Noise-induced hearing loss from exposure to tractors and other farm implements.

The relationship between noise-induced hearing loss (NIHL) and hypertension is well-accepted. The problem of noise associated with some leisure activities is known but the relationship between NIHL and leisure activity has been less extensively studied. Hypertension has been well documented. The linkage between NIHL has been made. These relationships have recently been documented. (1)

Compensation claims for hearing loss allegedly sustained while working can become confusing when claimants engage in noisy leisure activities. With the link between NIHL and hypertension becoming known, claims for hypertension due to exposure to occupational noise may also follow. Identifying NIHL or hypertension is the responsibility of a physician. Defending an organization from inappropriate claims is the responsibility of an attorney.

Occupational Safety and Health Administration regulations require that workers who are exposed to noise in excess of 85 decibels (dB) on a time-weighted basis for eight hours must be supplied with hearing protection devices while on the job. The responsibility to create and enforce a hearing conservation program rests with management.

Data for the scientific study on which the present installment is based was obtained from workers at several different plants, performing similar tasks for a single, large firm. The company has had an effective hearing conservation program in place for more than two decades. Workers have not been exposed to noise in excess of 85 dB while on the job. Compliance with the hearing conservation program is regularly monitored. Based on interviews with senior medical personnel, safety officers, and supervisors, it is felt that personal non-compliance while on the job is relatively uncommon. However, several sub-populations of employees with NIHL have been identified. The sources of noise to which these people were exposed involved participation in recreational activities. This article discusses the relationship between exposure to noise generated by tractors and other self-propelled farm implements and hearing loss. Connections with hypertension are secondary.

BACKGROUND

Noise-induced hearing loss is defined as the loss of auditory acuity secondary to exposure to noise. (2) Like presbycusis, noise-induced hearing loss is cumulative over time. However, the major loss in hearing is in the frequencies between 3,000 and 6,000 cycles per second or Hertz (Hz). (3) Using an audiogram, these frequencies are commonly assessed by presenting a tone of 4,000 Hz.

There is a noticeable "rebound" at 8,000 Hz in younger persons exposed to noise. (4) In this way, noise-induced hearing loss may be distinguished from presbycusis. Additional diagnostic criteria are usually incorporated before making a definitive diagnosis of noise-induced hearing loss. (5) These are summarized in Exhibit 1.

 
Exhibit 1. Diagnostic Criteria for Noise-Induced 
Hearing Loss (6) 
 
1. Loss must be sensorineural with damage primarily in 
   the cochlear hair cells. 
 
2. History of long-term exposure to intense noise levels. 
 
3. Hearing loss must develop slowly over a period of 
   years and in the first 8-10 years of exposure. 
 
4. Loss must start in 3,000 to 6,000 Hz frequencies and 
   be bilaterally symmetric. 
 
5. Speech discrimination scores are relatively unaffected. 
 
6. Hearing loss stabilizes upon removal from noisy 
   environment. …