Radiocesium in fish from the Savannah River and Steel Creek: potential food chain exposure to the public.

This study examined radiocesium (137Cs) levels in fish from the vicinity of the Department of Energy's Savannah River Site (SRS), a former nuclear weapons production facility in South Carolina. Fish from the Savannah River were sampled above (upstream), along, and below (downstream) the SRS, and from Steel Creek, a tributary that runs through the SRS. There was some off-site contamination of 137Cs in the Savannah River watershed due to low-level releases from past nuclear production on the SRS. The null hypotheses tested were that there would be no differences in 137Cs levels as a function of location along the river, and between species collected from the river and from Steel Creek on the SRS. For six of eight species of fish collected from the Savannah River, there were no differences in 137Cs levels in muscle from fish collected above, along, or below the SRS; exceptions were bowfin and shellcracker. Fish collected from Steel Creek had significantly higher levels (by about an order of magnitude) of 137Cs in muscle tissue than fish collected in the Savannah River. However, no fish from either Steel Creek or the Savannah River had 137Cs levels above the European Economic Community limit for fresh meat of 0.6 Bq/g. Lifetime cancer risk was calculated using the cancer slope factor of 3.2 x 10(-11)/pCi, and various fish consumption scenarios reflecting actual data from Savannah River fishermen. Using mean 137Cs concentrations and median fish consumption for 70 years for Black males-the group with the highest consumption-the excess lifetime risk associated with the eight species of fish in the Savannah River ranged from 9.0 x 10(-7) to 1.0 x 10(-5). The same calculation for fish from Steel Creek gave risk estimates from 1.4 to 8.0 x 10(-5). The 95% level for consumption by Blacks, however, was about 70 kg/year. Black fishermen consuming that amount of bass from Steel Creek would sustain a lifetime risk of 3.1 x 10(-4), whereas the same consumption of Savannah River bass would yield a risk estimate of 1.5 x 10(-5).

Ecological half-life of 137Cs in fish from a stream contaminated by nuclear reactor effluents.

Radiocesium (137Cs) concentrations were determined during 1974, 1981 and 1998 for seven species of fish inhabiting a stream (Steel Creek) contaminated by effluents from a nuclear reactor to examine the decline of this radionuclide in a natural ecosystem. Median 137Cs concentrations were highest in Micropterus salmoides (largemouth bass) during each year of the investigation (1974 = 6.67 Bq g(-1) dry wt. of whole body; 1981 = 3.72 Bq g(-1); 1998 = 0.35 Bq g(-1)), but no patterns of differences were observed among Aphredoderus sayanus (pirate perch), Esox americanus (redfin pickerel), Lepomis auritus (redbreast sunfish), L. gulosus (warmouth), L. punctatus (spotted sunfish), and Notropis cummingsae (dusky shiner). Results demonstrated a rapid decline in 137Cs within fish from Steel Creek during the 24-year period. For example, 137Cs concentrations in all fish species declined significantly among years, even after accounting for radioactive decay. The observed percent declines in 137Cs concentrations of individual species were 3-4 times greater between 1974 and 1981 compared to that expected by physical decay alone, and 2-3 times greater during 1981-1998. Ecological half-lives (EHLs) of 137Cs in fish ranged from 4.43 years in A. sayanus to 6.53 years in L. gulosus. The EHL for 137Cs in all fish species combined was 5.54 years. Current levels of 137Cs in fish from Steel Creek (1.16 Bq g(-1) dry wt. of whole body to below detection limits) indicate that the consumption of fish from this ecosystem poses little risk to humans and sensitive wildlife species. These results demonstrate the importance of incorporating the concept of ecological half-life into determinations concerning the length and severity of potential risks associated with radiocontaminants.

The spinal lax zone and neutral zone: measurement techniques and parameter comparisons.

The neutral zone (NZ) is a well-established parameter that describes the loose region of the spinal range of motion (ROM) where the spine moves easily with minimal applied force. The loose region is of interest clinically because in vitro studies show that with the onset of instability, this region increases before the ROM increases. The upper boundary of the NZ has been described as the displacement at which ligamentous resistance just begins. However, we hypothesized that a different parameter that we have named the lax zone (LZ) more accurately describes the region of ligamentous laxity. We hypothesized that the NZ is a smaller subset of the LZ that is governed by frictional properties at the joint. Methods for determining the spinal LZ experimentally are introduced. To demonstrate that the LZ is distinct from the NZ, both parameters were quantified in six normal cadaveric human C5-C6 specimens for three different preload magnitudes and three different preload directions. LZ variations with changing preload closely matched variations in the location of the load-deformation curve elbow, whereas NZ values followed specimen resting position instead, verifying parameter independence. Reproducibility and interspecimen variability values were approximately equivalent for both parameters. Compared in a separate data set, NZ and LZ were both more sensitive than ROM in response to cervical discectomy. With discectomy, the absolute change in LZ was larger and the percentage change in LZ was smaller than in NZ. The NZ may be a more appropriate measure when investigating the biomechanical effect of alterations to joint articulations and when the loading environment is well controlled. The LZ may be a more appropriate measure when investigating the effect of ligament/disc alterations and when the loading environment cannot be controlled. Future work is needed to compare the sensitivities of the LZ and NZ in detecting spinal instability onset for various injuries.

Three-dimensional head axis of rotation during tracking movements. A tool for assessing neck neuromechanical function.

The purpose of this article is to report normal variation in the screw (helical) axis of rotation of the head during various types of natural tracking movements. Nine normal subjects and eighteen subjects with neck injury faced a grid of targets separated by 10-degree intervals, and were instructed to use a head pointer (laser) to track whatever target was lit. Various horizontal, vertical, and oblique target sequences were employed. The normal subjects exhibited several consistent trends in finite screw axis parameter variation: vertical movements have a laterally-directed axis whose midsagittal plane crossing position is a function of the head orientation (typical range C3-T1); oblique movements have a diagonally-directed axis and an even greater orientation-specific range (C1-T1); and horizontal movements have a vertical axis that is modified near horizontal orientation extremes and is asymmetrically influenced by upward and downward bias orientations. Subjects with neck injury were seen to exhibit a variety of abnormal screw axis patterns.

Three-dimensional head kinematics and clinical outcome of patients with neck injury treated with spinal manipulative therapy: a pilot study.

OBJECTIVE: Finite helical axis parameters (FHAP) of the cervical spine and clinical measures were obtained to evaluate neck function and the clinical effects of spinal manipulative therapy in patients with "whiplash" (WL) type neck injury. DESIGN: Descriptive case series, 1 yr follow-up. SETTING: Three private chiropractic practices. SUBJECTS: Ten consecutive new patients with a history of neck injury, nine asymptomatic, volunteer controls. INTERVENTIONS: A 6-wk regimen of short lever manually assisted adjustments with an Activator Instrument, while acute, four patients received interferential electrotherapy. MAIN OUTCOME MEASURES: Cervical FHAP during normal movements, neck pain (visual analogue scale), active cervical range of motion and follow-up questionnaire. RESULTS: Based on six patients, the FHAPs appeared to mirror the clinical condition, being markedly deviant from the patterns observed in the control group for at least one or more of the tracking tasks for all but one of the patients. Mean pain scores decreased from 44.1 to 10.5 (t = 4.93; p < .0001) and mean total range of motion increased from 234 to 297 degrees (t = 5.68; p < .0001). At 1 yr, seven respondents noted stability of their symptoms at or near the level reported immediately after the 6-wk treatment period. CONCLUSIONS: Based on these preliminary data: a) FHAPs may aid in diagnosing and monitoring treatment of neck dysfunction, b) spinal manipulative therapy may be beneficial to some patients with neck injury and future study is warranted as a means to promote recovery of patients with neck injuries.