Explanation:

• Excess nitrate in drinking water reacts with hemoglobin to form methemoglobin and impairs oxygen transport. This condition is called Methaeglobinemia or Blue Baby Syndrome.
• Mercury compounds in waste water are converted into extremely toxic methyl mercury by bacterial action. This may lead to Minamata disease.
• Long term ingestion of high fluoride in drinking water causes neuro-muscular disorders, gastrointestinal problems teeth deformity, hardening of bones and painful joints (skeletal Fluorosis)
• Silicosis is a lung disease caused by breathing in (inhaling) silica dust. Silica dust forms during mining, quarrying, tunneling, and working with certain metal ores. Silica is a main part of sand, so glass workers and sandblasters are also exposed to silica.