On December 6, 1999, NIOSH received a confidential health hazard evaluation request regarding possible health effects in workers exposed to Solcenic HL hydraulic fluid at the Robinson Run Mine in Shinnston, West Virginia. Solcenic HL emulsion is used in the closed loop hydraulic system that pressurizes the piston-driven roof supports in the longwall section of the underground coal mine. Solcenic HL is a proprietary formulation of mineral oil, alcohol, poly glycol, inorganic salt, organic acid salt, and a triazine biocide. It is similar in formulation to emulsifiable metal working fluids which have been associated with respiratory disorders, work related asthma, and allergic and irritant skin disorders (NIOSH, 1998a). We conducted telephone and on-site interviews with miners who were concerned that exposures to Solcenic HL emulsion might be putting them at risk for sinusitis, rhinitis, adult onset occupational asthma, and dermatitis, especially during periods of atypical exposure such as when working around large spills. We administered a medical-work history questionnaire on October 18, 19, and 20, 2000. Its purpose was to assess the prevalence of various respiratory and skin disorders and symptoms in relation to possible sources and pathways of exposure, especially to Solcenic HL emulsion. The questionnaire requested demographic data, a brief work history, possible workplace exposures, and included questions designed to identify individuals with sinusitis (nasal), breathing, and dermal (skin) disorders. Because Solcenic HL emulsion is only used at the longwall, miners were grouped as either "longwall miners" (potentially exposed individuals) or "nonlongwall miners" (minimally exposed or nonexposed individuals). The minimally exposed group includes some miners who occasionally assisted with relocation and maintenance of the longwall equipment. There were 85 respondents out of 250 current employees representing 100 percent (33/33) of the longwall workforce and about 25 percent (52/250) of the "nonlongwall workforce." The prevalence of self-reported sinus or nasal symptoms that required medical attention was 24 percent (8/33) among longwall miners versus 48 percent (24/52) among miners whose primary work areas were other areas of the mine. Because the rate of symptoms was higher in the nonexposed group, there does not appear to be a positive relationship between the routine use of Solcenic HL emulsion and nasal/sinus symptoms. However, self-reporting bias is a possible explanation for the higher rate of symptoms in the nonexposed group; those without symptoms may not have been motivated to respond to the questionnaire. Exposure misclassification is another possible explanation; some of the "minimally exposed workers" may have experienced acute exposures to Solcenic HL emulsion during their temporary assignments to work on the longwall. The prevalence of self-reported adult onset asthma was 6 percent (2/33) among longwall miners and 6 percent (3/52) among nonlongwall miners [For comparison, McWhorter et al. (1989) estimated the prevalence of active asthma among U.S. adults to be 2.6 percent.] Of the five self-reported cases, two worked on the longwall, two worked throughout the mine including the longwall, and one worked on a continuous mining section. Four of the five, including the continuous mining section worker, reported that "Solcenic" or "hydraulic fluid" exacerbated their asthma symptoms. Self-reporting bias and misclassification are concerns, and we can neither establish nor rule out a relationship between exposure to Solcenic HL emulsion and self-reported adult onset asthma. The prevalence of self-reported dermal symptoms that required medical treatment was 21 percent (7/33) for longwall miners and 25 percent (13/52) for other miners. Once again, self-reporting bias and misclassification are concerns, and we can neither establish nor rule out a relationship between exposure to Solcenic HL emulsion and self-reported mine-related dermatitis. Concurrent with obtaining and evaluating the medical-work history information, we collected and analyzed samples of the bulk Solcenic HL, the Solcenic HL emulsion, emulsion leakage from the mine floor, and area samples of the mine air to characterize the work environment. We identified two agents that warranted further investigation. The first agent was formaldehyde (a breakdown product of the triazine biocide in Solcenic HL), which is associated with upper respiratory and dermal irritation and sensitization and is considered by NIOSH to be a potential occupational carcinogen. The second agent was microbials (i.e., bacteria and fungi) from the shearer sprays and the mine air, which are also associated with upper respiratory symptoms, adult onset asthma, and dermal symptoms. The maximum concentration of formaldehyde in air during our sampling program was 0.027 parts per million (ppm). This is two orders of magnitude below the MSHA Permissible Exposure Limit (PEL) of 2 ppm, one order of magnitude below the American Conference of Governmental Industrial Hygienists (ACGIH) 2000 Threshold Limit Value (TLV) of 0.3 ppm, and similar in magnitude to the NIOSH Recommended Exposure Limit (REL) of 0.016 ppm. Although the PEL is the legally enforceable limit, employers are encouraged to follow the most protective criterion among the PEL, TLV and REL. The NIOSH REL for formaldehyde is a qualitative value based primarily on the analytical limit of detection. There were no large spills of Solcenic HL emulsion during our sampling program, but we believe that formaldehyde concentrations in air during atypical events have the potential to exceed the MSHA PEL. We evaluated the possibility that triazine from spillage of Solcenic HL emulsion might adsorb onto or absorb into rockdust and be converted to formaldehyde after inhalation and deposition of the dust in the respiratory tract. The amount of triazine that might be adsorbed onto or absorbed into rockdust that becomes aerosolized and inhaled was found to be negligible. In our microbial evaluation, we sampled the Solcenic HL emulsion from the hydraulic lines and found no bacteria and four colony forming units per milliliter (CFU/ml) of basidiomycetes and 2 CFU/ml of an unidentified fungus. These low levels of fungi in the emulsion could have originated from contact with equipment surfaces during sampling. We also sampled the shearer spray water for microbial content and found several species of bacteria that may be pathogenic or that are indicators of pathogenic potential. The shearer spray is fed by surface water that passes through a coarse sand filter before being sprayed to suppress dust from the shearer. Based on good public health practice, we recommend additional filtration or treatment for the shearer sprays. We sampled the air on June 13-14, 2000, for fungi and bacteria. Fungi concentrations in the mine ranged to 9.6 x 103 CFU per cubic meter of air (CFU/m3) and bacteria concentrations ranged from below the level of detection to 1.4 x 105 CFU/m3. The predominant fungal genera outside the mine was Cladosporium and the predominant fungal genus inside the mine were Cladosporium, Penicillia, and basidiospores. The bacteria found in the mine air included Actinomycetes, Rhodococcus, Actinobacter, and Pseudomonas. Although these are ubiquitous environmental microbials, exposures to fungi and bacteria have been associated with sinus/nasal and asthmatic symptoms in susceptible individuals. In conclusion, the hypothesis that miner exposures to Solcenic HL emulsion caused or exacerbated the reported health effects in some workers can neither be established nor ruled out. Exposure to formaldehyde is possible during atypical events such as large spills. Pathogenic microbial species were also found in both the shearer spray and the mine air, but their relationship to the reported symptoms is unknown. The following recommendations are based on information derived from studies of metal working fluid exposed workers. Based on best work practices, it would be prudent to: 1. Follow appropriate health and safety guidelines in the NIOSH Metalworking Fluids Criteria Document. 2. Evaluate substitutes to Solcenic HL or components of Solcenic HL that may be used at dilutions that minimize the risk of nasal/sinus, respiratory, and dermal symptoms. 3. Implement a preventive maintenance program for the longwall hydraulic system, with the goal of minimizing leakage and spillage of the Solcenic HL emulsion. Monitor the volumetric rate of consumption of Solcenic HL to identify system failures and to trigger preventive actions. Include routine recovery of the hydraulic fluid during longwall moves, rather than allowing it to spill out into the work area. 4. Ensure that the manufacturer’s instructions are followed to maintain the concentrations of the triazine biocide above levels necessary to prevent microbial growth in the emulsion, yet below the level that could cause miners to experience dermal effects and/or respiratory irritation. 5. Implement a program to avoid skin contact with Solcenic HL emulsion. 6. Provide an occupational medical monitoring program for all miners who routinely have skin contact with Solcenic HL concentrate or emulsion or who experience symptoms suggestive of sensitization. Consider implementing a program similar to that outlined in the NIOSH Metalworking Fluids Criteria Document. 7. Provide all miners with appropriate education and training, particularly with respect to self-referral for medical evaluation if they develop symptoms suggestive of asthma, hypersensitivity pneumonitis, other respiratory conditions, or dermatitis. 8. Sample for formaldehyde during atypical events such as large spills. 9. Provide additional filtration or microbial treatment for the feed water supply to the shearer sprays. NIOSH did not find a health hazard to exist during routine operations. However, nasal/sinus, upper respiratory, and dermal symptoms have been associated in the literature with exposure to components of the emulsion used in the mine and to the bacteria/fungi that were found in the shearer sprays and in the mine air. Air sampling indicates that the MSHA PEL for formaldehyde is unlikely to be exceeded during routine operations, although concentrations at or above the NIOSH REL are possible. Therefore, formaldehyde exposure should be measured during atypical events, such as large spills. To minimize symptoms among susceptible workers and to maintain formaldehyde concentrations below the NIOSH REL, recommendations are made to minimize exposures.