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Myelotoxicity parameters were monitored in female B6C3F1 mice exposed to 0, 1, 5, and 10% of a chemical mixture stock in drinking water for 2.5 to 31.5 weeks. The mixture consisted of 25 groundwater contaminants frequently found near toxic waste dumps, as determined by U.S. Environmental Protection Agency (EPA) surveys. Water consumption, body and organ weights, and hematological and histopathological examinations were conducted. No animals developed overt signs of toxicity after 2.5 weeks of treatment. No significant effect on bone marrow cellularity was observed after 2.5, 15.5, or 31.5 weeks of exposure; however, mice exposed to 5% or higher concentrations of the chemical mixture stock solution for 15.5 weeks showed significant suppression of granulocyte-macrophage progenitor cells (CFU-GM) and erythroid precursors (CFU-E) with no changes in body weight, histopathological or hematological parameters. Decreases occurred in erythrocyte mean corpuscular volume of mice exposed to a 10% solution for 15.5 weeks and to 5 and 10% solutions following 31.5 weeks of treatment. In addition, dose-related decreases were found in body, liver, and thymus weights in the 5 and 10% solutions exposure groups after 31.5 weeks. These results suggest that bone marrow may be a sensitive indicator for long-term, low-level exposure of multiple chemicals in mice. Furthermore, long-term exposure to highly contaminated groundwater may present a subtle risk to the hematopoietic system.
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For 3 months experimental dogs were exposed to +Gz acceleration applied 3 times a day for 3 days a week. The initial acceleration value was 8-9 G, then the parameter varied, depending on the tolerance limit which was evaluated with respect to heart rate disorders. Biochemical measurements showed the largest changes (decrease in total protein, increase in sugar, bilirubin, cholesterol, alkaline phosphatase and transaminases) after the first day of the repeated exposure to +Gz. Following 1-3 months of the exposure, the changes decreased significantly; however, the K+ concentration continued to decline and that of alkaline phosphatase continued to increase. The results obtained indicate the development of adaptation to repeated +Gz exposures which differs from that to short-term exposures.
Repeated cold-air exposures increase human triiodothyronine (T3) plasma clearance rates. To study the response of the nuclear T3 receptor (NT3R) in this condition, binding characteristics were analyzed in human mononuclear leukocytes (MNL). In addition, we supplemented one group of individuals with a daily oral replacement dose of T3 to isolate the influence of serum thyroxine (T4) and thyrotropin (TSH) levels on receptor kinetics. The subjects were exposed to cold air (4 degrees C) twice/d, 30 min/exposure, for a total of 80 exposures. The T3-subjects received placebo [n = 8] and the T3 + subjects received T3 (30 micrograms/d) [n = 8] in a double-blind fashion. Mononuclear leukocytes were isolated from peripheral blood before the cold exposure and drug regimen began, and then after every 20 exposures. The dissociation constant (Kd) and maximum binding capacity (MBC) of the NT3R values were log transformed to minimize between-subject variability. In the T3+ group, serum total thyroxine (TT4), free T4 (FT4), and TSH were approx 50% lower than both basal and T3-values. The log10Kd increased 0.304 +/- 0.139 (p < 0.04) and the log10MBC increased 0.49 +/- 0.10 (p < 0.001) in the T3+ subjects compared to baseline. This change in MBC represents a 311% increase in the MBC over baseline and a fivefold increase over placebo-treated subjects. The T3- group showed no change in MBC over the study. These results describe for the first time the rapid modulation of the NT3R in response to the combined influence of cold exposure and reduced circulating T4 and TSH.
This cross-sectional telephone survey study assessed prevalence rates of current chemical sensitivity, frequency of chemical odor intolerance, and self-reported Persian Gulf chemical exposures among 41 randomly sampled Department of Veterans Affairs outpatients who were Persian Gulf War (PGW) and PGW-era veterans. The participants were drawn from an initial random list of 100 veterans, of whom 28 PGW and 20 era veterans had correct telephone data on file. Of those contacted, 86% of PGW veterans (24/28) and 85% of era veterans (17/20) agreed to participate. Significantly more PGW veterans with poorer global health after military service reported considering themselves now "especially sensitive to certain chemicals" (86%, 12/14) than did the PGW veterans or era veterans in stable health (both comparison groups 30%, 3/10). Among PGW veterans, the subset with worse health associated with marked increases in chemical odor intolerance since their military service had a significantly higher odds ratio for exposure to multiple chemicals, notably wartime pesticides and insect repellent, than did comparison groups. The high rate of chemical sensitivity of PGW veterans with deteriorated health is almost three times that in PGW-era veterans and in elderly primary care outpatient veterans at the same Department of Veterans Affairs medical center and in community-based civilian samples (i.e., 30%). These preliminary findings suggest the need for further study of chemical sensitivity, including tests for acquired increases in neural sensitizability to multiple low-level chemicals, in ill PGW veterans.
Epidemiologic studies of the respiratory health effects of air pollution are intrinsically difficult because exposure is common, expected effects at concentrations found in developed countries are weak, random misclassification of exposure is common, and the respiratory health indicators have multiple etiologies. Exposures to air pollutants also are multidimensional, generally consisting of a mixture of gases and particles. In this paper, epidemiologic study designs are described, and their potential for evaluating effects of complex pollutant mixtures are discussed. Power to detect the independent effects of individual pollutants in a complex pollutant mixture or to measure their interactions is in general very weak unless the study is specifically designed to test such hypotheses. However, with innovative and creative design, the independent and joint effects of multiple pollutants should be estimable in epidemiologic studies.
BACKGROUND: Two cases of sudden unexpected deaths in patients with multiple sclerosis were investigated by the Office of The Chief Forensic Pathologist. METHOD: Case studies. RESULTS: Marked similarities of the deaths, including circumstances, scene examination, and autopsy findings including a complete drug screen were recorded. CONCLUSIONS: Exposure to high ambient temperature may pose a danger to patients with multiple sclerosis. Mechanisms of death and the potential dangers to patients with clinically widespread disease are discussed.
An increasing number of patients have been presenting with multiple symptoms they attribute to low-level chemical exposures, ie, multiple chemical sensitivities (MCS). Although some studies have evaluated such patients, the selection criteria has not been rigorously defined. The present study is the first to use a relatively rigorous definition of MCS to select patients for study. Comprehensive evaluation of medical, psychiatric, neuropsychological, and immunological status of a series of MCS patients is presented. In contrast to previous studies, patients in this study did not have a history of psychiatric disorder. However, some patients were currently depressed. Neuropsychological assessment did not reveal any abnormalities with the exception of one test of verbal memory for which performance was consistently poor relative to the normative sample. No significant immunological abnormalities were noted.
The individually different effects of exposure to comparable levels of chemicals might be partly explained by dissimilar response sensitivity towards chemicals. Multiple chemical sensitivity (MCS) might be the clinical endpoint of this altered sensitivity. Concerning a subclinical range of chemical sensitivity, 'challenge studies' with people reporting chemical sensitivity are needed to improve the knowledge about such differences. The chemical and general environmental sensitivity questionnaire (CGES) is a standardized screening tool for the selection of this group. In the present study 24 healthy male volunteers, half of them classified as sMCS-subjects, were experimentally exposed to 2-butanone and ethyl benzene at different levels (TLV-level vs. odor threshold). The strength of self-reported sensory irritations (nasal and ocular) and symptoms of bad smell were assessed, prior, during, and after the 4 hours of exposure. The time courses of sensory irritations were affected by sMCS. Across all exposure periods sMCS-subjects showed increasing symptom scores while control-subjects did not. Symptoms of bad smell were affected by three exposure-related factors (substance, level, duration) without any additional influence from the sMCS factor. Starting from these results it could be concluded that the time-depending influence of reported chemical sensitivity is most prominent for subjective data of sensory irritations.
BACKGROUND: Although many epidemiologic studies have investigated the association between exposure to secondhand smoke (SHS) and risk of coronary heart disease (CHD), few of these studies have assessed exposure measures from different sources over a lifetime. Therefore, we sought to test the association between lifetime cumulative exposure to SHS and risk of myocardial infarction (MI) (as an indication of CHD) among never smokers. METHODS: A population-based case-control study in which participants were 1541 never smokers (284 cases and 1257 controls) drawn from 1197 women and men with incident MI and 2850 healthy controls (aged 35-70 years) identified from 2 Western New York counties between 1995 and 2001. Study subjects were asked to report their exposure to SHS at home, at work, and in public settings from childhood to their present age. Exposure histories from each source were combined to form a cumulative lifetime exposure measure. Multiple logistic regression analysis estimated the association between SHS exposure and case status adjusted for age, sex, education, body mass index, race, drinking status, lifetime physical activity, hypertension, diabetes mellitus, and hypercholesterolemia. RESULTS: After adjustment for covariates, exposure to SHS was not significantly associated with an increased risk of MI. Compared with participants in the bottom tertile of SHS exposure, those in the top tertile had an odds ratio of 1.19 [95% confidence interval, 0.78-1.82] for MI. Virtually all subjects reported some exposure to SHS over their lifetime, but self-reported exposures declined over time, especially in the period closest to the interview. CONCLUSIONS: Exposure to SHS has declined sharply among nonsmokers in recent years. In the absence of high levels of recent exposure to SHS, cumulative lifetime exposure to SHS may not be as important a risk factor for MI as previously thought.
The influence of an extremely low frequency (ELF) electric field stimulus (30 Hz at 6 microV/cm rms), known to promote bone formation in vivo, was evaluated for its ability to affect bone cell function in vitro. To accomplish this, we developed an apparatus for the exposure of monolayer cell systems to electric fields in a manner that provides relatively uniform electric field exposure of multiple cell samples as well as a rigorous sham exposure. We show that field exposure significantly limits the normal increase in osteoblastic cell number and enhances alkaline phosphatase activity compared to sham-exposed samples. Moreover, these alterations are shown to occur in a cell density-dependent manner. Samples plated at 6 x 10(3) cells/cm2 show no effect of field exposure. In samples plated at 30 x 10(3) cells/cm2, 72 h of field exposure resulted in 25% fewer cells in the exposed samples, and a doubling of alkaline phosphatase activity in those cells compared to sham exposure. Experiments using a 12 h exposure to preclude significant changes in cell number during the exposure show this density-dependent response to be biphasic. Sparse cultures (< 50 x 10(3) cells/cm2) were not found to be affected by the field exposure, but increases in alkaline phosphatase activity occurred in cultures at densities of 50-200 x 10(3) and 200-350 x 10(3) cells/cm2 and no effect on alkaline phosphatase activity was seen in confluent cell cultures of greater than 350 x 10(3) cells/cm2.(ABSTRACT TRUNCATED AT 250 WORDS)
OBJECTIVE: The aim of this nested case-control study was to test the hypothesis that exposure to electromagnetic fields from high-voltage power lines increases the incidence of hematological cancers in adults. Data from an occupational exposure matrix was also used. METHODS: The study population comprised subjects aged 16 and above who had lived in a residence situated in a broad corridor around a high-voltage power line in 1980, or one of the years from 1986 to 1996. The cases were incident cases diagnosed 1980-1996. Two controls were matched to each case by year of birth, sex, municipality and first year entering the cohort. Time-weighted average exposure to residential magnetic fields generated by the power lines was calculated for the exposure follow-up from January 1, 1967 until diagnosis using cut-off points at 0.05 and 0.20 microT. In addition, job titles and industrial branch was classified as categories of hours per week in a magnetic field above background (0.1 microT). Subjects exposures were cumulated over occupationally active years for the exposure follow-up January 1, 1955 until diagnosis. RESULTS: When residential magnetic fields are evaluated, the two upper residential time weighted average magnetic field categories showed non-significant elevated odds ratios (ORs) for all leukemia combined (OR: 1.3, 95% confidence interval (CI) 0.7-2.5 and OR: 1.5, 95% CI: 0.8-3.0). The increased risk was confined to chronic lymphocytic leukemia, acute lymphocytic and acute myeloid leukemia. Lymphoma showed a non-significant lower OR in the upper exposure category. Multiple myeloma showed non-significant elevated ORs. Occupational exposure showed no significant association to exposure for any site. CONCLUSIONS: Some elevated ORs were observed in the present study, but the results are based on small numbers and no firm conclusions can be drawn.
The possible carcinogenicity of cobalt, iron, lead, manganese, mercury, platinum, selenium, and titanium is reviewed, taking into account epidemiological data, the results of animal experimental studies, data on mutagenic effects and on other in vitro test systems. Of the great variety of occupations where exposure to one of these metals may occur, only haematite mining has been clearly shown to involve an increased human cancer risk. While the possibility that haematite might in some way act as a carcinogen has to be taken into consideration it is more likely that other carcinogens are responsible. Certain platinum coordination complexes are used in cancer chemotherapy, are mutagenic, and likely to be carcinogenic. Cobalt, its oxide and sulfide, certain lead salts, one organomanganese, and one organotitanium compound have been shown to have a limited carcinogenic effect in experimental animal studies, and except for titanium appear to be mutagenic. Certain mercury compounds are mutagenic but none have been shown to be carcinogenic. The presently available data are inadequate to assess the possible carcinogenicity of selenium compounds, but a few observations suggest that selenium may suppress the effect of other carcinogens administered to experimental animals and may even be associated with lower cancer mortality rates in man. Epidemiological observations are essential for the assessment of a human cancer risk, but the difficulty in collecting past exposure data in occupational groups and the complexity of multiple occupational exposures with changes over time, limits the usefulness of retrospective epidemiological studies.
At the end of December 1993 and also at the end of January 1995, the river Meuse, one of the major rivers in Europe, flooded and river banks were inundated. We investigated the possible health risks of exposure to heavy metal concentrations in river bank soils resulting from the flooding of the river Meuse at the end of 1993. Soil and deposit samples and corresponding aerable and fodder crops were collected and analyzed for heavy metals. Although the soils of the floodplain of the river Meuse appeared severely polluted mainly by Cd and Zn, the heavy metal concentrations in the crops grown on these soils were within background ranges. Incidentally, the legal standard for Cd as endorsed by the Commodities Act was exceeded in wheat crops. The main exposure pathways for the general population were through the consumption of food crops grown on the river banks and through the direct ingestion of contaminated soils. For estimating potential human exposure in relation to soil pollution, we used a multiple pathway exposure model. For estimating the actual risk, we determined metal contents of vegetables grown in six experimental gardens. From this study, it can be concluded that there is a potential health risk for the river bank inhabitants as a consequence of Pb and Cd contaminations of the floodplain soils of the river Meuse, which are frequently inundated (averaged flooding frequency once every 2 years).
BACKGROUND: The medical literature has described the prevalence of latex allergy in the spina bifida population and its implications for surgical intervention. We report three cases of severe and unexpected intra-operative anaphylaxis secondary to latex exposure in non-spina bifida patients. METHODS: A retrospective review of case notes identified three non-spina bifida patients who suffered intra-operative anaphylaxis due to latex allergy. Personal and telephone interview and patient chart review was performed to detail a past history of multiple latex exposure, atopy, the anaphylaxis event and the postoperative outcome. RESULTS: Three non-spina bifida patients are described. One suffered a cardiopulmonary arrest, the remaining two patients had severe vascular hypotension and airway resistance that was only relieved after administration of vasoconstrictors and bronchodilators. Postoperatively, all three tested strongly positive to latex allergen testing. Each patient had a history of multiple surgical latex exposure and specific allergies or allergic-type symptoms pre-operatively. CONCLUSION: We believe that the predictors of a severe allergic reaction to latex with surgical exposure in non-spina bifida patients may be similar to those predictors known in the spina bifida population. Identification of such at-risk patients will reduce the risk of significant intra-operative morbidity and possible mortality by the introduction of a latex-free operating environment.
BACKGROUND: The alcohol deprivation effect (ADE) is a temporary increase in the voluntary intake of ethanol solutions following a period of alcohol deprivation. Multiple deprivations can prolong the expression of an ADE. This study examined the effects of initial deprivation length, concurrent exposure to multiple ethanol concentrations, and number of deprivation exposures on the magnitude and duration of the ADE in alcohol-preferring (P) rats. METHODS: Adult female P rats received 24-hr free-choice access to 10, 20, and 30% ethanol and water for 6 weeks. Rats were then randomly assigned to three groups; one group served as a nondeprived control, whereas the other two groups were initially deprived of ethanol for 2 or 8 weeks. The ethanol solutions were restored to both deprived groups for 2 weeks before the groups were deprived of ethanol for another 2 weeks. This cycle was repeated three times for a total of four deprivations. RESULTS: After the initial ethanol deprivation period, both deprived groups displayed a similar 2-fold increased ethanol intake (g/Kg/day) during the initial 24-hr period when ethanol was restored. Both deprived groups showed greater than 2-fold increases in intake of the 20 and 30% ethanol solutions after re-exposure. Ethanol consumption returned to baseline levels within 2 weeks, before the subsequent deprivation period. Multiple deprivations increased the magnitude of the ADE over that observed in the first deprivation during the initial 24-hr period of re-exposure and prolonged the duration of the ADE. In addition, repeated deprivations increased ethanol intake in the first 2-hr period of re-exposure and produced blood ethanol levels in excess of 150 mg/100 ml. CONCLUSIONS: Alterations in the reinforcing and/or aversive effects of alcohol occurred after a single prolonged deprivation and were enhanced with repeated deprivations.
Epidemiologically, disasters represent multiple forms of possible exposures, including exposure type (eg, natural versus human-made), intensity, and duration. It has been suggested that the consequences of human-made disasters (eg, terrorist incidents) may be more severe than those of natural disasters; recent evidence suggests that there may be a high prevalence of posttraumatic stress disorder (PTSD) among both direct survivors of such attacks and in the general population. Several studies after the September 11, 2001, terrorist attacks found that the prevalence of PTSD was higher in New York City than it was in the rest of the US and that there was a substantial burden of PTSD among persons who were not directly affected by the attacks. This raises important questions about the meaning of "exposure" to a disaster. Using data from an assessment of PTSD in the first 6 months after September 11th we considered the nature of the PTSD experienced by persons who were not directly affected by the September 11th attacks. These data suggest that persons in the general population may have clinically important posttraumatic stress symptomatology after a mass terrorist incident. Future research should consider mechanisms through which persons in the general population may be at risk for PTSD after such incidents.