Risk exposure of dairy cows to environmental contamination of brick kilns on milk content of antioxidants and heavy metals in Al-Nahrawan region, Iraq

Long-term exposure to large quantities of toxic gases and heavy metals emitted by brick kilns can affect directly or indirectly on farm lactating animals, which influencing human health through consumption of their dairy products. Therefore, we investigated concentrations of heavy metals (HMs) including cadmium (Cd) and lead (Pb), as well as hydrogen sulfide (H2S), antioxidants, catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) in addition to malondialdehyde (MDA) in fresh milk. Totally, we selected 180 lactating cows; 140 reared / pastured near the active brick kilns as exposed group, and 40 cows existed at agricultural regions as control group during June-August 2021. The findings of exhibited a significant elevation in Cd, Pb, H2S and MDA, while decrease in CAT, GPx and SOD levels in exposed group. Among different age groups, there were variable significant values for the examined parameters. In the cases of  Cd, Pb and H2S levels, significant higher values were observed in a group of >8 year-olds in comparison with a group of < 4, while in the cases of CAT, GPx and SOD, significant drops were detected in the over 8-year-old cows than in the 4-8 and < 4.  Elevated values of MDA by age increasing were also observed. In conclusion, milk and its derivatives may likely exposed to HMs contamination. To date, available information is fragmentary; therefore, further studies of milky products are essential to monitor an existence of HMs regularly and to provide important information about their HM contents.