AQ Monitoring Results: Crockett: Arsenic at John Swett

This page last reviewed September 01, 2010

Background

Arsenic is a metallic element with three allotropic forms, yellow, black, and gray, of which the brittle, crystalline gray is the most common. Arsenic exists as both organic and inorganic compounds. The majority of atmospheric arsenic is inorganic arsenic. Through injection, inhalation and skin permeation, arsenic can cause minor to serious health effects. California has determined under Assembly Bill 1807 and Proposition 65 that inorganic arsenic compounds are cancer-causing compounds. Non-cancer effects from arsenic exposure include irritation of the eyes, nose and bronchi, vascular disorders (hemolysis), neurological disturbances, adverse reproductive effects, and liver or kidney damage.

Combustion and high-temperature processes are the largest sources of inorganic arsenic emissions to the atmosphere. Arsenic is used in metallurgy for hardening copper, lead, and alloys. It is also used in the manufacturing of certain types of glass. The primary industrial sources of arsenic in California are electrical services and metal mining. Arsenic and its compounds are also used in insecticides, weed killers, fungicide and wood preservative. Indoor arsenic sources include tobacco smoke, and burning of wood treated with arsenic wood preservatives. One cigarette typically contains 40 to 120 nano-grams of arsenic.

Arsenic composes small percent of the earth's crust. Inorganic arsenic can be released into the air by volcanoes and the weathering of arsenic-containing minerals and ores. Due to natural geo-chemical enrichment in California, arsenic is found in both above ground and below ground drinking water, and total exposure to arsenic from drinking water is usually far higher than total exposure from inhalation from the ambient air.

The Air Resources Board adopted an airborne toxic control measure in 1993 for non-ferrous metal melting operations. This control measure is expected to reduce emissions of arsenic. From year 1990 to year 2000, the average arsenic concentration in California has reduced approximately by 6 percent.


Ambient Monitoring Results

Ambient levels of arsenic are routinely monitored at approximately twenty sites in the California air toxics monitoring network. The statewide average concentration of arsenic during 1998-2000 was 1.66 ng/m3 (nanograms per cubic meter), with values ranging from 1.5 ng/m3 to 18.0 ng/m3. The current routine monitor closest to Crockett is in Fremont. Relative to the statewide average, the Fremont region was 8% lower, with an average concentration of 1.52 ng/m3 for the same time period. In the monitoring done at John Swett through February 2003, most of the values measured for arsenic were below the limit of detection.

The ambient monitoring results at John Swett are provided here:

  • A graph comparing the monthly summaries of arsenic at the community with historical statewide and regional levels
  • A table of summary statistics
  • Raw data in Excel format

Cancer Risk

Cancer risk is the number of excess cancer cases among a million people if the people are exposed to levels of a toxic air pollutant over 70 years. Arsenic is equivalent to less than 1% of the potential cancer risk of the nine measured compounds and the estimated diesel particulate matter.


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