Table 4.
Summary of approaches used in the risk assessment strategies for formaldehyde (FA)
| Effect | Supporting a NOAEL approach | Supporting a linear extrapolation |
|---|---|---|
| Repair of DNA–protein crosslinks | No accumulation of DPX based on rapid in vivo repair in rats | Accumulation of DPX based on in vitro immortalized cell linesa |
| DPX formation in lymphocyte cultures | DPX formation was non-linear and the DPX level in non-exposed cells was similar to DPX in cells at low FA levels | – |
| Genotoxic effects in nasal and buccal mucosa cells | Chromosomal aberrations and MN are considered to be sensitive genetic endpoints. Both are suggested to show NOAEL at indoor air levels | A NOAEL is not accepted for FA induced genotoxic effects |
| Genotoxic effects in peripheral lymphocytes | In vitro cytogenetic tests suggested NOAEL | NOAEL is not accepted for FA induced genotoxic effects |
| Development of nasal tumors | In rats, the exposure–effect relationship was non-linear with an apparent NOAEL | A linear exposure–response relationship at low exposures cannot be disproved statistically |
| Development of nasal tumors | In rats, cell proliferation was considered crucial for development of tumors | Assuming that tumor development may occur without cytotoxicity induced increase in cell proliferation |
| Development of nasal tumors | In rats, a minimum FA exposure level was necessary even in the case of cell proliferation | Assuming that all FA exposure levels increase the risk of development of tumors |
| Nasopharyngeal cancer in humans | The FA-induced effects seem to occur at high exposure levels, especially high peak levels. An apparent level exists where no increased risk was observed | Due to a limited number of cases, a low-level exposure risk cannot be disproved |
| Lymphohematopoietic malignancies in humans | Although limited consistency exists across studies, potential effects seem to occur at high exposure levels, especially high peak levels. An apparent level exists where no increased risk was observed | Due to a limited number of cases, a low-level exposure risk cannot be disproved |
For explanations see text
aSubramaniam et al. (2007)