Abstract
Formalin treatments are frequently used to control water molds during hatchery incubation of salmonid eggs, creating potential occupational safety and health issues. This investigation evaluated the use of a novel technique to enclose the air gap from formalin treatment tubes to 16-tray vertical-flow incubation stacks. Standard formalin treatments of 1667 mg/L for 15-minutes were administered to one, three, or five stacks, both with, and without air gap enclosures. Enclosing the air gap did not significantly reduce aerosolized formaldehyde levels. Even during the treatment of five incubation stacks when formalin amounts were the greatest, mean (SE) peak airborne formaldehyde levels were 1.6 (0.2) mg/L and 1.5 (0.2) mg/L, either with or without air gap enclosure, respectively. The failure of air gap enclosure indicates other techniques are required to decrease aerosolized formaldehyde during formalin treatments of fish eggs in vertical-flow incubators.
Highlights
Formalin is one of the most widely used therapeutic agents in fish culture [1], and consists of 37% formaldehyde and methanol in an aqueous solution
Voorhees and Barnes [11] found that the treatment of five vertical-flow incubation stacks produced airborne formaldehyde levels that exceeded permissible exposure level (PEL) of 2.0 ppm set by the Occupational Safety and Health Administration (OSHA)
The use of the air-gap eliminator had no significant effect on any of the parameters measured (Table 2). The time it took to reach peak formaldehyde levels, the peak of formaldehyde reached, the time to reach PEL, the time the level stayed above PEL, and the time to get back to the base level were similar between the groups
Summary
Formalin is one of the most widely used therapeutic agents in fish culture [1], and consists of 37% formaldehyde and methanol in an aqueous solution. In the United States, formalin is approved for the control of external parasites on finfish or shrimp and for fungal control on finfish eggs [8]. Formalin is routinely used to control fungal (water mold) infections during the incubation of salmonid eggs [9], when using vertical-flow incubators [10]. Such use can be potentially problematic for aquaculture workers. Voorhees and Barnes [11] found that the treatment of five vertical-flow incubation stacks produced airborne formaldehyde levels that exceeded permissible exposure level (PEL) of 2.0 ppm set by the Occupational Safety and Health Administration (OSHA). To prevent back-flow siphon of water into the tubing, an air gap is required between the end of the tubing and the water in the incubation stack
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