Worker Health Study Summaries
Research on long-term exposure
Embalming Students (Formaldehyde Exposure)
NIOSH studied formaldehyde exposure in embalming students from a college of mortuary science.
The National Institute for Occupational Safety and Health (NIOSH) does research on the health of workers and how they are affected by workplace exposure. In 1989, NIOSH studied students who were taking an embalming course.
The biological assays measured effects on chromosomes (micronuclei and sister-chromatid exchange) and on an enzyme, O6-Alkylguanine DNA Alkytransferase (ACT) that repairs DNA, (deoxyribonucleic acid), the genetic material of which the chromosomes are made. These tests measure subtle biologic effects that may have resulted from exposure to formaldehyde or embalming fluid. No health effects have been connected with any of these test results.
Why We Did the Studies
We wanted to know if exposures to low levels of formaldehyde, as occurs during embalming, caused changes in the cells in the mouth, nose, and blood. Micronuclei are fragments or small pieces of chromosomes. Everyone has some micronuclei. We wanted to know if exposure to formaldehyde during embalming increased the percentage of buccal (mouth) and nasal epithelial cells and blood lymphocytes containing micronuclei.
Sister chromatid exchanges (SCE) occur when pieces of DNA are exchanged from one chromosome to its homologous pair during cell division. Chromosomes are the structures in cells that contain genetic information. All persons have some SCEs. Since exposure to some toxic materials increased SCE, we wanted to know if the number of sister chromatid exchanges per cell were increased by exposure to formaldehyde.
We also wanted to know whether the activity of AGT that repairs DNA was decreased by low levels of exposure to formaldehyde, seen in embalming students. Formaldehyde can decrease the activity of AGT. This enzyme repairs DNA that has been damaged. It only repairs one of many specific types of DNA damage. Specifically, guanine, one of the bases in the DNA, may have alkyl groups added at the 0-6 position from a toxic agent in the environment. If the alkyl groups are not removed, the DNA can be misread when it is copied and a mutation will occur. When there is a lower level of AGT, the DNA may not be repaired as efficiently.
How we did the Study
Three weeks before the embalming class started, we collected blood and cells from the nose and mouth of students. We also collected the same samples 9 weeks after the class started. We separated the lymphocytes from other cells in the blood. We counted 1,500 epithelial cells from the mouth and nose and 2,000 lymphocytes from the blood. We determined the percent of each type of cell that contained micronuclei.
We determined the number of sister chromosome exchanges (SCE) per lymphocyte both before and after 9 weeks in the embalming class. We measured the ACT activity in the blood lymphocytes from both samples. We also measured exposure to formaldehyde during the embalming that was performed at the mortuary school and estimated the formaldehyde exposure at other embalmings that were performed.
The following are individual assays. The average for all subjects ± the standard deviation are given in parenthesis.
|Biological Assay||Prior to Embalming Course||Nine weeks into the Embalming Course|
|Number of SCE per cell 1||
|Number of cells with micronuclei per 1000 WBC cells counted 2||
|Number of cells with micronuclei per 1000 mouth cells counted2||
|Number of cells with micronuclei per 1000 nose cells counted 2||
|Amount of AGT, an DNA repair enzymes 3||
1Sister chromatid exchanges occur when a piece of DNA is exchanged from one chromosome to its homologous pair during cell division. Chromosomes contain genetic information.
2Chromosomal micronuclei are pieces or fragments of chromosomes. These occur when cells divide. All persons have some chromosomal micronuclei. There are no known health effects associated with this change.
3AGT, a DNA repair enzyme, repairs defects in DNA (see text for more details). Study of this enzyme are experimental. It is not known whether there are any health effects associated with changes in these enzymes.
The levels of micronuclei, SCEs, or AGT are not known to be associated with any health effects. Many factors in addition to formaldehyde exposure, may affect these levels, including cigarette smoking and some medications. Although these results are not predictive of the health as an individual, we wanted to know if formaldehyde exposure changes these levels among mortuary students as a group and whether these changes were associated with the amount of formaldehyde exposure.
We compared the percent of cells containing micronuclei before the course with the percent seen after 9 weeks. We concluded that taking an embalming course increased the number of micronuclei in mouth epithelial cells and in the blood lymphocytes (presumably because of exposure to formaldehyde). Though these increases were statistically significant, we saw only a very few micronuclei in the mouth cells. There was also a slight increase in the number of micronuclei in the cells from the nose, but the increase was not significant.
We wanted to know how much time between exposure to formaldehyde and the sampling of mouth cells was the best to use for predicting the percent of cells with micronuclei. We found that formaldehyde exposures 7 to 16 days before sampling were slightly more accurate than the exposure cumulated over the total 85 days, in predicting the percent of cells containing micronuclei.
We compared the number SCE per cell before the embalming class to the number seen 9 weeks after the class started. Since some toxic material increase the number of SCE per cells, we thought that we might find an increase in SCEs during the study period, but we found a significant decrease in the number of SCE during the study period. This decrease was mainly seen in woman. No genetic information is either gained or lost in a sister chromatid exchange. No one knows if there are any health effects associated with SCE.
In seven of the eight students who had no exposure to embalming fluid in the 3 months prior to the course, the levels of AGT decreased during the study period. This decrease was statistically significant. In 15 students who had exposure in the 3 months prior to the course, AGT activity decreased during the study period in 10 students and increased in 5 students. This result was not significant. However, there was no relationship between total formaldehyde exposure and decrease in AGT. A possible reason for this was that many students who performed embalming prior to the study had higher exposures to formaldehyde both before and during the study period so their AGT levels were already lowered. The changes in AGT levels may have been due to formaldehyde exposure, but the study did not prove this.
There are no health effects known to be related to these biologic effects. However, formaldehyde exposure at high concentrations causes cancer in animals and there is some evidence that it may cause cancer in humans. Therefore, if you still work with embalming fluid, it is wise to follow the Occupational Safety and Health Administration (OSHA) formaldehyde standard and use protective equipment and exhaust ventilation to reduce your formaldehyde exposure.
For more information please call the NIOSH toll-free number at 800-356-4674.
Hayes RB, Klein S, Suruda A, Schulte P, BoenigerM. Stewart P, Livingston GK, Oesch F: O-6-Alkylguanine DMA alkyltransferase activity in student embalmers. Am. J. Ind. Med. 31:361-365, 1997.
Levine AJ, Salvan A, Talaska G, Boeniger M. Suruda A, Schulte P: The Utility of Epithelial-cell Micronuclei in the Assessment of Intermittent Exposures. Biomarkers 2:135-138, 1997.
Titenko-Holland N, Levine AJ, Smith MT, Quintana PJE, Boeniger M. Hayes R, Suruda A, Schulte P: Quantification of Epithelial Cell Micronuclei by Fluorescence In Situ Hybridization (FISH) in Mortuary Science Students Exposed to Formaldehyde. Mut. Res.: Genetic Toxicology 371:237-248, 1996.
Suruda A, Schulte P, BoenigerM. Hayes R, Livingston G, Steenland K, Stewart P, Herrick R, Douthitt D and Fingerhut M: Cytogenetic Effects of Formaldehyde Exposure in Students of Mortuary Science. Cancer Epidemiology, Biomarkers & Prevention 2:453-460, 1993.(Study Report)