**5. Mercury in sewage effluents**

Municipal sewage has been noted as a significant environmental mercury (Hg) source. Mercury in the effluents of waste water treatment plants and mercury-based fungicides increase the discharge of mercury to the aquatic environment [34, 35]. Consumption of Hg-containing foods [12, 36] and exposure to common items like batteries [29] would increase the risks of mercury being excreted and flushed away in the city's sewage system. The mercury released by hospitals, dentist clinics, and other service facilities is a major source of Hg in sewage [37]. A total of 30 tons of total Hg (organic and inorganic) was loaded into sludge in China in 2019, accounting for around 3.6% of the total anthropogenic Hg release (including direct and secondary anthropogenic releases). It is worth noting that sludge treatment methods such as incineration, carbonization, and sludge/brick/cement manufacture pose the greatest threat to atmospheric Hg pollution [27]. Therefore, attention should be paid regarding Hg pollution of sewage effluents and standard regulations should be formulated in order to prevent the environment and human health.
