Food Fish
Chapter 1
GLOBAL GENDER AND ENVIRONMENT OUTLOOK Chapter 4: Water Forest
Methyl mercury: Methyl mercury is a heavy metal found in large quantities in marine systems. It originates primarily from land-based industrial emissions, coal burning and mining processes. For humans, consumption of fish and shellfish is the primary route of exposure. Once introduced into marine systems, in fish and shellfish it bioaccumulates, often at concentrations 1-10 million times higher than in ambient water (US EPA 2015; Lawrence and Mason 2001). In humans methyl mercury is a strong neurotoxin with severe health implications such as kidney and brain damage. Foetal exposure in utero is especially problematic, often resulting in neurodevelopmental problems in children (Axelrad et al. 2007; Weihe et al. 2002). Many governments and health authorities worldwide issue fish advisories to warn consumers, especially pregnant women, about the dangers of mercury exposure through fish consumption (Figure 2.5.2).
Energy Chapter 2
In the northern hemisphere, ocean currents tend to drive methyl mercury contamination northward towards
the Arctic, where it becomes further
concentrated in large marine mammals. Some of the highest human concentrations are found in indigenous children (especially those still breastfeeding) in the Canadian Artic and northern Greenland, in populations that depend heavily on fish and marine mammals for sustenance (El-Hayek 2007). Methyl mercury contamination is not limited to northern zones: high levels have been widely reported in coastal Peru, New Zeland and the Seychelles, among other countries (Dewailly and Knap 2006).
Sewage 138
Sewage entering the marine system through sewage treatment outputs, storm water run-off and direct dumping of raw sewage is a source of considerable ocean and coastal pollution globally (Islam et al. 2013). Many of the world’s cities do not treat (or only partially treat) sewage (Table 2.5.2). The regional district of Victoria, Canada, for example, pumps 120-130 million litres per day of raw sewage into the nearby Strait of Juan de Fuca (Meissner 2014); Zanzibar (Tanzania), with a population of over 1 million, has no sewage treatment plant (IRIN News 2010); only 40% of sewage in Rio de Janeiro is treated, with the remainder flowing directly into marine systems (Hosek 2013); 80% of urban sewage discharged into the Mediterranean Sea (an estimated 650 million tonnes per year) is untreated in Accra, Ghana, 1000 tonnes of sewage per day is
Figure 2.5.2: Public warning about seafood for women and children
Source: United States Food and Drug Administration. Reproduced in Chai (2014)
dumped into the sea (Hinshaw 2012). As sea level rise continues and coastal populations grow, the impacts of sewage dumping on human health and the health of marine ecosystems will continue to escalate.
Lack of sewage treatment in many parts of the world is related to the high costs of infrastructure, which may be beyond the reach of most municipal or federal budgets in developing countries. However,
it also
reflects widespread cultural and political complacency about oceans’ capacity to absorb vast quantities of human pollution.
Table 2.5.2: Percentage of sewage treated, by region Region
North America Europe Asia
Latin America & Caribbean
Africa
Percent of Sewage Treated 90 66 35 14
<1 Source: World Resources Institute (n.d.)
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