Exposure to loud noise continues to be the largest cause of hearing loss in the adult population. The problem of NIHL impacts a number of disciplines. US standards for permissible noise exposure were originally published in 1968 and remain largely unchanged today. Indeed, permissible noise exposure for US personnel is significantly greater than that allowed in numerous other countries, including for example, Canada, China, Brazil, Mexico, and the European Union. However, there have been a number of discoveries and advances that have increased our understanding of the mechanisms of NIHL. These advances have the potential to impact how NIHL can be prevented and how our noise standards can be made more appropriate.
In the Occupational Safety and Health Act of 1970, Congress declared that its purpose was to assure, so far as possible, safe and healthful working conditions for every working man and woman and to preserve our human resources. In this Act, the National Institute for Occupational Safety and Health (NIOSH) is charged with recommending occupational safety and health standards and describing exposure concentrations that are safe for various periods of employment-including but not limited to concentrations at which no worker will suffer diminished health, functional capacity, or life expectancy as a result of his or her work experience. By means of criteria documents, NIOSH communicates these recommended standards to regulatory agencies (including the Occupational Safety and Health Administration [OSHA]) and to others in the occupational safety and health community. Criteria documents provide the scientific basis for new occupational safety and health standards. These documents generally contain a critical review of the scientific and technical information available on the prevalence of hazards, the existence of safety and health risks, and the adequacy of control methods. In addition to transmitting these documents to the Department of Labor, NIOSH also distributes them to health professionals in academic institutions, industry, organized labor, public interest groups, and other government agencies. In 1972, NIOSH published Criteria for a Recommended Standard: Occupational Exposure to Noise, which provided the basis for a recommended standard to reduce the risk of developing permanent hearing loss as a result of occupational noise exposure [NIOSH 1972]. NIOSH has now evaluated the latest scientific information and has revised some of its previous recommendations. The 1998 recommendations go beyond attempting to conserve hearing by focusing on preventing occupational noise-induced hearing loss (NIHL). This criteria document reevaluates and reaffirms the recommended exposure limit (REL) for occupational noise exposure established by the National Institute for Occupational Safety and Health (NIOSH) in 1972. The REL is 85 decibels, A-weighted, as an 8-hr time-weighted average (85 dBA as an 8-hr TWA). Exposures at or above this level are hazardous. By incorporating the 4000-Hz audiometric frequency into the definition of hearing impairment in the risk assessment, NIOSH has found an 8% excess risk of developing occupational noise-induced hearing loss (NIHL) during a 40-year lifetime exposure at the 85-dBA REL. NIOSH has also found that scientific evidence supports the use of a 3-dB exchange rate for the calculation of TWA exposures to noise. The recommendations in this document go beyond attempts to conserve hearing by focusing on prevention of occupational NIHL. For workers whose noise exposures equal or exceed 85 dBA, NIOSH recommends a hearing loss prevention program (HLPP) that includes exposure assessment, engineering and administrative controls, proper use of hearing protectors, audiometric evaluation, education and motivation, recordkeeping, and program audits and evaluations. Audiometric evaluation is an important component of an HLPP. To provide early identification of workers with increasing hearing loss, NIOSH has revised the criterion for significant threshold shift to an increase of 15 dB in the hearing threshold level (HTL) at 500, 1000, 2000, 3000, 4000, or 6000 Hz in either ear, as determined by two consecutive tests. To permit timely intervention and prevent further hearing losses in workers whose HTLs have increased because of occupational noise exposure, NIOSH no longer recommends age correction on individual audiograms.
Millions of Americans experience some degree of hearing loss. The Social Security Administration (SSA) operates programs that provide cash disability benefits to people with permanent impairments like hearing loss, if they can show that their impairments meet stringent SSA criteria and their earnings are below an SSA threshold. The National Research Council convened an expert committee at the request of the SSA to study the issues related to disability determination for people with hearing loss. This volume is the product of that study. Hearing Loss: Determining Eligibility for Social Security Benefits reviews current knowledge about hearing loss and its measurement and treatment, and provides an evaluation of the strengths and weaknesses of the current processes and criteria. It recommends changes to strengthen the disability determination process and ensure its reliability and fairness. The book addresses criteria for selection of pure tone and speech tests, guidelines for test administration, testing of hearing in noise, special issues related to testing children, and the difficulty of predicting work capacity from clinical hearing test results. It should be useful to audiologists, otolaryngologists, disability advocates, and others who are concerned with people who have hearing loss.
The Institute of Medicine carried out a study mandated by Congress and sponsored by the Department of Veterans Affairs to provide an assessment of several issues related to noise-induced hearing loss and tinnitus associated with service in the Armed Forces since World War II. The resulting book, Noise and Military Service: Implications for Hearing Loss and Tinnitus, presents findings on the presence of hazardous noise in military settings, levels of noise exposure necessary to cause hearing loss or tinnitus, risk factors for noise-induced hearing loss and tinnitus, the timing of the effects of noise exposure on hearing, and the adequacy of military hearing conservation programs and audiometric testing. The book stresses the importance of conducting hearing tests (audiograms) at the beginning and end of military service for all military personnel and recommends several steps aimed at improving the military services' prevention of and surveillance for hearing loss and tinnitus. The book also identifies research needs, emphasizing topics specifically related to military service.
Topics covered include fundamentals of sound, vibration and hearing, elements of a hearing conservation program, noise interference and annoyance, regulations, standards and laws.
The brain is the most complex organ in our body. Indeed, it is perhaps the most complex structure we have ever encountered in nature. Both structurally and functionally, there are many peculiarities that differentiate the brain from all other organs. The brain is our connection to the world around us and by governing nervous system and higher function, any disturbance induces severe neurological and psychiatric disorders that can have a devastating effect on quality of life. Our understanding of the physiology and biochemistry of the brain has improved dramatically in the last two decades. In particular, the critical role of cations, including magnesium, has become evident, even if incompletely understood at a mechanistic level. The exact role and regulation of magnesium, in particular, remains elusive, largely because intracellular levels are so difficult to routinely quantify. Nonetheless, the importance of magnesium to normal central nervous system activity is self-evident given the complicated homeostatic mechanisms that maintain the concentration of this cation within strict limits essential for normal physiology and metabolism. There is also considerable accumulating evidence to suggest alterations to some brain functions in both normal and pathological conditions may be linked to alterations in local magnesium concentration. This book, containing chapters written by some of the foremost experts in the field of magnesium research, brings together the latest in experimental and clinical magnesium research as it relates to the central nervous system. It offers a complete and updated view of magnesiums involvement in central nervous system function and in so doing, brings together two main pillars of contemporary neuroscience research, namely providing an explanation for the molecular mechanisms involved in brain function, and emphasizing the connections between the molecular changes and behavior. It is the untiring efforts of those magnesium researchers who have dedicated their lives to unraveling the mysteries of magnesiums role in biological systems that has inspired the collation of this volume of work.
This volume is a comprehensive source of information on the fundamentals of hearing and sound physics. Using research from 1980 onward, this book is a critical review of past and up-to-date research findings and concepts on the effects of noise on people; it focuses on the psychological and physiological affects of noise on hearing and performance. This text elucidates the interrelations of the acoustical, physiological, psychological, and sociological factors that are involved in making noise a problem to individuals and societies. Also discussed are hearing loss, speech communications, annoyance, and health effects criteria for the limitation of exposures to noise in living and work areas. Key Features * Physical characteristics of sound and noise * Acoustical-sensorineural response characteristics of the ear * Basic psychological sensations and perceptions that ensue from analysis of sound and noise by the auditory system * Laboratory and real-life research on the impairments to hearing, speech communication, task performance, and mental and bodily health that occur from exposure to noise * Physical measures which predict adverse effects on hearing, behavior, and health from exposure to noise
The surprising science of hearing and the remarkable technologies that can help us hear better Our sense of hearing makes it easy to connect with the world and the people around us. The human system for processing sound is a biological marvel, an intricate assembly of delicate membranes, bones, receptor cells, and neurons. Yet many people take their ears for granted, abusing them with loud restaurants, rock concerts, and Q-tips. And then, eventually, most of us start to go deaf. Millions of Americans suffer from hearing loss. Faced with the cost and stigma of hearing aids, the natural human tendency is to do nothing and hope for the best, usually while pretending that nothing is wrong. In Volume Control, David Owen argues this inaction comes with a huge social cost. He demystifies the science of hearing while encouraging readers to get the treatment they need for hearing loss and protect the hearing they still have. Hearing aids are rapidly improving and becoming more versatile. Inexpensive high-tech substitutes are increasingly available, making it possible for more of us to boost our weakening ears without bankrupting ourselves. Relatively soon, physicians may be able to reverse losses that have always been considered irreversible. Even the insistent buzz of tinnitus may soon yield to relatively simple treatments and techniques. With wit and clarity, Owen explores the incredible possibilities of technologically assisted hearing. And he proves that ears, whether they're working or not, are endlessly interesting.
The collection of systems represented in Sourcebook of genomic programs, although this work is certainly well Models for Biomedical Research is an effort to re?ect the represented and indexed. diversity and utility of models that are used in biomedicine. Some models have been omitted due to page limitations That utility is based on the consideration that observations and we have encouraged the authors to use tables and made in particular organisms will provide insight into the ? gures to make comparisons of models so that observations workings of other, more complex, systems. Even the cell not available in primary publications can become useful to cycle in the simple yeast cell has similarities to that in the reader. humans and regulation with similar proteins occurs. We thank Richard Lansing and the staff at Humana for Some models have the advantage that the reproductive, guidance through the publication process. mitotic, development or aging cycles are rapid compared As this book was entering production, we learned of the with those in humans; others are utilized because individual loss of Tom Lanigan, Sr. Tom was a leader and innovator proteins may be studied in an advantageous way and that in scienti?c publishing and a good friend and colleague to have human homologs. Other organisms are facile to grow all in the exploratory enterprise. We dedicate this book to in laboratory settings or lend themselves to convenient analy- his memory. We will miss him greatly.
