A recent soil study by Public Health - Seattle & King County funded by the Washington State Department of Ecology (Ecology) found elevated levels of arsenic and lead in the soils of Vashon-Maury Island as well as at sites along the mainland shoreline of King County between West Seattle and the southern King County line. The levels of arsenic exceed the residential soil cleanup level of 20 ppm set by Ecology in the Model Toxics Control Act Regulations.

Although soil arsenic levels are elevated, it is important to recognize that the Ecology soil cleanup level does not indicate that an imminent health hazard exists to residents or workers. A recent analysis of the data by Industrial Hygienists indicates that airborne and skin exposures to soils in the Vashon-Maury Island and mainland coastline area will not result in significant occupational exposures during construction-related activities, provided that existing dust suppression requirements are followed.

Arsenic

Arsenic is a naturally occurring element. Pure arsenic is a gray metal-like material that is usually found in the environment combined with other elements such as oxygen, chlorine, and sulfur. Arsenic combined with these elements is called inorganic arsenic. Arsenic combined with carbon and hydrogen is called organic arsenic. Understanding the difference between inorganic and organic arsenic is important because the organic forms are usually less harmful that the inorganic forms.

Most inorganic and organic arsenic compounds are white or colorless powders that do not evaporate. They have no smell, and most have no special taste. Thus, you usually cannot tell if arsenic is present in your food, water, or air.

Arsenic in Washington

Inorganic arsenic occurs naturally in many kinds of rock, especially in ores that contain copper or lead. A recent study done by the Ecology and the United State Geological Survey (USGS) determined the natural background levels for Arsenic (As), Cadmium (Cd) and Lead (Pb). The natural background levels of arsenic in soil statewide and in Puget Sound are typically below 7 ppm.

In 1999, Public Health -- Seattle & King County sampled background soils on Vashon-Maury Island and the mainland under a grant from Ecology. Results from this sampling and analysis show background levels of arsenic that are predominantly above the Ecology's Model Toxics Control Act residential standard of 20 ppm, and occasionally above the industrial standard of 200 ppm.

The 417 soil samples analyzed came from 3 zones: 248 from South Vashon & Maury in Zone 1, 48 from the mainland in Zone 2, and 121 North Vashon in Zone 3.

Test results indicate ranges and mean (average) for arsenic as follow.

ZONE	SAMPLE #	RANGE	MEAN
1 (S Vashon/Maury)	248	8 to 460 ppm	85 ppm
2 (Mainland)	48	5 to 260 ppm	44 ppm
3 (N Vashon)	121	ND to 140 ppm	28 ppm

Occupational Hazards

Because of the preliminary findings of the soil tests, King County Safety & Claims Management issued an analysis called "Occupational Health Risk Screening of Arsenic Exposure During Site Clearing and Soil Grading Activities South Vashon & Maury Islands". The evaluators are Certified Industrial Hygienists. Their evaluation assumes that the worst-case soil levels are present in the same proportions in the total dust in the air.

The results from the worst-case evaluation process indicate that workers on the island would not be exposed to arsenic above the "Permissible Exposure Limit". The "Permissible Exposure Limit" for arsenic (0.01 milligrams per cubic meter in air) is regulated by the Washington Department of Labor and Industries.

While soil arsenic levels are elevated relative to typical background levels for this areas, it is important to recognize that the WSDOE action level of 20 ppm represents a need for further study, and does not indicate that an imminent health hazard exists to residents or workers. Based on the observation that elevated arsenic is limited to surface soils (primarily the upper six inches) it is highly unlikely that arsenic has entered groundwater used for drinking water purposes. In addition, airborne exposures to residents would be far lower that the hypothetical worst-case occupational exposures evaluated herein.

It is important to recognize that inorganic arsenic is a cumulative poison. Although It can cause acute toxic effects after one large dose The greater concern, however, is that inorganic arsenicit can cause chronic toxic effects as a result of repeated small doses over a prolonged period of time. The occupational Permissible Exposure Limit is intended to protect workers who are exposed to inorganic arsenic 40 hours per week over a working lifetime.

In summary, the analysis indicates that airborne and skin exposures to soils in the Vashon-Maury Island and mainland areas will not result in significant occupational exposures to King County employees engaged in their routine job duties or typical construction-related activities, provided that existing dust suppression requirements are followed. Over the next several weeks the King County Division of Safety and Claims Management will measure airborne arsenic concentrations on a representative group of King County employees and of the ambient air to the extent necessary to evaluate this initial assessment.

Other employers must contact the state of Washington, Department of Labor and Industries for information about the Occupational Health requirements for the job duties their employees may perform. The phone number for Seattle Office of the Department of Labor and Industries is (206) 281-5470.

Questions have arisen about wearing personal protective equipment sometimes required under Washington's Hazardous Waste Operations and Emergency Response (HAZWOPER) regulation. Protective equipment is not required; however, several precautionary actions are recommended: