amyotrophic Lateral Sclerosis: Is Diesel Exhaust the Link?

The cause of sporadic amyotrophic lateral sclerosis (SALS) remains unknown. We attempted to find out if occupational exposure to toxicants plays a part in the pathogenesis of this disease. In an Australia-wide case-control study we compared the lifetime occupations of 611 SALS and 775 control individuals. Occupations were coded using country-specific as well as international classifications. The risk of SALS for each occupation was calculated with odds ratios using logistic regression. In addition, the literature was searched for possible toxicant links between our findings and previously-reported occupational associations with SALS. Male occupations in our study that required lower skills and tasks tended to have increased risks of SALS, and conversely, those occupations that required higher skills and tasks had decreased risks of SALS. Of all the occupations, only truck drivers, where exposure to diesel exhaust is common, maintained an increased risk of SALS throughout all occupational groups. Another large case-control study has also found truck drivers to be at risk of SALS, and almost two-thirds of occupations, as well as military duties, that have previously been associated with SALS have potential exposure to diesel exhaust. In conclusion, two of the largest case-control studies of SALS have now found that truck drivers have an increased risk of SALS. Since exposure to diesel exhaust is common in truck drivers, as well as in other occupations that have been linked to SALS, exposure to this toxicant may underlie some of the occupations that are associated with SALS.     

Determination of polycyclic aromatic hydrocarbons in ambient particulate matter PM2.5 and 1-hydroxypyrene in children from an area near an oil refinery in Northeast Mexico

Exposure to polycyclic aromatic hydrocarbons (PAHs) has been associated with carcinogenic and mutagenic effects. Urban areas characteristically have high concentrations of PAHs associated with vehicle traffic and industry; among these oil refining stands out. One of the six refineries in Mexico has operated in the Metropolitan Area of Monterrey since 1979. The objective of this study was to evaluate exposure to PAHs by determining 1-hydroxypyrene (1-OHP) concentration in children living in an urban area near an oil refinery as well as to determine the relative health risk by exposure to PAHs in this population. This study included 90 children of both sexes aged 5–12 years. Two urine samples were collected, one in summer and one in winter to determine urinary 1-OHP. At the same time, the concentrations of PAHs associated with PM_2.5 were collected in the study area. The mean concentration of 1-OHP was 0.14 μmol/mol of creatinine. Twelve PAHs were quantified, seven are potential carcinogenics and one (benzo[a]pyrene) is carcinogenic for humans, and used as an indicator of cancer relative risk from exposure to PAHs. The annual average concentration of benzo[a]pyrene suggest an excess lifetime cancer risk of 1/100,000 habitants, in the study area.     

A Graphical Analysis of Mortality Rates and Years of Potential Life Lost

One challenge in assessing occupational fatal injuries is choosing a summary measure of the impact of these injuries. Each metric emphasizes different aspects of health risk, and fatal injury reports often focus on only one summary measure at a time. Deaths from the National Traumatic Occupational Fatality database were combined into external cause of death (e-code) groups. Graphs comparing average years of potential life lost (YPLL), mortality rate, and their product, “YPLL-rate”, are presented for e-code groups overall, industries and occupations, and e-code groups within selected industries and occupations. This integrated analysis of fatal injury characteristics allows identification of the portion of the workforce at highest risk. Homicides and electrocutions (e-code groups) had high mortality rates, average YPLL, and YPLL-rates, both overall, and within several of the industries and occupations examined. The industry and occupation of Agriculture, Forestry, and Fishing experienced a very high mortality rate and the lowest average YPLL for both industries and occupations. Laborer was the most hazardous occupation for young workers with an average YPLL near 40, and a mortality rate greater than 15 deaths per 100,000 worker-years.     

Adaptation in auditory-nerve fibers: A revised model

Adaptation of firing rates in auditory-nerve fibers appears to reflect two distinct processes. Rapid adaptation occupies the first few milliseconds of response and is superimposed upon short-term adaptation which has a time constant of about 40 ms. The properties of the two processes are reviewed and compared, and a phenomenological model is developed that successfully accounts for them. The model consists of several stages which have been tentatively associated with underlying physiological processes. In the first stage stimulus intensity is transformed by a static nonlinearity, followed by a low-pass filter. The filtered output may correspond to the hair-cell receptor potential. It modulates the release of a substance that possibly represents synaptic transmitter. Adaptation is produced by the depletion of transmitter which is located in three stores in cascade. A global store with fixed concentration controls the steady-state response and replenishes a local store which is responsible for short-term adaptation. The local store seplenishes a rapidly depleted immediate store. Flow between stores is proportional to concentration gradients with the following exceptions. The immediate store is subdivided into independent volumes or sites and there is no flow among sites or back to the local store. A given site becomes activated only when the receptor potential exceeds its particular activation value and the number of activated sites is proportional to the receptor potential. The flow of transmitter from the immediate store is assumed to be proportional to neural firing rate, with some minor modifications described in the text. The properties of the model are determined from the underlying equations and from a computer simulation. The model produces realistic response properties including PST histograms, onset and steady-state rate-intensity functions, incremental and decremental responses, response modulation for amplitude modulated stimuli, and period histograms for low-frequency tones.