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.
Formalin is one of the most widely used therapeutic agents in fish culture [
Formalin is routinely used to control fungal (water mold) infections during the incubation of salmonid eggs [
By providing an interface between formalin and the atmosphere, the air gap was hypothesized to contribute to formaldehyde aerosolization. Because no equipment currently exists to eliminate this air gap, a novel device was developed and described in this article. Additionally, its potential effects on airborne formaldehyde levels were evaluated.
The study was conducted at Cleghorn Springs State Fish Hatchery, Rapid City, SD, USA, using 11˚C spring water (total hardness as CaCO3, 36 mg/L; alkalinity as CaCO3, 210 mg/L; pH, 7.6; total dissolved solids, 390 mg/L). Formalin (Parasite-S; 37% formaldehyde, 6% - 14% methanol; Syndel USA, Ferndale, Washington) was administered to vertical-flow incubators (MariSource, Fife, Washington) using a peristaltic pump (Masterflex model 07524-40 pump driver; 07519-25 pump head; cartridge model 07519-85; Cole-Parmer Instrument Company, Vernon Hills, Illinois). Each incubation stack of 16 trays received 11.34 L/min of constant water flow. Formalin treatments were set at 1667 mg/L for 15 minutes [
In order to prevent the back siphon of water from the incubation stack into the formalin reservoir, the formalin was not injected directly into the water. Rather, there was a gap between the end of the tubing (2.4 mm i.d.; C-Flex; Cole-Parmer Instrument Company, Vernon Hills, Illinois) coming from the peristaltic pump and the uppermost incubation tray (
The incubation room contained five sixteen-tray stacks and five eight-tray stacks (
Airborne formalin concentrations were measured using a formaldehyde meter (model HAL-HFX205l; HalTech; Fontana, California). Prior to any trials, basal formalin concentrations were measured and consistently found to be 0.2 mg/L. During the trials, formalin measurements were recorded every min for the first 60 min after the start of a treatment. If the concentration was at the basal concentration after the first 60 min, no further formalin readings were conducted. However, if the values were elevated above the basal level, additional readings were taken thereafter at 30 min intervals until basal readings were obtained.
Formaldehyde concentrations were compared to the United States Department of Labor, Occupational Safety and Health Administration (OSHA) regulation limits of 0.75 mg/L permissible exposure limit (PEL) measured as an 8-hour
Trial | Number of Stacks | Use of Test Tube |
---|---|---|
1 | 1 | yes |
2 | 1 | no |
3 | 3 | yes |
4 | 3 | no |
5 | 5 | yes |
6 | 5 | no |
time-weighted average (TWA), and the 2.0 mg/L short-term exposure limit (STEL) as measured in a 15-minute period, and the OSHA action level of 5.0 mg/L TWA [
Data were analyzed using the SPSS (9.0) statistical analysis program (SPSS, Chicago, Illinois). Statistical significance was predetermined at p < 0.05. Two-way ANOVA was used for analysis.
The use of the air-gap eliminator had no significant effect on any of the parameters measured (
Obviously, eliminating the formalin treatment tubing air gap had no effect on
Number of Stacks | Measurement | Use of Test Tube | |
---|---|---|---|
Yes | No | ||
1 | Time to peak formaldehyde levels (min) | 28.5 ± 4.2 | 22.5 ± 2.5 |
Peak formaldehyde levels (mg/L) | 0.4 ± 0.0 | 0.5 ± 0.0 | |
Time to reach above PEL1 | 0.0 ± 0.0 | 0.0 ± 0.0 | |
Time above PEL | 0.0 ± 0.0 | 0.0 ± 0.0 | |
Time back to base | 52.0 ± 3.3 | 49.3 ± 3.2 | |
3 | Time to peak formaldehyde levels | 25.0 ± 2.7 | 25.3 ± 2.3 |
Peak formaldehyde levels | 1.2 ± 0.1 | 1.0 ± 0.1 | |
Time to reach above PEL | 16.2 ± 1.9 | 12.5 ± 4.2 | |
Time above PEL | 19.2 ± 2.2 | 12.3 ± 4.1 | |
Time back to base | 62.0 ± 3.4 | 62.5 ± 0.8 | |
5 | Time to peak formaldehyde levels | 24.5 ± 2.8 | 25.7 ± 2.2 |
Peak formaldehyde levels | 1.6 ± 0.2 | 1.5 ± 0.2 | |
Time to reach above PEL | 14.0 ± 1.4 | 14.0 ± 2.4 | |
Time above PEL | 27.2 ± 2.7 | 24.2 ± 3.8 | |
Time back to base | 77.3 ± 14.1 | 84.7 ± 5.1 |
1Permissible Exposure Level = PEL.
aerosolized formaldehyde levels in this study. These results indicate that most of the formaldehyde aerosolization is likely occurring due to surface deposition as the water falls from each incubation tray into the tray immediately below it [
The back-flow of water from the incubation stack into the barrel of formalin used for egg treatment was unexpected and also very problematic. It is possible that if such back-feeding occurred during actual production-level formalin treatments, that it might not be detected, resulting in a dilution of the source formalin. Treatment at lower formalin concentrations may be ineffective at egg fungal control [
The novel air-gap elimination device described in this study was ineffective at reducing airborne formaldehyde levels. Thus, further experimentation is needed to find ways to reduce the occupational exposure of aquaculture workers to formaldehyde during routine egg treatments. Although potentially disconcerting, the publication of negative results is also encouraged to prevent study duplication and promote learning [
We thank Cody Treft and Tabor Martin for their assistance with this study.
The authors declare no conflicts of interest regarding the publication of this paper.
Voorhees, J.M., Fletcher, B. and Barnes, M.E. (2018) Enclosing the Air Gap from Formalin Delivery Tubing to Vertical-Flow Fish Egg Incubators Does Not Decrease Aerosolized Formaldehyde Levels. Open Journal of Safety Science and Technology, 8, 98-105. https://doi.org/10.4236/ojsst.2018.83006