Unprocessed Atmospheric Nitrate in Waters of the Northern Forest Region in the U.S. and Canada

Little is known about the regional extent and variability of nitrate from atmospheric deposition that is transported to streams without biological processing in forests. We measured water chemistry and isotopic tracers (δ¹⁸O and δ¹⁵N) of nitrate sources across the Northern Forest Region of the U.S. and Canada and reanalyzed data from other studies to determine when, where, and how unprocessed atmospheric nitrate was transported in catchments. These inputs were more widespread and numerous than commonly recognized, but with high spatial and temporal variability. Only 6 of 32 streams had high fractions (>20%) of unprocessed atmospheric nitrate during baseflow. Seventeen had high fractions during stormflow or snowmelt, which corresponded to large fractions in near-surface soil waters or groundwaters, but not deep groundwater. The remaining 10 streams occasionally had some (<20%) unprocessed atmospheric nitrate during stormflow or baseflow. Large, sporadic events may continue to be cryptic due to atmospheric deposition variation among storms and a near complete lack of monitoring for these events. A general lack of observance may bias perceptions of occurrence; sustained monitoring of chronic nitrogen pollution effects on forests with nitrate source apportionments may offer insights needed to advance the science as well as assess regulatory and management schemes.

The Influence of Marcellus Shale Extraction Emissions on Regionally Monitored Dry Reactive Nitrogen Deposition

Emissions of nitrogen oxides (NO_x) in the United States (U.S.) from large stationary sources, such as electric generating units, have decreased since 1995, driving decreases in nitrogen deposition. However, increasing NO_x emissions from emerging industries, such as unconventional natural gas (UNG) extraction, could offset stationary source emission reductions in shale gas producing regions of the U.S. The Marcellus Shale in the northeastern U.S. has seen dramatic increases in the number of wells and associated natural gas production during the past 10 years. In this study, we examine the potential impacts of shale gas development on regional NO_x emission inventories and dry deposition fluxes to Clean Air Status and Trends (CASTNET) sites in Pennsylvania and New York. Our results demonstrate that the current distribution of CASTNET sites is ineffective for monitoring the influence of Marcellus well NO_x emissions on regional nitrogen deposition. Despite the fact that existing CASTNET sites are not influenced by UNG extraction activity, NO_x emissions densities from shale gas extraction are substantial and are estimated to reach up to 21 kg NO_x ha^-1 year^-1 in some regions. If these emissions deposit locally, UNG extraction activity could contribute to critical nitrogen load exceedances in areas of high well density.

Assessment of tolerant sunfish populations (Lepomis sp.) inhabiting selenium-laden coal ash effluents. 1. Hematological and population level assessment

Sunfish were collected from coal ash effluent-receiving streams and Ohio River watershed reference sites to assess the effects of exposure to low-level selenium concentrations. Selenium, copper, and arsenic concentrations were statistically higher in tissue samples from exposed fish than in reference fish. Leukopenia, lymphocytosis, and neutropenia were evident in exposed fish and were indicative of metal exposure and effect. White blood cell counts and percent lymphocyte values were significantly correlated with liver selenium concentrations. Plasma protein levels were significantly lower in exposed fish than in fish from the Ohio River, indicating that exposed fish may have been nutritionally stressed. Condition factors for fish from the ash pond-receiving streams were the same as, or lower than, those of fish from the reference sites. There was no evidence that the growth rate of fish in the receiving streams differed from that of fish in the reference streams. Despite liver selenium concentrations which exceeded reported toxicity thresholds and evidence of significant hematological changes, there were no significant differences in fish condition factors, liver-somatic indices, or length-weight regressions related to selenium.

Recreational use of inhalant drugs by adolescents: a challenge for family physicians

BACKGROUND AND OBJECTIVES

This paper assesses the incidence and prevalence of inhalant use in an adolescent population. The purpose was to document patterns of incidence and prevalence.

METHODS

A survey study was conducted, in which self-reported measures of inhalant use were assessed during 3 consecutive years. All surveys were completed as part of a school-based study. The responses of 10,198 middle school and high school students were analyzed. The primary measures included self-reported use of substances that were inhaled to create a state of euphoria.

RESULTS

Of the responding students, overall rates of 12.8% for lifetime use and 4.6% for past-month use were observed. Cross-sectional analysis revealed increasing inhalant use among students in grades 6-8 that leveled off in grade 9 and decreased in grades 10-12. Incidence of inhalant use was found to be increasing in younger adolescents.

CONCLUSIONS

Inhalant use may be an early marker of substance abuse and should be the focus of increased prevention and early diagnosis and treatment. Family physicians may be among the first to suspect inhalant use in casual users and should be alert to inhalant use among adolescent patients.

The effect of spiroorthocarbonate volume modifier co-monomers on the in vitro toxicology of trial non-shrinking dental epoxy co-polymers

A major improvement in dental restoratives is possible through the development of biomaterials that do not shrink upon polymerization, hence, avoid leakage and subsequent breakdown. Polymers containing spiroorthocarbonates (SOCs) show promise in this respect, but their toxicology in copolymerized materials has not been explored. In this study, the in vitro toxicology of these materials in homopolymer form and in two trial non-shrinking epoxy co-polymers was evaluated for cytotoxicity and mutagenicity. Cytotoxicity was determined by the MTT test to measure the lethality effect on mouse L929 cells. Mutagenicity was evaluated using the Ames-Salmonella Test. For comparison, commercial composite and adhesive materials as well as several other materials of current interest in dentistry were also evaluated. Epoxy resin samples containing 5% of either T/T SOC or Dp SOC reduced the cytotoxicity (TC50) from approximately 400 to 800 micrograms/200 microliters. The epoxy-spiro copolymers had more favorable TC50 values than the commercial product Super-Bond. They showed TC50 values on the order of 35% greater than Super-Bond and 45% less than Scotchbond 2, the latter two being materials currently used in the clinic. These two comparatives demonstrated dose response curves with lower doses at maximum cell kill values than the spiro materials. The epoxy formulations all showed weak mutagenesis, but this is attributed to the epoxy formulation and not the SOCs. Although considerable toxicology is yet be conducted, these in vitro results suggest that biocompatible copolymer formulations for spiroorthocarbonates are a developmental reality.

Cerebral infarction verified by cranial computed tomography and prognosis for survival following transient ischemic attack

Of 564 consecutive patients with transient ischemic attack, 350 (62%) had cranial computed tomography performed. Except for date of admission and smoking history, there were few differences between the patients evaluated with computed tomography and the 214 who were not. Cerebral infarcts were found in 59 (17%) of the 350 tomographic evaluations. Previous clinically diagnosed stroke, older age, and male sex were all significantly associated with the occurrence of tomographically verified infarcts (p less than 0.05). After controlling for stroke history and other important covariates, patients with tomographically verified infarcts had significantly shorter survival times than did patients without evidence of infarction on computed tomography (p = 0.035). Thus, cranial computed tomography findings appear to have important prognostic value for estimating survival following transient ischemic attack.

Characteristics of stroke victims associated with early cardiovascular mortality in their children

We assessed the relationship between characteristics of stroke victims and the risk of early death from coronary or cerebrovascular disease (CCVD) among their children. For each of 55 stroke patients selected from a registry which enrolled patients between 1969 and 1973, an index of their progeny's survival was calculated using the age in 1987 of 197 surviving children, and the age at and cause of death for 55 deceased children. Increased risk of CCVD death within families was significantly related to parental age at the time of first stroke, and with the parental history of diabetes mellitus. No significant relationship was found between the children's risk of CCVD death and the stroke patient/parent's sex, race, history of hypertension or cardiac disease, stroke diagnosis (infarction vs hemorrhage), or severity upon admission. These results suggest that family histories of cerebrovascular disease may impart differential risks, depending upon a family history of diabetes, and perhaps, the ages at which ancestral strokes first occurred.

Changes in survival after transient ischemic attacks: observations comparing the 1970s and 1980s

We compared survival following transient ischemic attack (TIA) in 2 prospective cohorts of TIA patients admitted to Wake Forest University Medical Center. The 1st consisted of 177 patients admitted between 1961 and 1973, and the 2nd of 185 patients admitted between 1980 and 1983. Patients in the 2nd cohort had significantly greater longevity than patients in the 1st cohort, both univariately and after adjustment for cerebrovascular risk factors. The adjusted 1-year survival estimate increased from 91% in the 1st cohort to 98% in the 2nd, and the adjusted 3-year survival estimate increased from 83% in the 1st to 94% in the 2nd. The underlying causes for this dramatic improvement in survival may include early identification and aggressive management of TIAs or coexisting diseases, improved management of subsequent completed strokes or myocardial infarctions, or unadjusted differences in these cohorts. The data imply that reports of TIA survival from different periods may not be comparable.

Cerebral infarction in patients with transient ischemic attacks

Cranial computed tomography of 284 patients with transient ischemic attacks (TIAs) and without previous stroke was evaluated. The sample population included patients with carotid and/or vertebrobasilar TIAs. Computed tomography revealed cerebral infarction in 34 patients, including 5 with multiple infarctions. The lesion location was consistent with TIA symptoms in 16 patients. In another 16 patients, however, the lesion location did not correspond to the TIA symptoms; these lesions were attributed to previous silent infarctions. Two patients with multiple infarctions had both symptomatic and asymptomatic lesions. Age and carotid stenosis were each significantly related to an increased chance of detecting cerebral infarction (either symptomatic or asymptomatic). No significant relationship between race, gender, hypertension, diabetes, cardiac disease, or smoking and the incidence of infarction was found by either univariate or multivariate analyses.