Journal Reviews

Genaidy AM, Karwowski W, Christensen DM, et al. What is `heavy'? Ergonomics 1998; 41:420-432.

Workers often are instructed to ask for help in lifting an item if it is heavy, but what exactly do most people think of as "heavy"? These researchers from the University of Cincinnati and the University of Louisville (KY) sought to answer that question by studying 20 male and 20 female workers in the package delivery industry. All of the participants were experienced in package delivery and had received training in safe lifting techniques, which included instructions to seek help with heavy items.

Each employee was asked what amount of weight they would consider to fit 10 descriptions, ranging from "negligible" to "maximum" weights. The results showed that there were no differences between male and female answers for the "negligible" up to "somewhat heavy," the sixth point on the scale. But for the highest four categories, males used higher numbers.

The researchers note that the National Institute for Occupational Safety and Health recommends 23 kg as the maximum load that can be handled safely by the majority of the work force, but the study participants considered 23 kg to be only "somewhat heavy."The 40 kg that used to be the NIOSH limit before 1993 would be considered "very heavy" according to the study results.

The study results suggest that the typical worker can handle more of a "heavy" load than might be indicated by many previous studies, the researchers say. A "moderate" level of load heaviness, 14 kg, can be handled by 85% of the population, they say. t

Journal Reviews

Kuller R, Thorbjorn L. The impact of flicker from fluorescent lighting on well-being, performance and physiological arousal. Ergonomics 1998; 41:433-447.

The invisible flicker inherent in fluorescent lighting may adversely affect workers' speed and accuracy, according to this research from Sweden.

Fluorescent tubes are by far the dominant light source in workplaces all over the world, and it has long been suspected that the flicker from fluorescent tubes may cause undue stress, especially when there is no additional sunlight. The flicker is caused by the way the light emitted from a fluorescent tube is based on electrical discharges, modulated in synchrony with the power supply. Previous research has established that the flicker, mostly unseen to the eye, may influence brain wave patterns.

The researchers studied 39 subjects in a simulated office environment, with the men and women performing common office tasks such as reading and filling out forms. The participants' brain wave patterns were measured as they worked under fluorescent lighting powered by conventional ballasts, and then under fluorescent lighting powered by high-frequency ballasts. The subjects reported that the perceived flicker was very low with both lighting systems, but they slightly favored the high-frequency ballasts.

There were no measurable differences in visual comfort, headache, and the feelings of stress or fatigue. The researchers also determined that some individuals are much more sensitive to the flicker than others, and these people may be affected adversely by the flicker found in the most common type of fluorescent tubes with conventional ballasts. Even if they do not consciously perceive the flicker, it may cause them to work less efficiently. To alleviate the stress, the researchers recommend using fluorescent light sources that are powered by high-frequency ballasts of good quality. t

Journal Reviews

Theorell T, Akizumi T, Hallquist J, et al. Decision latitude, job strain, and myocardial infarction: A study of working men in Stockholm. Amer J Public Health 1998; 382-389.

Blue-collar workers who have a lot of job stress and feel they have little ability to control their own work situation are at significantly increased risk of having an early heart attack, according to this study from Sweden.

The study involved 1,047 men who had a first heart attack between the ages of 45 and 64 years and who had worked full-time for the five years before the heart attack. The researchers questioned the men, or a surviving relative if the heart attack was fatal, about their job responsibilities, work history, psychological job demands, and their ability to make decisions on the job. Other factors that could contribute to the heart attack risk, such as high cholesterol and high blood pressure, also were investigated.

Those most vulnerable to heart attacks shared common factors, including decreased job status, a lowered level of decision making, and an inability to voice their opinions on the job. Those factors had a significant effect only on the men ages 45 to 54, not on the workers ages 55 to 64. The researchers theorize that the factors may not affect older men because they expect decreasing job status as they approach retirement age.

The findings of the study may be especially applicable to workers who have been downsized in their careers, or forced to accept a job of lower status than they are used to. Many heart attacks occur within a few years of such a negative job change, the study shows. t

Journal Reviews

Griffin MJ. Evaluating the effectiveness of gloves in reducing the hazards of hand-transmitted vibration. Occup Environ Med 1998; 55:340-348.

The commonly used measure of how well gloves can reduce the hazard of hand- transmitted vibration may not be reliable, according to this research from the University of Southamptom, England. The International Standard 10819 defines a method for the measurement of glove dynamic performance and specifies the performance requirements for anti-vibration gloves.

This researcher studied a number of gloves that were rated as anti-vibration gloves based on the international standard, but he found that the effectiveness of the gloves in reducing the vibration hazard were related to the vibration frequency of the tool. Some tools vibrate at a much higher frequency than other tools, and the international standard does not take that into consideration.

The gloves had little effect on the transmission of vibration to the hand from most of the tools. The gloves were useful only with tools that transmitted high-frequency vibration. The researcher concludes that the international standard "does not provide a convenient or sufficient means of evaluating the vibration isolation performance of gloves. The standard can classify a glove as an anti-vibration glove when it provides no useful attenuation of vibration on the handle of a tool, whereas a glove which does provide useful attenuation of vibration on a specific tool can fail the test." t

Journal Reviews

Centers for Disease Control and Prevention. Silicosis deaths among young adults - United States, 1968-1994. MMWR 1998; 47;331-335.

Young adults continue to die from silicosis at an alarming rate even though overall deaths from silicosis are on the decline, say researchers at the federal Centers for Disease Control and Prevention n Atlanta. Silicosis is a chronic disease caused by occupational exposure to inhaled crystalline silica dust.

The annual deaths from silicosis declined from 1,157 in 1968 to 400 in 1980, but the decline has been smaller among young adults. With younger workers, construction exposures accounted for 28% of deaths. None were related to mining, as often is the case with older workers. Twenty-one percent of silicosis deaths among older workers can be traced to mining exposures, but only 9.5% are related to construction.

Construction workers develop silicosis when they inhale silica that is used in sandblasting. The lung tissue reacts to the particles by surrounding them with hard nodules and scar tissue, causing shortness of breath and other symptoms.