Purpose: In the present study, we aimed to identify the effect of three increasing doses of most widely preservative, formaldehyde (FA) on the urinary system using human embryonic kidney cells (HEK-293) in vitro. Materials and methods: The HEK-293 cells were grown in Dulbecco’s Modified Eagle medium (DMEM, Gibco, USA) supplemented with 10% of fetal bovine serum, 100 IU/ml penicillin and 100 μg/ml of streptomycin (Gibco, USA) using 25cm2 flasks (Nunc, Denmark), in a CO2 incubator (Heal Force) at 37°C are treated with 19 % formaldehyde in DMEM supplemented with 10% of fetal bovine serum to yield final concentrations of 0.05 μl/ml, 0.1 μl/ml, 0.5 μl/ml and 1.0 μl/mlof 19% FA. Results: The result showed that statistically significant dose dependent decrease in cell viability of HEK-293 cells with exposure to increasing concentration of FA (0.05 μl/ml, 0.1 μl/ml, 0.5 μl/ml and 1.0 μl/ml) on MTT assay. Extremely huge dose dependent DNA damage with a dose dependent up regulation of mRNA expression of pro-apoptotic iNOS and TNF- gene was observed when HEK-293 cells are treated with the increasing concentration of FA. In addition, the protein expression levels of Bcl-2 and Bax revealed that increasing concentration of FA on HEK-293 cells down regulated the anti-apoptotic Bcl-2 and up regulated pro-apoptotic Bax gene. Conclusions: Our result indicates that, high dose of FA is more dangerous than the low dose on HEK-293 cells with cellular damage.