AQ Monitoring Results:
Crockett: Para-Dichlorobenzene at John Swett
This page last reviewed September 27, 2010
Atmospheric para-dichlorobenzene vaporizes directly into the air from its solid crystal form. The crystals are white, volatile, and non-corrosive, with a penetrating odor. Through inhalation, ingestion, and dermal contact, para-dichlorobenzene can irritate the skin, eyes, and respiratory tract. Long-term inhalation exposure may affect
the liver, skin, and central nervous system. California has determined under Assembly Bill 1807 and Proposition 65 that para-dichlorobenzene is a cancer-causing compound.
Para-dichlorobenzene is used as a room deodorant, a dye intermediate, and a registered insecticide. These sources account for approximately 99% of statewide para-dichlorobenzene emissions. Since para-dichlorobenzene is used as a room deodorizer and for moth control, volatilization from these products that are nearly pure para-dichlorobenzene is the most significant indoor source. There are no identified natural sources of para-dichlorobenzene.
Based on the statewide annual average, ambient para-dichlorobenzene concentrations remained fairly constant during the 1990s.
Ambient Monitoring Results
Ambient levels of para-dichlorobenzene are routinely monitored at approximately twenty sites in the California air toxics monitoring network. The statewide average concentration of para-dichlorobenzene during 1998-2000 was 0.1 ppb (parts per billion), with values ranging from 0.1 ppb to 1.9 ppb. The current routine monitor closest to Crockett is in Fremont. Relative to the statewide average, the Fremont region was 10% higher, with an average concentration of 0.11 ppb for the same time period. In the monitoring done at John Swett through May 2003, all the values measured for para-dichlorobenzene were below the limit of detection.
The ambient monitoring results at John Swett are provided here:
- A graph comparing the monthly summaries of para-dichlorobenzene at the community with historical statewide and regional levels
- A table of summary statistics
- Raw data in Excel format
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. Para-dichlorobenzene represents approximately 9% of the potential cancer risk of the nine measured compounds, excluding diesel particulate matter. Para-dichlorobenzene represents approximately 2% of the potential cancer risk of the nine measured compounds and the estimated diesel particulate matter.