What is caused by the increased nitrate levels?

Methemoglobinemia, or blue-baby syndrome, is a condition caused by the inability of the blood to deliver enough oxygen to the body. It is the most well-known effect of exposure to elevated levels of nitrate in drinking water. When nitrate is ingested it is converted to another chemical form, nitrite.

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;