Vibroacoustic disease: some forensic aspects

Vibroacoustic disease (VAD) is an insidious environmental entity caused by occupational exposure to large pressure amplitude and low frequency (LPALF) noise (> or = 90 dB SPL, < or = 500 Hz). Significant disabilities may result, and issues of worker's compensation should be openly discussed and settled. Toward this goal, a rigorous review of all available information on this disease was undertaken in order to document the need to define industrial exposure standards, and to settle on the diagnostic procedures that will help distinguish the VAD from other, similar conditions.

We reviewed the medical files of 236 male Caucasians employed as aircraft technicians who had been diagnosed with VAD and monitored for at least 15 yr. The natural history of the disorder was studied in detail, emphasizing the clinical diagnostic criteria and the outcome of disabilities.

Among the 236 cases, 172 (73%) were disabled after an average of 24 yr (SD = 6.9) of occupational exposure. The primary categories of disabilities were neurological (81, 34%), malignant (28, 11.9%), psychiatric (23, 9.7%), cardiovascular (16, 6.8%), and osteoarticular (14, 5.9%). After the onset of industrial exposure to LPALF noise, the minimum time for these disabilities to manifest themselves was 16 yr. The most serious complication was multiple attempted suicide. Such attempts were fortunately rare (5, 2.1%) and successful only once. Echocardiograms showed characteristic changes in pericardial structures, involving proliferation of the extracellular matrix, lack of cilia and five pericardial layers instead of three. This has been studied in pericardial biopsy material obtained during coronary bypass surgery for coronary insufficiency (six cases), and by autopsy (four cases).

These findings appear to be pathognomonic for the VAD, and the echocardiogram has been confirmed as a fundamental diagnostic tool. The degree of disability due to VAD can be determined from Portuguese national disability tables, which cover almost all of the VAD-induced disabilities. However, these tables do not specify LPALF noise as an occupational hazard, rendering them inapplicable to VAD patients. Also, suicide, a most serious psychiatric consequence, is not covered by these tables. Such situations highlight the absolute necessity to recognize LPALF noise as the cause of VAD, and as an industrial hazard.