DDT, Chlordane, Toxaphene and PCB Residues in Newport Bay and Watershed: Assessment of Hazard to Wildlife and Human Health - Reviews of Environmental Contamination and Toxicology - page 136

These concepts were known as early as the late 1960s, explaining, in part, why
the U. S. Food and Drug Administration set the action level for DDTs in commer-
cial fi sh at 5,000 ppb. That action level is still in effect today (US FDA 2007 ).
The OEHHA guidance dealing with the risk of human cancer from ingestion of
sport fi sh fi llets has been misinterpreted to claim impairment of benefi cial uses of
Newport Bay. However, even the 1/100,000 potential risk level is met by those
ingesting sport fi sh from Newport Bay. As reported in the Allen et al. ( 2004 ) study,
a survey among local anglers identifi ed the most sought after species of fi sh. Four of
the top fi ve were analyzed for DDTs. Total DDT residues in these four species by
preference rank were 69, 68, 64 and 84 ppb. The average DDT residue in 14 species
of sport fi sh was 79 ppb. These fi sh were captured in 2000 and 2001. The levels
today are almost certainly lower. Considering these residue levels in sport fi sh fi l-
lets, the 520 ppb target is met and even the older guidance of 100 ppb is met. There
is no impairment of sport fi shing in Newport Bay.

4 Chlordane

4.1 Levels in the Environment

The following sections present available chlordane data for Newport Bay and
Watershed. Downward trends in chlordane concentrations—particularly in fi sh tis-
sue and mussel tissue—are evident in data collected for almost 20 years.

4.1.1 Agricultural Soils

The half-life of chlordane in soil is estimated at 350 days (or approximately 1 year),
but can range from 37 to 3,500 days (approximately 10 years) (Hornsby et al. 1996 ).
Chlordane is persistent in soils and volatilization is believed to be the major removal
mechanism (US DHHS 1994 ). Chlordane data for agricultural soil are available for
the Newport Bay watershed for the years 1989, 1990, 1995, 2000, 2002, 2004 and
2006 (Table 28 ).
Samples were taken from different locations and different years with the purpose
of assessing site conditions for planning and development and not to establish con-
centration trends over time in the Watershed. The vast majority (approximately
95%) of chlordane soil samples returned concentrations below detection limits.
Detectable concentrations ranged between 47 and 240 ppb.