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HEALTH CONSULTATION

CALCASIEU PARISH (CALCASIEU ESTUARY)
LAKE CHARLES, CALCASIEU PARISH, LOUISIANA


DISCUSSION

Dioxin-like compounds are widespread environmental contaminants and have been detected in human blood, fat tissue, and milk. Using a sensitive analytical methodology, dioxin-like compounds can be detected in almost all residents of industrialized and non-industrialized countries. The major source of exposure to dioxin-like compounds in the general population is from food (beef, dairy products, and fish), with smaller exposures from air, water, and soil [5]. Based on available data, it has been reported that concentrations of dioxin-like compounds in humans do not vary significantly by race, gender, or geographic region; however, concentrations of dioxin-like compounds do increase with age [5].

Numerous studies have reported blood levels of dioxin-like compounds detected in human populations. However, to date, no large-scale study of the levels of dioxin-like compounds in a statistically-based sample of the United States population has been conducted. The National Center for Environmental Health conducted a comprehensive survey of published studies and compiled data from studies of people who had presumably not been occupationally exposed to these chemicals [2]. In this health consultation, blood levels of TCDD and other dioxin congeners were compared to this compilation of reference ranges.

In the general population, it has been estimated that average TEQ concentrations range from 28-41 ppt for dioxin-like compounds and from 36-58 ppt for dioxin-like compounds plus PCBs [3]. These ranges were used as reference ranges for this health consultation.

As indicated by the data in Table 1, a pooled blood sample contained TCDD and dioxin TEQs in excess of the reference ranges, and the TEQs+PCBs were at the upper end of the reference range. This sample was composed of blood aliquots from 100 patients at St. Patrick's Hospital and was intended to represent the average, background concentration of dioxin in residents of Calcasieu Parish. No information is available on the individuals who made up this composite, so it cannot be concluded that the dioxin level in this sample is representative of the community.

The dioxin concentration in the pooled blood sample is, in effect, an average concentration for the population tested. Therefore, blood TCDD and dioxin TEQ concentrations in this population of Calcasien residents are higher than those in the general population.

Blood dioxin concentrations in 11 non-randomly selected residents are reported in Table 1. As indicated, three of the individual samples had concentrations of TCDD, TEQs, or TEQs+PCBs that exceeded the reference ranges. The congener specific profile for the Calcasien resident with the highest dioxin levels is shown in Table 2. As indicated, TCDD, as well as several other higher chlorinated CDDs and CDFs, were elevated above reference levels.

The health impact, if any, of these elevated dioxin levels cannot be determined. Available data suggest that body burdens of dioxin within one to two orders of magnitude of those in the general population may be associated with cancer and noncancer health effects [3]. However, no "safe" level for a body burden of dioxin has been determined. Therefore, it would be prudent public health policy to reduce exposure to environmental sources of dioxin in individuals with elevated levels.

Sediment

Sediment samples from 9 locations contained dioxin TEQ concentrations ranging from 0.0023 to 2.958 ppb dry weight. For soil in residential areas, ATSDR typically recommends that dioxin concentrations should not exceed 1 ppb; ATSDR has not derived a recommended level for dioxin in sediment. However, the levels of dioxin detected in sediment are unlikely to pose a public health hazard because of limited opportunity for human contact with the sediment. Nevertheless, dioxin in sediment may be a source for bioaccumulation by fish, clams, and other edible biota in affected bodies of water.

Biota

A composite clam sample contained 51.6 ppt dioxin TEQs, fat based, which is equivalent to 0.24 ppt, wet weight. In a national survey that included contaminated as well as non-contaminated areas, the EPA reported that the average concentration of dioxin TEQs in fish was 11 ppt, wet weight [5]. In clams from a dioxin-contaminated area (Newark Bay, New Jersey), dioxin TEQs ranged from 13-25 ppt; in clams from an uncontaminated area (Little Egg Harbor, New Jersey), dioxin TEQs ranged from 1.2-2.1 ppt [6]. These concentrations significantly exceed the concentration of dioxin TEQs (0.24 ppt) detected in the clam composite from Lake Charles. Therefore dioxin TEQs in calms from Lake Charles were not elevated relative to fish and clams from the rest of the country.


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