Driver: Pollution in the Puget Sound Basin

In its broadest sense pollution is often thought of as the introduction of unwanted or undesirable substances or conditions into the natural environment. Virtually all pollution types described in this section are unintended consequences of the daily activities of humans – driving cars, heating homes, growing food, building shelter, generating waste, manufacturing goods and so on. A Driver-Pressure-State-Impacts-Response (DPSIR) conceptual model is used here to help organize the complex information that describes these human activities and the pressures they create on the ecosystem (i.e. “Threats”). In addition it can provide context for discussing pollution-harm in the ecosystem and to humans, and the range of possible strategies we might employ to mitigate the threat (Figure 4).


Figure 4

Figure 4. Driver-Pressure-State-Impacts-Response conceptual model for Pollution in the Salish Sea ecosystem.

Human activities that generate pollution pressures can be organized according to the types of land use that generate characteristic pollution types, including urban, residential, commercial, agricultural activities. These can be overlain with cross-cutting activities (such burning fossil fuels) that occur virtually everywhere. Additionally, spills of chemicals, nutrients, soils, sediments or other unintentional episodic introductions of pollutants can cut across land use patterns.

Pollution occurs when human activities (a) generate toxic chemicals, (b) concentrate or make available naturally occurring substances to levels that can be harmful, (c) change conventional water quality characteristics (e.g., temperature) or (d) introduce disease pathogens or conditions that exacerbate diseases. In many cases pollutants may be generated or manufactured or released in one place and then transported to other areas where humans or biota in the ecosystem can be exposed to the pollutant. It is as important to understand these naturally occurring conveyance pathways such as stormwater, groundwater, air movement, and biological transport of pollutants because these are the mechanisms whereby pollutants move from their source to where they cause harm in the environment. In particular the degree to which stormwater or surface runoff patterns have been altered by human activities helps us understand how our actions may exacerbate or mitigate movement of pollutants in the environment.

The degree of potential harm or toxicity of the pollutant is related to the amount of the pollutant loaded to the system (the dose), the degree to which pollutants are subsequently concentrated in the environment, the fate and the sensitivity of the organism or ecosystem processes that are affected, and their ability to recover once the pressure is reduced (resiliency).

Although State, Impacts and Response components of this model are treated in detail in separate chapters of this Science Update, most definitions of Threat include some indication of harm to living organisms or ecosystem processes. Hence we include in this Threats Chapter some examples of harm related to pollution pressures, with greater detail on state and impact presented in Chapter 2a , Biophysical status of Puget Sound.

Placeholder - Pressure: Nutrients

Placeholder - Pressure: Increasing Atmospheric Carbon Dioxide

Placeholder - Pressure: Changing Temperature and Salinity

Placeholder - Pressure: Turbidity and Sedimentation

Placeholder - Pressure: Pathogens and Disease

Pressure: Toxic Contaminants in Puget Sound

The threat of pollution pressures in the Puget Sound Basin depends on where, when, amount, and type of contaminants that are loaded to the system (Figure 5). This section focuses on Washington’s inland marine and estuarine waters including Puget Sound’s main basins, Hood Canal, eastern Strait of Juan de Fuca, San Juan archipelago, and southern Strait of Georgia, (hereafter collectively referred to as Puget Sound), and the conveyance-pathways to that marine/estuarine system. Subsequent contributions to this Chapter will review toxic contaminants in freshwater systems, including the lakes, rivers, streams, wetlands and groundwaters that drain to Puget Sound or the Pacific Ocean.


Figure 5

Figure 5. Driver-Pressure-State-Impacts-Response conceptual model for Toxic Contaminants in the Salish Sea ecosystem.

Puget Sound’s fjord-like physiography, oceanographic isolation of some of its major basins, and relatively long water residence time may increase the susceptibility of its biota to contamination (Thomson 1994). Because the Sound possesses such a wide range of oceanographic conditions and habitats it also enables species that range from fully marine to diadromous to complete their entire life cycle within its waters, potentially exposing sensitive life stages to contamination.

Loading of Toxics to Puget Sound

The degree to which biota in the Puget Sound ecosystem are exposed to toxic contaminants depends on a complex interaction among the human activities that create the chemicals (e.g., land use, spills, burning fossil fuels), amounts and types of chemicals produced, and how they are conveyed to the ecosystem (Figure 5). Washington Department of Ecology (2010) have conducted or are currently conducting, sponsoring, or facilitating twenty studies designed to quantify loadings to and support the control of toxics in Puget Sound. These include inventories of chemicals of concern, estimates of chemical loadings to Puget Sound and the land-use activities that produce the chemicals, models of how chemicals move through the system, and evaluation of the fate and transport of these chemicals in the biological component of the ecosystem. Lubliner (2007) described some of these complex interactions within the context of estimating the total maximum daily load of chemicals to a water body.

Chemicals of Concern

Deciding which chemicals to evaluate is a daunting challenge: of the more than 53 million substances inventoried in the American Chemical Society’s Chemicals Abstract Service , over 100,000 have been registered for use in commerce in the USA. Only a relatively few have undergone much scrutiny or are regularly measured in the environment (Muir and Howard 2006). Their sheer numbers necessitate a scheme to select indicator chemicals that represent a wide range of chemical types.

The Washington Department of Ecology selected 17 Chemicals of Concern on which to focus evaluation of loadings to Puget Sound (Hart Crowser 2007). Selection criteria were based on concern for threats to biota or humans, chemicals that represent a broad range of conveyance pathways, and for which some monitoring data exist. This list includes a broad range of toxic contaminants that can be organized into logical groupings including metals (arsenic, cadmium, copper, lead, mercury and zinc); persistent bioaccumulative toxics (polychlorinated biphenyl ethers or PCBs, brominated flame retardants, or polybrominated diphenyl ethers [PBDEs], and chlorinated pesticides such as dichlordiphenyltrichloroethane and its metabolites [DDTs]); fossil fuels or their derivatives including polycyclic aromatic hydrocarbons (PAHs), oils and greases; one plasticizer (phthalates); nonylphenol, a suspected endocrine disrupting compound (EDC) and the herbicide triclopyr. Many of these pollutants are routinely measured by large-scale monitoring programs such as the national Mussel Watch Program (Kimbrough et al. 2008), and the Puget Sound Assessment and Monitoring Program for sediments (Dutch et al. 2009) and fish tissue (West et al. 2001), as well as regional monitoring programs such as King County’s marine water and sediment monitoring (King County 2010).

Chemicals of Emerging Concern (CEC)

CEC is a widely used term to categorize new environmental contaminants, as well as those that may have existed for some time, but whose threat is only now becoming known. Some CECs were included on Department of Ecology’s Chemicals of Concern list (Hart Crowser 2007), such as nonylphenol and bis(2-ethylhexyl) phthalate; others that are commonly discussed as threats include bisphenol-A, synthetic estrogen, and perfluorinated compounds, some of which are found in commercial goods, or may originate from the wide range of chemicals in pharmaceuticals and personal care products. Lubliner et al. (2010) measured 172 organic compounds including 72 pharmaceuticals and personal care products from three wastewater treatment plants that discharge to Puget Sound, and characterized the degree to which these chemicals are removed from wastewater or biosolids by various enhancements to secondary treatment. A number of these compounds exhibit endocrine disrupting properties, and are the focus of intense ecotoxicological research worldwide (Sumpter and Johnson 2005).

Synthetic polymers, or plastics, in the environment are a unique category of CEC because they not only pose multiple disparate threats to the ecosystem but also a unique conveyance mechanism for toxic chemicals from water to biota. Wildlife can be entangled by litter or harmed by ingestion of plastic debris, alien species can attach to and be transported by drifting litter, and benthic organisms be smothered by accumulation of plastics (see reviews in Derraik 2002, Moore 2008). In addition, the plastic itself can be toxic, and it can exacerbate exposure of organisms to other toxics. Plastic microparticles (<5mm) are created in the environment by degradation of larger litter (Thompson et al. 2004), or by the unintentional or intentional release of industrial microplastic stock. These particles can adsorb and concentrate contaminants from marine waters, including a number of toxics described earlier (Mato et al. 2000). Such particles can be subsequently ingested by a wide variety of marine organisms, thereby exposing consumers and creating a point of entry for water-column toxics to the food chain.

Conveyance Pathways of Toxics to Puget Sound

Hart Crowser (2007) cataloged nine important pathways or sources of pollutants to Puget Sound, many of which apply to freshwater systems as well:

  • Aerial transport – aerial contaminants can be deposited or recondensed to terrestrial or aquatic surfaces. These pollutants include not only direct inputs to the atmosphere from human activities (e.g., from driving cars) but also those already in the environment that may be evaporated, distilled or fractionated, and transported via atmospheric processes. (e.g., Simonich and Hites 1995).
  • Surface runoff – wherein stormwater carries terrestrially originating pollutants to receiving waters. Can be exacerbated by impervious surfaces (e.g., Lubliner 2007).
  • Groundwater discharge – wherein subsurface groundwaters carry pollutants to receiving waters
  • Discharges from industrial and municipal wastewater treatment plants (e.g., Lubliner 2010),
  • Discharges from combined sewer overflows
  • Direct spills (e.g., oil) to the system

Transport of pollutants in and out of Puget Sound by exchange with oceanic waters

  • Reintroduction of pollutants leached, resuspended, or concentrated into biota from contaminated sediments
  • Biological transport of pollutants (e.g., Ewald et al. 1998)

Surface runoff or stormwater is the primary conveyance for many toxic contaminants of concern in Puget Sound, and the ultimate source for the bulk of these toxics has been attributed to everyday activities of people in developed residential areas, rather than industrial or municipal discharges (EnviroVision et al. 2008). Pollution from runoff is the sum of contamination from many diffuse, “non-point,” sources. As such it is difficult to characterize, evaluate or control. The PEW Oceans Commission (2003) characterized non-point source pollution as “…the greatest pollution threat to our oceans and coasts… the situation requires that we apply new thinking about the connection between the land and the sea, and the role watersheds play in providing habitat and reducing pollution.”

Point source releases such as a discharge pipe release monitored and known amount of contaminants into receiving waters. The National Pollution Discharge Elimination System (NPDES) is designed to control pollutants at such point sources to protect water quality for drinking, fishing, swimming and other activities. All discharges to waters of the State must have an NPDES permit, which includes municipal and industrial wastewater, stormwater from certain jurisdictions, and general permits to cover a variety of other activities.

A large oil or other chemical spill poses a singular and significant threat to Puget Sound. Over 20 billion gallons of oil and other toxic chemicals are transported through Washington State by various means annually (Jensen 2009). Schmidt-Etkin (2009) reported the greatest potential risks of a worst-case oil spill in Puget Sound come from oil tankers, cargo vessels and oil barges. The largest oil vessels entering Puget Sound can carry up to 35,000,000 gallons of oil (OSAC 2009). Although the probability of a large oil spill from these vessels is relatively low, a large spill could have devastating, long-term impacts to natural and cultural resources in Puget Sound. Washington state efforts relating to oil or other chemical spills are focused on spill prevention, preparedness and response.

Losses/removal of toxic contaminants from the ecosystem - Placeholder

  • Burial
  • Degradation/detoxification
  • Dilution/mixing
  • Biological transport

Other Pathways (placeholder)

  • Recycling to and from sediments
  • Movement between water bodies
  • Biological transport
  • Trophic transfer (e.g., biomagnification)


1. State and Impact in the Ecosystem

By its definition, threat implies harm to biota, humans, or ecosystem function. The Toxic Contaminants DPSIR conceptual model helps to link the threat from human activities, contaminants sources, loadings, and conveyance pathways to the states of ecosystem health that are of concern (Figure 5). Contaminant states can be measured in biota as exposure, or concentration of contaminant residues in tissues, presence of contaminant metabolites or toxicopathic disease. Contamination of sediments and water are also often measured as a proxy for biota-exposure, based on known or surmised bioconcentration or bioaccumulation factors (e.g., see Johnson et al 2002).

Sediment Health - placeholder

  • Sediment quality triad, a unique multimetric index of sediment quality that combines toxic contaminants, toxicity, and infaunal community characteristics

2. Biota Health

Once released into the environment, many chemicals of concern can persist for long periods of time and contaminate extensive areas. Chapter 2a summarizes major aspects of the distribution of toxic contaminants in Puget Sound’s abiotic media (primarily sediments) including a the sediment quality triad, a multimetric evaluation of sediment quality related to toxic contamination. The degree to which biota are threatened by toxic contamination relates to all the complexities described in the Driver-Pressure-Conveyance above, combined with the susceptibility and sensitivity of organisms to exposure, the fate and transport of toxics in the environment and in the food web, the degree to which chemicals accumulate in tissues or are metabolized, and how resilient biota are once the pressure is removed.

Impacts to biota can be measured as direct health impairments to individuals e.g., mortality, immunosuppression, reduced fitness, or reproductive impairment that may ultimately impact populations, or as indirect effects wherein community structure may be altered because of toxicopathic losses of individuals. These latter impacts have been observed in benthic infaunal micro-invertebrates in Puget Sound (Long et al. 2005) but have been difficult to observe in higher organisms. Toxicopathic community effects in higher organisms such as fishes, birds and mammals are often modeled as cascade effects in the ecosystem based on known predator-prey or competitive relationships among affected species.

3. Persistent Bioaccumulative Toxics (PBTs)

Because many chemicals are persistent, bioaccumulative toxics (PBTs) understanding their fate and transport in the environment including movement in the food web is of paramount interest in evaluating threats. As reviewed in Chapter 2a, mammalian apex predators such as killer whales (Orcinus orca) and harbor seals (Phoca vitulina) have exhibited body burdens of persistent toxics (PCBs and PBDEs) expected to cause serious health effects (Ross 2006). Ross et al. (2000) characterized the Southern Resident Killer Whale population as among the most contaminated cetaceans in the world. Exposure to PBTs have been implicated as a cause for population decline in this population, as well as an impediment to their recovery (Krahn et al. 2002). PBT exposure in apex predators like these is widely thought to occur from consuming contaminated prey (Cullon et al. 2005, Cullon et al. 2009, O'Neill et al. 2006). The most highly PCB-contaminated populations of killer whale and harbor seal prey -- chinook salmon (O'Neill and West 2009) and Pacific herring (West et al. 2008) -- have been reported from Central and Southern Puget Sound.

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Placeholder - Dioxins/furans

Toxicopathic Impacts: three cases studies

The DPSIR conceptual model implies a left-to-right progression of thought and discovery from drivers to impacts. This type of model has directed a great deal of monitoring and assessment efforts to date in Puget Sound, including the PBT studies in fish and mammals described above. In some cases however, toxicopathic impacts have been identified in biota first, without knowledge of or understanding the drivers or pressures or conveyance pathways. In such cases, scientists have worked right-to-left from impacts to identify causative chemicals, pathways and sources. This approach requires field-biological capacity that can “…pay attention to unusual biological observations..”, recognizing “…what is normal and abnormal…” (sensu, Sumpter and Johnson 2005) within the context of the range of stressors (pollution or other) that might cause such abnormalities. Three prominent indicators of biota health in Puget Sound that were developed in this manner are reviewed here as case studies.

Case 1: Cancerous liver tumors were observed in English sole (Pleuronectes vetulus), a bottom-dwelling flatfish, in Puget Sound’s most polluted waters as early as 1975. At that time the disease was hypothetically linked to pollutant exposure. This cancerous biomarker has been used since that time as an indicator of bottomfish health in Puget Sound, and its cause has been identified as exposure to fossil fuels or by-products of their use (polycyclic aromatic hydrocarbons or PAHs -- Myers et al. 2003). Liver disease in English sole is being used to track efficacy of a sediment-PAH cleanup program in Eagle Harbor (Myers et al. 2008), and is currently being monitored along with sediment PAHs in Puget Sound to evaluate trends in ecosystem health Sound-wide. The disease is significant to fish because it is associated with reproductive impairment and liver disease that have fitness consequences (Johnson & Landahl 1993). One study suggested the level of impairment exhibited by English sole could reduce population size in exposed populations in Puget Sound (Johnson et al. 1998).

Case 2: Threats to bottomfish populations related to exposure to endocrine disrupting compounds (EDCs) have been identified in Puget Sound. Initially recognized in routine field monitoring efforts as abnormal gonadal development, specific toxicopathic reproductive anomalies such as abnormal spawn timing in male and females and feminization of male fish were later identified in English sole from Elliott Bay (Johnson et al. 2008). These authors noted that several EDC compounds that could cause these conditions have been identified in Elliott Bay sediments (Partridge et al., 2005), in watershed bodies, stormwater, and wastewaters draining to Elliott Bay. These compounds include both natural human estrogen (17-β estradiol) and synthetic estrogen (ethinylestradiol), which can be conveyed to aquatic systems via wastewater treatment plants in Puget Sound (Lubliner 2010), as well as nonylphenol (a surfactant commonly found in detergent) and bisphenol A (commonly found in polycarbonate plastics), which have been measured in stormwaters draining to Puget Sound (King County 2007).

Case 3: Contaminant threats to coho salmon (Oncorhynchus kisutch) spawning in urbanized, lowland stream reaches have been described from years of observing “pre-spawning mortality” of this species (McCarthy et al. 2008), wherein adults returning to spawn in such streams die before they can spawn, sometimes within a few hours of entering the stream. This threat is of particular concern because it affects a sensitive life history phase during reproduction, as coho salmon are moving from saltwater back to freshwater to spawn. This syndrome is associated with storm-related flash-flow regimes in lowland urban streams that receive stormwater draining from urban landscapes. Stormwater-conveyed contaminants and sedimentation have been implicated as causative, especially stormwater that occurs after a long antecedent dry spell.

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4. Uncertainties and Information Gaps

The threat of toxics is related not only to the source, fate and transport of toxics in the environment, but also to the toxicity and subsequent harm to organisms. Significant uncertainties and knowledge gaps exist in all of these areas. Washington State agencies are currently placing a high emphasis on quantifying the type, loading amounts, and timing of toxic contaminants entering Puget Sound, especially via stormwater, and modeling the movement of toxics in the ecosystem. These ongoing efforts produce valuable estimates of contaminant loadings and information on how contaminants reach Puget Sound. In addition, this effort will produce associated estimates of uncertainty, which should be carefully considered in management responses.

Significant uncertainty also relates to gaps in knowledge, including:

  • where and when accumulative toxics enter the food chain,
  • temporal and spatial trends in biota-exposure for many contaminants, and
  • the relative harm to biota and humans caused by exposures.

As described in Chapter 2 Biophysical status of Puget Sound, some of the greatest uncertainty regarding the threat of toxic chemical contaminants in the Puget Sound ecosystem is how toxics affect or harm organisms. Although there exists a great deal of information related to the extent and magnitude of exposure of Puget Sound biota to toxic contaminants, significant gaps in our understanding of how toxics harm biota include:

  • toxicity of multiple-chemical mixtures,
  • sublethal effects on reproduction and fitness,
  • population-level effects,
  • community-level effects related to changes in fitness and cascading competition and predation effects among affected species,
  • realistic effects-thresholds for most Chemicals of Concern,
  • the relative degree of threat for the wide range of toxics we are aware of, and
  • exposure and effects in sensitive life-stages (such as eggs, larvae, and reproducing adults).

Careful selection of indicator species and metrics that can be used to evaluate these gaps will allow better understanding of where to focus limited recovery resources, as well as predict outcomes from recovery strategies.

Placeholder - Pressure: Toxic Chemical Contaminants in Freshwaters

  • Ecology PBDE study
  • Ecology Mercury/human health study
  • Ecology PCB study?
  • King Co. DNR Lake Washington EDC study
  • NOAA salmon studies
  • Copper
    • Current use pesticides



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