reuenc of detection 


State and trends


of zooplankton, trending toward less Ca-rich (and less nutritious) species with potential impacts for aquatic food webs (Jeziorski et al. 2015).


Metals


Metal pollution in freshwater lakes has been generally decreasing across the US. In a study of lakes, decreasing trends outnumber increasing ones for the seven metals analysed, cadmium, chromium, copper, lead, mercury, nickel and zinc. The most consistent trends are for lead and chromium: for lead, 83 per cent of the lakes are decreasing and 6 per cent increasing; for chromium, 54 per cent of the lakes are decreasing and none are increasing (Mahler et al. 2006).


Contaminants of emerging concern


Municipal and industrial wastewater management in North America has achieved relatively consistent and good treatment of traditional pollutants such as ammonia and biological oxygen-demanding matter. However, wastewater treatment systems were not designed to remove an emerging group of contaminants associated with personal care products, pharmaceuticals, and other compounds common in residential, industrial, and agricultural life.


Contaminants of emerging concern have been documented in waters across North America, including in streams, untreated drinking-water sources in the ground and on the surface, and the Great Lakes Basin (Focazio et al. 2008; Blair et al. 2013; Hull et al. 2015). In 2000, the US Geological Survey (USGS) identified contaminants of emerging concern in 80 per cent of streams sampled. The most frequently detected compounds were coprostanol (faecal steroid indicating sewage contamination), cholesterol (plant and animal steroid), N,N-diethyltoluamide (insect repellent), caffeine (stimulant), triclosan (antimicrobial disinfectant), tri (2-chloroethyl) phosphate (fire retardant), and 4-nonylphenol (non-ionic detergent metabolite) (Kolpin et al. 2002; Figure 2.4.18). More recently, a US survey of untreated drinking water sources (25 groundwater sites and 49 surface waters)


Source: Kolpin et al. 2002


showed that 63 of the 100 targeted chemicals were detected in at least one sample but that more than 60 per cent of the 36 pharmaceuticals examined were not detected in any of the waters sampled (Focazio et al. 2008). Although the environmental threat they pose in large lake systems has previously been considered minimal due to dilution, Blair et al. (2013) indicate that concentrations of 14 of these contaminants pose a significant threat to the health of the Great Lakes, especially to organisms found near shorelines. The persistence of chemicals found in the Great Lakes is demonstrated by measurable concentrations of pesticides that are no longer registered for use in North America, such as azinpho-methyl (Hull et al. 2015).


Understanding the effects of CECs on human health and the environment and developing treatment techniques and other technologies to mitigate their impacts is a top priority for North America. Additional information on CECs is available in section 2.6.1 and the North American Outlook (Chapter 4).


89


Figure 2.4.18: Frequency of detection of organic wastewater contaminants by general use in US streams, 2002


10 0 4


80 6 0


5


4 0 20


6 0 1 5 3 7


2 22 7 11 14 5 2 1


S t e r o i d s


Nonprescription drugs I n s e c t r e p e l l e n t


etergent metabolites isinfectants plasticizers


ire retardants ntibiotics nsecticides


P A H s eproductive ormones


Oter prescription drugs ntioidants


ragrances Solvent


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