Occupational exposure to airborne mercury during gold mining operations near El Callao, Venezuela

• Published in: International archives of occupational and environmental health 2001-04, Vol.74 (3), p.206-212
• Main Authors: DRAKE, Pamela L, ROJAS, Maritza, REH, Christopher M, MUELLER, Charles A, JENKINS, F. Michael
• Format: Article
• Language: English
• Subjects: Acetylglucosaminidase - urine; Air Pollutants, Occupational - adverse effects; Air Pollutants, Occupational - analysis; Air Pollutants, Occupational - urine; Analysis of Variance; Biological and medical sciences; Chemical and industrial products toxicology. Toxic occupational diseases; Creatinine - urine; Cross-Sectional Studies; Environmental Monitoring; Epidemiological Monitoring; Gold; Humans; Medical sciences; Mercury - adverse effects; Mercury - analysis; Mercury - urine; Metals and various inorganic compounds; Mining; Occupational Exposure; Statistics, Nonparametric; Toxicology; Venezuela; Venezuela - epidemiology; Venezuela, El Callao
• ISSN: 0340-0131; 1432-1246
• DOI: 10.1007/s004200000206

The National Institute for Occupational Safety and Health (NIOSH) recently conducted a cross-sectional study during gold mining operations near El Callao, Venezuela. The purpose of the study was to assess mercury exposures and mercury-related microdamage to the kidneys. The study consisted of concurrent occupational hygiene and biological monitoring, and an examination of the processing techniques employed at the different mining facilities. Mercury was used in these facilities to remove gold by forming a mercury-gold amalgam. The gold was purified either by heating the amalgam in the open with a propane torch or by using a small retort. Thirty-eight workers participated in this study. Some participants were employed by a large mining company, while others were considered "informal miners" (self-employed). Mercury exposure was monitored by sampling air from the workers' breathing zones. These full-shift air samples were used to calculate time-weighted average (TWA) mercury exposure concentrations. A questionnaire was administered and a spot urine sample was collected. Each urine sample was analyzed for mercury, creatinine, and N-acetyl-beta-D-glucosaminidase (NAG). The range for the 8-h TWA airborne mercury exposure concentrations was 0.1 to 6,315 micrograms/m3, with a mean of 183 micrograms/m3. Twenty percent of the TWA airborne mercury exposure measurements were above the NIOSH recommended exposure limit (REL) of 50 micrograms/m3, and 26% exceeded the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) of 25 micrograms/m3. The mean urine mercury concentration was 101 micrograms/g creatinine (microgram/g-Cr), and the data ranged from 2.5 to 912 micrograms/g-Cr. Forty-two percent of the study participants had urine mercury concentrations that exceeded the ACGIH biological exposure index (BEI) of 35 micrograms/g-Cr. Urinary NAG excretion is considered a biological marker of preclinical, nonspecific microdamage to the kidney's proximal tubule cells. The mean urine NAG concentration was 3.6 International Units/g-Cr (IU/g-Cr) with a range of 0.5 to 11.5 IU/g-Cr. Three workers had urine NAG levels in excess of the reference values. Correlation analyses found statistically significant correlations between airborne mercury exposure and urine mercury level (P = 0.01), and between urine mercury level and urine NAG excretion (P = 0.01). In addition, the airborne mercury exposure data and urine mercury data were segregated by