Electrophysiological evidence for impairment of contrast sensitivity in mercury vapor occupational intoxication.
Contrast sensitivity (CS) was evaluated in 41 former workers from a lamp manufacturing plant who were on disability retirement due to exposure to mercury and 14 age-matched controls. The CS was measured monocularly using the sweep visual evoked potential (sVEP) paradigm at 6 spatial frequencies (0.2, 0.8, 2.0, 4.0, 15.0, and 30 cpd). Statistical difference (p<0.05) was found between the controls and the patient right and left eyes for 2.0 and 4.0 cpd. According the results in those spatial frequencies the eyes were classified in best and worst. Statistical differences were found between the controls and the best eyes for 2.0 and 4.0 cpd and for 0.8, 2.0, and 4.0 cpd for their worst eyes. No correlation was found between CS results and the time of exposure (mean=8.9 yr+/-4.1), time away from the mercury source (mean=6.0 yr+/-3.9), urinary mercury level at the time of work (mean=40.6 microg/g+/-36.3) or with the mercury level at the CS measurement time (mean=1.6 microg/g+/-1.1). We show the first evidence of a permanent impairment in CS measured objectively with the sVEP. Our data complement the previous psychophysical works reporting a diffuse impairment in the CS function showing a CS reduction in the low to middle spatial frequencies. In conclusion, non-reversible CS impairment was found in occupational exposure to mercury vapor. We suggest that CS measurement should be included in studies of the mercury effects of occupational exposure.
Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Prof. Mello Moraes, 1721 Bloco A sala D-9, São Paulo 05508-900, SP, Brazil. costamf@usp.br
Marcelo Fernandes
MF
Costa
Sandra
S
Tomaz
John Manuel
JM
de Souza
Luiz Carlos de Lima
LC
Silveira
Dora Fix
DF
Ventura
D000328:Adult; D000395:Air Pollutants, Occupational / Q000633:toxicity*; D016022:Case-Control Studies; D015350:Contrast Sensitivity / Q000187:drug effects*; D004594:Electrophysiology; D005074:Evoked Potentials, Visual / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008628:Mercury / Q000633:toxicity*; D008630:Mercury Poisoning / Q000175:diagnosis*; D008875:Middle Aged; D016273:Occupational Exposure
D000395:Air Pollutants, Occupational; D008628:Mercury