In an i n v e s t i g a t i o n o f the b e h a v i o r a l e f f e c t s o f Occupational Exposure t o lead, n i n e t e e n measures of neuromuscular performance and f i v e measures o f t h e body burden of l e a d were obtained from 316 experimental and 1 1 2 c o n t r o l s u b j e c t s . The experimental s u b j e c t s were v o l u n t e e r s from among worhers exposed t o i n o r g a n i c lead a t t h e i r jobs i n t h r e e s t o r a g e (lead-acid) b a t t e r y manufact u r i n g companies; t h e c o n t r o l s were v o l u n t e e r s from companies involved i n o t h e r various t y p e s o f l i g h t manufacturing. neuromuscular f u n c t i o n i n g and body burden of l e a d were determined through t h e use o f c o r r e l a t i o n and m u l t i p l e -r e g r e s s i o n analyses. analyses suggest t h a t f u n c t i o n a l c a p a c i t y decreased i n t e r m of tremor and eyehand coordination but increased i n terms of muscular s t r e n g t h . In a d d i t i o n , t h e d a t a suggest t h a t t h e s e changes occur on t h e p r e f e r r e d s i d e and a t blood-lead l e v e l s between 70 and 79 micrograms p e r cent, I n s t i t u t e f o r Occupational S a f e t y and Health, Department of Health, Education and Welfare, under Contract No. HSM 99-72-123, "Evaluation of Behavioral Functions i n Workers Exposed t o Lead," The authors wish t o acknowledge t h e i r s u b s t a n t i a l indebtedness t o t h e following persons who were involved i n various phases of t h i s research
Effects of acoustical stimulation on human equilibrium were measured on a rail test developed by Graybiel and Fregly [Acta Otolaryngol. 61, 292–312 (1966)]. Two tasks were used—standing with eyes open on rails 114in. and 34in. wide and standing with eyes closed on rails 134in. and 114in. wide. Five noise conditions were used—bilateral and unilateral presentations of impact (135 dB) and continuous (110 dB), and a bilateral control (75 dB). Analyses revealed no significant effects of types of noise on rail performance. These findings appear somewhat at variance with earlier results [H. C. Sommer and C.S. Harris, Aerospace Med. Res. Lab. Rep. 70-26, Wright-Patterson AFB, Ohio (1970); C.W. Nixon, C.S. Harris, and H. E. von Gierke, Aerospace Med. Res. Lab. Rep. TR-66-85, Wright-Patterson AFB, Ohio (1966)] indicating that asymmetrical, free-field noise stimulation produced significant impairment on a similar test, but their asymmetrical conditions involved unequal protection of the ears, resulting in a much greater interaural intensity difference.
A synthetic-work approach was employed in an investigation of the effects of 90-dB continuous and periodic 96-dB intermittent broad-band noise on human performance. Ten Navy and Air Force ROTC cadets worked the tasks of a multiple-task performance battery (MTPB) 12 h a week (in three, 4-h sessions) during a 4-week training period. Subsequently, they were required to work 4 days, 8 h per day on a split-shift schedule during the presence of noise, and finally, work 2 additional days on the same split-shift schedule under quiet conditions. Mean percentage of baseline performance (a composite index of performance) was enhanced by a periodic 96-dB intermittent noise, and the extent of the effect varied as a function of the number of tasks concurrently performed in the work situation. On the other hand, 90-dB continuous noise neither enhanced nor degraded performance. [Research supported by the U. S. Army Behavior and Systems Research Laboratory, Army THEMIS Contract; and by U. S. Army Medical Research and Development Command.]
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