Toxic Chemicals in Puget Sound photo identifier

Toxic Chemicals in Puget Sound

Loading Quantities

The Toxics Assessment estimated the “loading” amount of each chemical entering the Puget Sound basin per year from major pathways. Loading is the annual amount of a chemical estimated to reach Puget Sound itself and the waters that drain to the Sound from a particular pathway.

Not all toxic pollutants reach Puget Sound and the waters that drain to it. Environmental process such as dilution, deposition and degradation can reduce concentrations of toxic pollutants as they move away from their sources.

In general, loadings were about 10 to 1,000 times smaller than estimated releases from Sources. Arsenic is an exception to this observed pattern — most likely due to the presence of natural sources or historical releases.

The hazard each chemical poses depends on how toxic it is as well as the amount entering the Puget Sound environment. For instance, even a small amount of copper interferes with a salmon’s sense of smell, making it harder to avoid predators.

As a result, copper presents a significant threat even though the estimated loading quantities for copper — between 33 to 80 metric tons a year — are much smaller than for other chemicals, such as petroleum-related compounds estimated to be between 330 to 500 metric tons a year.

The table below summarizes the estimated loading for each chemical and the major pathway. Except where noted, the loading estimates are expressed in metric tons per year. One metric ton is approximately 2,200 pounds.

Chemical of ConcernTotal Load to Puget SoundA,BMajor Pathway(s)
Arsenic14 – 25Surface Runoff
Cadmium0.05 – 0.53Groundwater
Atm. Deposition
CopperC33 – 80Surface Runoff
Lead3.6 – 12Surface Runoff
Mercury0.11 – 0.37Surface Runoff
Zinc140 - 200Surface Runoff
Total PCBs0.003 – 0.02Surface Runoff
Total PBDEs0.028 – 0.054Atm. Deposition
Total DDT0.0025 – 0.032Surface Runoff
Total PAHsE0.19 – 1.0Groundwater
Surface Runoff
DEHP2.0 – 3.2Surface Runoff
Triclopyr0.64 – 0.69Surface Runoff
NonylphenolD0.023 – 0.024Surface Runoff
Petroleum330 – 500Surface Runoff
Oil & GreaseE8,500 – 11,000Surface Runoff

NA =   Not analyzed
A   Includes the Puget Sound and the U.S. portions of the Straits of Georgia and Juan de Fuca.
B   Range of all pathways combined expressed as the sum of the 25th percentile values for each pathway – sum of the75th percentile values for each pathway.
C   Does not include estimated direct releases to marine waters (54 metric tons/yr for PAHs and 26 metric ton/yr for copper).
D   Sources were not fully assessed.
E   Category includes all hexane extractable material

Assessment of Selected Toxic Chemicals in the Puget Sound Basin

Assessment of Selected Toxic Chemicals in the Puget Sound Basin: 2007—2011

Focus on Puget Sound: Puget Sound Toxics Assessment

Frequently Asked Questions