Blink reflex latency after exposure to trichloroethylene in well water

Lack of Trigeminal Nerve Toxicity in Rats Exposed to Trichloroethylene Vapor for 13 Weeks

Male and female Fischer-344 rats were exposed to 1,1,2-trichloroethylene (TCE) at 250, 800, or 2500 ppm for 6 h/day, 5 days/week, for 13 weeks. Weekly body weights and daily clinical observations were recorded and a functional observational battery (FOB) was performed monthly. Postexposure neurotoxicological evaluations included an electrodiagnostic evaluation of auditory function, the trigeminal nerve, and a comprehensive neuropathological examination. After 8 weeks of exposure, female, but not male, rats exposed to 2500 ppm were slightly more reactive to handling than the controls but not after 13 weeks of exposure. After 13 weeks, female rats exposed to 2500 ppm TCE were slightly more active during the 1-min observation period than the controls. There were no treatment-related differences in grip performance, landing foot splay, or on the trigeminal nerve–evoked potential at any dose. At 2500 ppm TCE, mild frequency-specific hearing deficits were observed, including elevated tone-pip auditory brainstem response thresholds. Focal loss of hair cells in the upper basal turn of the cochlea was observed in 2500 ppm–exposed rats. Except for the cochleas of 2500 ppm–exposed rats, no treatment-related lesions were noted during the neuro-histopathologic examination. The no-observable-adverse-effect level for this study was 800 ppm based on ototoxicity at 2500 ppm.

Different behavioral effect dose-response profiles in mice exposed to two-carbon chlorinated hydrocarbons: influence of structural and physical properties

The present study aimed to clarify whether dose-response profiles of acute behavioral effects of 1,2-dichloroethane (DCE), 1,1,1-trichloroethane (TCE), trichloroethylene (TRIC), and tetrachloroethylene (PERC) differ. A test battery involving 6 behavioral endpoints was applied to evaluate the effects of DCE, TCE, TRIC, and PERC in male ICR strain mice under the same experimental conditions. The behavioral effect dose-response profiles of these compounds differed. Regression analysis was used to evaluate the relationship between the dose-response profiles and structural and physical properties of the compounds. Dose-response profile differences correlated significantly with differences in specific structural and physical properties. These results suggest that differences in specific structural and physical properties of DCE, TCE, TRIC, and PERC are responsible for differences in behavioral effects that lead to a variety of dose-response profiles.

Toxic neuropathies associated with pharmaceutic and industrial agents

Neuropathies associated with industrial, environmental, and pharmacologic toxicants are uncommon. Nevertheless, it is important to consider toxic etiologies in the differential diagnosis of neuropathies, because they are among the most treatable forms of peripheral nervous system dysfunction. The purpose of this article is to discuss the clinical investigation of a suspected toxic neuropathy, to review some of the more common or representative neurotoxicants, and to identify the methods for establishing causation.

Crises temporales symptomatiques d’une intoxication au trichloroéthylène

INTRODUCTION

Trichloroethylene (TCE) is extensively used as a degreasing agent in the metal industry and as a solvent for organic compounds. Its neurotoxicity (with respect to both the peripheral and central nervous systems) is now widely acknowledged.

OBSERVATION

Here, we report the case of a 32-year-old male drug addict presenting temporal seizures after "huffing" TCE (i.e. voluntary inhalation). The patient also deve loped a "psycho-organic syndrome" which included cognitive dysfunction (with memory disorders in particular) and personality changes. These disorders had not been noticed by the patient's wife prior to the last episode of inhalation. Four months later, the cognitive disorders had stabilized and no further seizures had been observed.

CONCLUSION

The patient's overall clinical picture (notably featuring neuropsychological disorders) and electroencephalographic and brain imaging data argue in favor of a selective effect of TCE on the temporal lobe.

Do duration of exposure, proximity to electronic manufacturing plants, and involvement in a lawsuit affect chlorinated solvent toxicity?

The author examined the effects of duration of residence, proximity to microchip plants, and being a party in litigation involving neurobehavioral functioning in individuals who had been chronically exposed to trichloroethylene-associated solvents from the environment. The author compared duration of exposure for the 236 residents, all of whom were located in 3 proximity zones in Phoenix, Arizona; some of the individuals had been in the process of solvent-related litigation for fewer than 10 yr, whereas some had been involved for more than 10 yr. The 236 residents were compared with 58 nonclaimants in 3 residential areas within the exposure zones. Neurobehavioral function testing was described in the study that appears prior to this study in this issue. Prior to comparisons, test scores were adjusted for age, sex, education level, and other significant factors. Individuals who had been exposed for fewer than 10 yr were not different from individuals who had been exposed for longer periods. Proximity to microchip plants produced no statistically significant effects. Among the 169 exposed subjects (i.e., exposure for 15 yr to trichloroethylene-associated solvents), of whom some were parties in lawsuits, those who lived in the near west area (Zone A) of Phoenix did not differ with respect to results of the 14 neurobehavioral tests that were administered. However, Zone B subjects, located to the north of the plant, differed with respect to 2 of the tests; and Zone C subjects, located beyond Zone A, Phoenix, differed with respect to 3 of the tests. In conclusion, duration of residence, proximity to microchip plants, and being a party to a lawsuit had no significant effects on neurobehavioral functioning, but, in this study, parties in the lawsuit were subjects who experienced more frequent symptoms.

Is neurotoxicity associated with environmental trichloroethylene (TCE)?

Individuals who lived near 2 electronic manufacturing plants were exposed to odorous chlorinated solvents by inhalation (directly) and by out gassing from well water. An exposure zone was defined by concentrations of trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, and vinyl chloride in groundwater. The author adopted trichloroethylene as a "shorthand" for the exposure designation. Residents complained of impaired recall and concentration, and of dizziness; therefore, the focus of this investigation was brain functions. Neurobehavioral functions, Profile of Mood States, frequencies of 35 symptoms, and questionnaire responses provided by 236 residents from exposure zones were compared with responses provided by 161 unexposed regional referents and by 67 Phoenix residents who lived outside the exposure zone areas. Pulmonary functions were measured with spirometry. Residents of the exposure zones were compared with regional referents, and the former had significantly (p < .05) delayed simple and choice reaction times, impaired balance, delayed blink reflex latency R-1, and abnormal color discrimination. In addition, these individuals had impaired (1) cognitive functions, (2) attention and perceptual motor speed, and (3) recall. Individuals who lived in exposure zones had airway obstructions. Adverse mood state scores and frequencies of 33 of 35 symptoms were elevated. In conclusion, individuals who lived in the exposure zones had neurobehavioral impairments, reduced pulmonary functions, elevated Profile of Mood State scores, and excessive symptom frequencies.

Toxicity of trichloroethylene following inhalation and drinking contaminated water

The neurobehavioural effects of trichloroethylene (TCE) were studied in rats following administration of the solvent orally (350, 700 and 1400 ppm in drinking water for 90 days) and through inhalation (376 ppm for 4 h a day, 5 days per week for 180 days). Various aspects of spontaneous locomotor activity were assessed at different periods after exposure through either of the routes. Oral exposure to TCE had no significant effect on spontaneous locomotor activity or cognitive ability, whereas inhalation to the solvent resulted in an increase in the distance travelled and horizontal activity counts at day 30 but a decrease at day 60 of exposure. The time spent in ambulatory and stereotypic movements as well as the number of stereotypic movements were enhanced significantly only at day 30. The resting time was decreased at day 30 but enhanced at day 60 of exposure. The learning ability was not affected significantly up to day 180. The results highlight the neurotoxic potential of inhalation exposure to TCE.

Evaluation of blink reflex results obtained from workers previously diagnosed with solvent-induced toxic encephalopathy

We reviewed blink reflexes recorded from 51 railroad workers with long-term occupational exposure to solvents who were diagnosed by others with solvent-induced toxic encephalopathy. No worker fulfilled conventional clinical criteria for dementia or trigeminal mononeuropathy. All workers had normal R1 and R2 blink reflex latencies. R1 latencies correlated significantly with several nerve conduction measures, including F wave latencies, suggesting that some intersubject variability reflected intrinsic conduction properties, not isolated brain-stem function. Although normal, the workers' R1 latencies were significantly prolonged compared with historical control groups, including gender-matched control subjects of similar mean age (11.2 ms vs 9.9 ms; P < 0.0001). Stepwise multiple regression models demonstrated significant associations of R1 latency with age and use of CNS-active prescription medications (P = 0.003), but duration of occupational solvent exposure did not enter into the models. Paradoxically, workers using CNS-active medications had significantly shorter R1 latencies compared with workers not using such medications (10.9 vs 11.7 ms; P = 0.01). Job title, another potential surrogate measure of exposure, was not significantly related to reflex latencies. The geographical site of predominant solvent exposure did influence R1 latency, and workers from one site had longer exposure duration and longer R1 latencies than remaining workers. However, an interaction between age and exposure duration (r = 0.39; P = 0.003) confounded interpretation of this observation. Disability or work status, mental status findings, or classification of encephalopathy did not influence blink reflex latencies. The overall results do not support, but do not entirely exclude, a possible relationship between subclinical blink reflex abnormalities and occupational exposure to solvents. Nevertheless, it is clear from these results that the small group differences in R1 latency between exposed workers and control subjects are of no diagnostic importance and of uncertain physiologic importance, and they may reflect unrecognized confounders and technical factors.

Effects of diesel exhaust on neurobehavioral and pulmonary functions

Ten railroad workers and 6 electricians referred for shortness of breath also had slowness of response, memory loss, and disordered sleep, all of which suggested neurobehavioral impairment. The hypothesis was that diesel exhaust causes central nervous system impairment. Six electricians worked within enclosed concrete walls and roofs that trapped diesel exhaust from trucks. Seven railroad mechanics had tuned diesel engines indoors for 15-50 y, and 3 crewmen rode in locomotives. Neurobehavioral and visual functions were measured with a 26-test battery. Compared with unexposed men, the 16 in this study had significantly impaired reaction time, balance, blink reflex latency R-1, Culture Fair, peg placement, trail making, and verbal recall. Thirteen men had abnormal visual fields, and 11 had abnormal color confusion indices. Nine men had airways obstruction. The author could not attribute abnormalities to confounding factors or bias. Severe neurobehavioral impairment was associated with exposure to confined diesel exhaust. In additional studies of diesel-exposed workers, especially drivers of locomotives and trucks, investigators should use sensitive neurobehavioral methods.

Agency for Toxic Substances and Disease Registry's 1997 priority list of hazardous substances. Latent effects--carcinogenesis, neurotoxicology, and developmental deficits in humans and animals

In support of Superfund re-authorization legislation, the Division of Toxicology of the Agency for Toxic Substances and Disease Registry (ATSDR) prepared a chemical-specific consultation document for Congress that identified those chemicals with carcinogenic, neurological, or developmental adverse effects having a latency period longer than 6 years. The review was limited to the top 50 substances listed on ATSDR's 1997 Priority List of Hazardous Substances (Priority List). Among the top 50 chemicals, a review of the technical literature indicated that 38 (76%) were classified as "reasonably anticipated," "possibly," or "probably" capable of causing cancer in humans, based either on human and animal data. Eight chemicals (16%) had well-established cancer latency periods in humans of 6 years or more following exposure. Three substances (6%)--arsenic, creosote, and benzidine--had data indicating latency periods longer than 6 years. The technical literature review likewise confirmed the potential for neurological and developmental effects with a latency of 6 years. Twenty-seven (54%) of the top 50 substances caused acute and/or chronic neurotoxic effects; a number of these also caused neurological effects that persisted beyond 6 years (or the equivalent in animal studies) such as: behavioral problems, neurological deficiencies, reduced psychomotor development, cognitive deficiencies, and reduced IQ. Twenty-eight substances (56%) caused adverse developmental effects in offspring of exposed individuals or animals including increased fetal and infant mortality, decreased birth weights and litter sizes, and growth delays. Latency periods for related chemicals are expected to be similar due to structural and toxicological similarities.

Neurotoxicity from airborne chemicals around a superfund site

A pilot investigation had shown that 88 people living within 2.4 km of a waste chemical disposal and oil-reprocessing facility which operated from 1966 to 1983 had reduced neurobehavioral performance compared to 66 regional referents. A geographic model of dispersal predicted less effect with greater distance from the distilling. To explore this gradient and the boundaries of the adverse effects, we tested 408 residents in random proportional samples of concentric zones from the center out to 4.8 km that were divided by compass octants. Reaction times, balance, blink reflex latency, color discrimination, Culture Fair, pegboard, and Trail Making A and B were measured. Patients completed a Profile of Mood States, frequency of 33 symptoms, and medical, occupational, and exposure histories. Distance and direction from the site and duration of residence were examined for effect on each test score by stepwise linear regression. Exposed subjects' had diminished reaction time, balance, color score, and scores for Culture Fair, pegboard, and Trail Making A and B compared to referents. Functional impairment was not correlated with distance or direction from the site but subjects with short durations of residence had better function on one test. Combinations of these factors were not predictive.

Approach to neurotoxicity tort cases

This article provides the neurologist with simple methods that can be applied to all clinical neurologic evaluations, regardless of the future potential for litigation. This article defines the appropriate application and interpretation of conventional neurologic, neurophysiologic, neuropsychological, and biochemical diagnostic tests that are sensitive to neurotoxic exposures. This article also provides the neurologist with guidance in the preparation of clinical findings and tips on the recognition and use of supportive literature that is often required for admissibility of evidence at a deposition or testimony.

Neurobehavioral and respiratory findings in jet engine repair workers: A comparison of exposed and unexposed volunteers

Workers repairing jet engines had respiratory, rheumatic, and neurobehavioral symptoms. They had welded and ground stainless steel parts using hard metal tools and cleaned metal with chlorinated and fluorinated organic solvents. We compared 154 workers and 112 unexposed subjects, all volunteers of similar ages and with similar educational levels, for abnormalities on chest radiographs, spirometric measurements, and questionnaires. Also appraised were performance of reaction time, balance, blink reflex latency, color discrimination, Culture Fair, vocabulary, slotted pegboard, trail making A and B, profile of mood states (POMS), and frequencies of 35 symptoms. Compared to unexposed subjects, workers had significantly more respiratory symptoms but no differences in pulmonary function. They had significantly prolonged simple and choice reaction time (P<0.0001), and abnormal balance with eyes open and eyes closed (P<0. 0001), and abnormal color discrimination. Blink reflex latency was abnormal in both exposed workers and in local unexposed compared to other reference groups. Focus of the inquiry on lung disease helped ensure that for neurobehavioral tests confounding factors were minimal and known biases were small. We tentatively attribute the neurobehavioral impairments and increased symptom frequencies to chlorinated solvent exposure. Excessive respiratory symptoms are attributed to welding stainless steel combined with cigarette smoking. Specifically, manganese exposure may have affected the respiratory and the central nervous systems.

Neurobehavioral impairment and symptoms associated with aluminum remelting

The author's objective was to assess whether aluminum reclamation (recycling) exposure in a plant in the southeastern United States was associated with neurobehavioral and pulmonary impairment and symptoms. The author made cross-sectional comparisons of 41 workers to 32 local and 66 regional referents to assess whether aluminum recycling was associated with neurobehavioral and pulmonary impairment and symptoms. Methods included neurophysiological, psychological, and pulmonary-function tests; a Profile of Mood States (POMS); and questionnaires. The exposed subjects had slower simple and choice reaction times than referents (i.e., 77 milliseconds [ms] versus 137 ms, respectively [p < .0001]); balance in the exposed subjects, measured as sway speed (with eyes closed), was .32 cm/s faster than for referents (p < .005); and color discrimination was less acute in exposed subjects (p < .0001). In the exposed versus referent subjects, Culture Fair scores were lower by a factor of 8.3 (p < .0001), Trail Making A was 10 s longer (p < .001), Trail Making B was 50 s longer (p < .0001), peg placement required an additional 9 s (p < .008), and POMS scores were fourfold higher (p < .0001). These described differences were not explained by age, bias, or confounding factors. Workers had more neurobehavioral, rheumatic, and respiratory symptoms than did referents. The author attributed the differences between the two groups to chemical exposures from aluminum remelting, including aluminum, manganese, vinyl chloride monomer, and other chemicals. Workplace air could not be sampled, but because a problem was identified, levels of these, as well as other chemicals, should be measured in future studies.

Exposure to trihalomethanes and adverse pregnancy outcomes

Exposure during pregnancy to disinfection by-products in drinking water has been hypothesized to lead to several adverse reproductive outcomes. We performed a retrospective cohort study to examine the relation of trihalomethane exposure during the third trimester of pregnancy to low birthweight, term low birthweight, and preterm delivery. We matched Colorado birth certificates from January 1, 1990, through December 31, 1993, to historical water sample data with respect to time and location of maternal residence based on census block groups. After excluding births from all census block groups with no trihalomethane sample data and restricting to singleton white births with 28-42 weeks of completed gestation (>400 gm), we studied 1,893 livebirths within 28 census block groups. We found a weak association of trihalomethane exposure during the third trimester with low birthweight (odds ratio = 2.1 for the highest exposure level; 95% confidence interval = 1.0-4.8); a large increase in risk for term low birthweight at the highest level of exposure (odds ratio = 5.9; 95% confidence interval = 2.0-17.0); and no association between exposure and preterm delivery (odds ratio = 1.0 for the highest exposure level; 95% confidence interval = 0.3-2.8). The small number of adverse outcomes reduced the precision of risk estimates, but these data indicate a potentially important relation between third trimester exposure to trihalomethanes and retarded fetal growth.

Dichloroacetylene: effects on the rat trigeminal nerve somatosensory evoked potential

Humans overexposed to trichloroethylene (TCE), under specific conditions, were reported to develop trigeminal nerve dysfunction. A degradation byproduct dichloroacetylene (DCA), however, has been suggested as the probable neurotoxicant rather than TCE. Studies in mice, rats, and rabbits support the hypothesis of DCA-induced trigeminal neurotoxicity. This study, therefore, was conducted to characterize DCA-induced trigeminal nerve dysfunction in rats using the electrodiagnostic procedure trigeminal nerve-stimulated somatosensory evoked potential (TSEP). A group of six rats was exposed once to DCA (approximately 300 ppm) or room air for 2.25 h and a separate group of six rats was not exposed and served as controls. Trigeminal nerve somatosensory evoked potentials (TSEPs) were collected before exposure and 2, 4, and 7 days postexposure. Because DCA was manufactured from TCE with acetylene added as a stabilizer, another group of rats was exposed to TCE and acetylene without generation of DCA. TSEPs from DCA-exposed rats were smaller and slower compared to their baseline recordings and to the concurrent negative controls. TSEPs from the controls and the TCE/acetylene-exposed rats were unchanged. Neuropathology did not reveal treatment-related lesions. It was concluded that the rat is mildly to markedly susceptible to DCA-induced trigeminal nerve dysfunction as assessed by TSEP, but that the kidney was the likely target organ based on gross observations and the DCA literature.

Trichloroethylene--a review of the literature from a health effects perspective

This report reviews the literature on the impact of exposure to trichloroethylene (TCE) on human health. Special emphasis is given to the health effects reported in excess of national norms by participants in the TCE Subregistry of the Volatile Organic Compounds Registry of the National Exposure Registries--persons with documented exposure to TCE through drinking and use of contaminated water. The health effects reported in excess by some or all of the sex and age groups studied were speech and hearing impairments, effects of stroke, liver problems, anemia and other blood disorders, diabetes, kidney disease, urinary tract disorders, and skin rashes.

Neurotoxic effects from residential exposure to chemicals from an oil reprocessing facility and superfund site

Neurotoxicity has been described in workers exposed to solvents, PCBs, certain metals, and polyaromatic hydrocarbons but not often in residents near refineries or factories. We compared the neurobehavioral performance of residents near a plant that reprocessed used motor oil and chemical waste from 1966-1983 to referents from beyond the plant's modeled air dispersal and water drainage zones. Neurophysiological and psychological tests, a Profile of Mood States (POMS) and a symptom questionnaire were administered to 131 subjects exposed at the site who were matched for age, sex, and ethnicity 2:1 with 66 unexposed subjects from 35 km away. Test scores were adjusted for a 1.4-year difference in educational attainment by coefficients from regression equations but not for income as the latter coefficients were not significant. Exposed subjects were significantly impaired for body balance (sway speed) and simple and two choice visual reaction time as compared to referents. Blink reflex latency (R-1) and eye closure speed were normal in both groups. Cognitive function in the exposed was impaired as measured by Culture Fair and by block design from the WAIS. Placing pegs in a grooved board and making of trails (A and B) were also impaired. Group differences in recall and memory were not significant. The exposed group's symptom frequencies and POMS scores for depression, anger, confusion, tension, and fatigue were elevated indicating depression. Confounding from medical and neurological disorders or occupational exposures was minimal. Subjects exposed residentially for up to 17 years to chemicals dispersed from a waste oil reprocessing plant showed neurophysiological and neuropsychological impairment.

An epidemic in Cuba of optic neuropathy, sensorineural deafness, peripheral sensory neuropathy and dorsolateral myeloneuropathy

An epidemic outbreak of peripheral neuropathy affected Cuba in 1992-93 resulting in 50,862 cases (national cumulative incidence rate (CIR) 461.4 per 100,000). Clinical forms included retrobulbar optic neuropathy, sensory and dysautonomic peripheral neuropathy, dorsolateral myeloneuropathy, sensorineural deafness, dysphonia and dysphagia, spastic paraparesis, and mixed forms. For epidemiological purposes, cases were classified as optic forms (CIR 242.39) or peripheral forms (CIR 219.25). Increased risk was found among smokers (odds ratio (OR) 4.9), those with history of missing meals (OR 4.7) resulting in lower intake of animal protein, fat, and foods that contain B-vitamins, combined drinking and smoking (OR 3.5), weight loss (OR 2.8), excessive sugar consumption (OR 2.7) and heavy drinking (OR 2.3). Optic neuropathy was characterized by decreased vision, bilateral and symmetric central or cecocentral scotomata, and loss of color vision due to selective lesion of the maculopapillary bundles. Peripheral neuropathy was a distal axonopathy lesion affecting predominantly large myelinated axons. Deafness produced selective high frequency (4-8 kHz) hearing loss. Myelopathy lesions combined dorsal column deficits and pyramidal involvement of lower limbs with spastic bladder. Clinical features were those of Strachan syndrome and beriberi. Intensive search for neurotoxic agents, in particular organophosphorus esters, chronic cyanide, and trichloroethylene intoxication, yielded negative results. Treatment of patients with B-group vitamins and folate produced rewarding results. Most patients improved significantly and less than 0.1% of them remained with sequelae; there were no fatal cases. Supplementation of multivitamins to the entire Cuban population resulted in curbing of the epidemic. Overt malnutrition was not present, but a deficit of micronutrients, in particular thiamine, cobalamine, folate and sulfur amino acids appears to have been a primary determinant of this epidemic.

Assessment of urban population exposure to trichloroethylene and tetrachloroethylene by means of biological monitoring

Exposure of the general population to trichloroethylene and tetrachloroethylene under normal environmental conditions, achieved with biological monitoring, was assessed, and the possible influence of these compounds via drinking water on the body burden was revealed. A total of 79 subjects with no known solvent exposure was selected, by stratified sampling, from the residents of the city of Zagreb. Trichloroethylene and tetrachloroethylene were determined in blood, and trichloroethanol and trichloroacetic acid were determined in plasma and urine. Drinking water samples were also analyzed for trichloroethylene and tetrachloroethylene. Concentrations of trichloroethylene and tetrachloroethylene in blood, trichloroacetic acid in plasma, trichloroacetic acid in urine, trichloroethylene in drinking water, and tetrachloroethylene in drinking water were as follows: < 0.015 to 0.090 micrograms/l, < 0.010 to 0.239 micrograms/l, 8.6 to 148.1 micrograms/l, 1.67 to 102.3 micrograms/24 h, < 0.05 to 22.93 micrograms/l, and 0.21 to 7.80 micrograms/l, respectively. The variation in all results presented is probably a reflection of different environmental contamination with trichloroethylene and tetrachloroethylene in the different city areas. Correlation analyses revealed significant relationships between trichloroethylene and tetrachloroethylene in blood (r = .402, p = .0004); trichloroacetic acid in urine and in plasma (r = .522, p = .0000); and trichloroethylene and tetrachloroethylene in drinking water (r = .800, p = .0000). A division of all parameters into a subgroup (n = 58), taking drinking water concentrations of trichloroethylene above 3 micrograms/l as a basis, demonstrated the same significant relationships as mentioned above.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-term health effects of an industrial toxic waste landfill: a retrospective follow-up study in Montchanin, France

A retrospective follow-up study was conducted in 1990 to assess the short-term health impacts of an industrial waste landfill. The site, located since 1979 in a French town of 6,000 inhabitants (about 100 m from the nearest houses) released volatile organic compounds (VOCs) into the air and provoked intense health concern in the community. The landfill was subsequently closed in 1988. Subjects were 694 inhabitants residing in three different parts of town. Individual exposure was estimated, using a dispersion model of volatile air pollutants and accommodated the daily activity patterns of each individual within the area under investigation. Surrogate morbidity data were derived from measurement of the consumption of drugs prescribed for specific therapeutic categories over a 3-y period (18 mo before and 18 mo after the site was closed). Although differences were not statistically significant, the most exposed subjects had been prescribed more drugs for diseases possibly linked to emissions from the site before it closed than the least exposed individuals. There was a suggestion of a slight trend in the consumption of drugs for ear, nose, and throat and pulmonary ailments with individual exposure levels. These results, and the review of toxicological data for some of the VOCs released by the dump, support the decision to close the site.

Neurobehavioral testing of subjects exposed residentially to groundwater contaminated from an aluminum die-casting plant and local referents

Residents adjoining a die-casting plant had excessive headaches, numbness of hands and feet, dizziness, blurred vision, staggering, sweating, abnormal heart rhythm, and depression, which led to measurements of neurobehavioral performance, affective status, and the frequency of symptoms. They had all been exposed via well water and proximity to the plant to volatile organic chemicals (VOC) and to polychlorinated biphenyls (PCBs). The 117 exposed women and men and 46 unexposed referents were studied together for simple and choice visual reaction time, body sway speed, blink reflex latency, color discrimination, Culture Fair (a nonverbal nonarithmetic intelligence test), recall of stories, figures, and numbers, cognitive and psychomotor control (slotted pegboard and trail making A and B), long-term memory, profile of mood states (POMS), and scores and frequencies of 34 symptoms. Choice reaction time, sway speed, and blink latency were impaired in both sexes of the exposed group and trail making B was impaired in exposed women. The POMS scores and frequencies of 30 of 34 symptoms were elevated in both sexes, compared to referents. Recall, long-term memory, psychomotor speed, and other cognitive function tests were reduced in exposed subjects and in the referents as compared to national referents. Neurophysiological impairment, and cognitive and psychomotor dysfunction and affective disorders, especially depression and excessive frequency of symptoms, were associated with the use of wells contaminated with VOCs, TCE and PCBs.

Effects on neurobehavioral performance of chronic exposure to chemically contaminated well water

Occupational exposure to trichloroethylene (TCE) and other solvents impairs neurobehavioral performance. Use of well water contaminated with TCE and solvents has been associated with excessive symptoms, cancers, birth defects and impaired blink reflex. We extended these observations by measuring the neurophysiological (NPH) and neuropsychological (NPS) status of subjects who used water contaminated with 6 to 500 ppb of TCE for 1 to 25 years. The 170 well-water exposed subjects who resided in southwest Tucson, Arizona overlying the Santa Cruz River aquifer, were compared to 68 referent subjects for NPH and NPS tests. Also, 113 histology technicians (HT) were referents for blink reflex latency only. Affective status was assayed by a Profile of Mood States (POMS). Exposed subjects were statistically significantly impaired when compared to referents for NPH tests. These impairments included sway speed with eyes open and closed, blink reflex latency (R-1), eye closure speed, and two choice visual reaction time. NPS status was statistically significant impaired for Culture Fair (intelligence) scores, recall of stories, visual recall, digit span, block design, recognition of fingertip numbers, grooved pegboard and Trail making A and B. POMS scores were elevated. Prolonged residential exposure to well-water containing TCE at lower levels than occupational exposures, but without time away from exposure for metabolism and excretion of toxins, was associated with neurobehavioral impairment.

Blink reflex measurement of effects of trichloroethylene exposure on the trigeminal nerve

Trichloroethylene (TCE) exposure is known to have specific toxic effects on cranial nerves, the trigeminal nerve (V) in particular. The electrophysiological measurement of the blink reflex (BR) can quantify latency changes in the Vth and VIIth cranial nerve reflex arc. Prior study looked at the blink reflex measurement in a community group exposed to TCE in their drinking water. This study evaluated the use of the electrophysiologic blink reflex as an indicator of neurotoxic effects of TCE in occupationally exposed workers. The BR was tested in individual cases with documented histories of exposure to known chemical neurotoxins including TCE (n = 18). When compared with the nonexposed laboratory control values (n = 30), the subjects with a significant history of TCE exposure demonstrated the most prolonged latencies (greater than or equal to 3.0 SD above the nonexposed group mean) in the R1 component of the blink reflex measurement. The electrophysiological study of the blink reflex has application in assessing TCE exposure and in documenting the neurotoxic effects of that exposure on trigeminal nerve functions in humans.

Consideration of the target organ toxicity of trichloroethylene in terms of metabolite toxicity and pharmacokinetics

Trichloroethylene (TRI) is readily absorbed into the body through the lungs and gastrointestinal mucosa. Exposure to TRI can occur from contamination of air, water, and food; and this contamination may be sufficient to produce adverse effects in the exposed populations. Elimination of TRI involves two major processes: pulmonary excretion of unchanged TRI and relatively rapid hepatic biotransformation to urinary metabolites. The principal site of metabolism of TRI is the liver, but the lung and possibly other tissues also metabolize TRI, and dichlorovinyl-cysteine (DCVC) is formed in the kidney. Humans appear to metabolize TRI extensively. Both rats and mice also have a considerable capacity to metabolize TRI, and the maximal capacities of the rat versus the mouse appear to be more closely related to relative body surface areas than to body weights. Metabolism is almost linearly related to dose at lower doses, becoming dose dependent at higher doses, and is probably best described overall by Michaelis-Menten kinetics. Major end metabolites are trichloroethanol (TCE), trichloroethanol-glucuronide, and trichloroacetic acid (TCA). Metabolism also produces several possibly reactive intermediate metabolites, including chloral, TRI-epoxide, dichlorovinyl-cysteine (DCVC), dichloroacetyl chloride, dichloroacetic acid (DCA), and chloroform, which is further metabolized to phosgene that may covalently bind extensively to cellular lipids and proteins, and, to a much lesser degree, to DNA. The toxicities associated with TRI exposure are considered to reside in its reactive metabolites. The mutagenic and carcinogenic potential of TRI is also generally thought to be due to reactive intermediate biotransformation products rather than the parent molecule itself, although the biological mechanisms by which specific TRI metabolites exert their toxic activity observed in experimental animals and, in some cases, humans are not known. The binding intensity of TRI metabolites is greater in the liver than in the kidney. Comparative studies of biotransformation of TRI in rats and mice failed to detect any major species or strain differences in metabolism. Quantitative differences in metabolism across species probably result from differences in metabolic rate and enterohepatic recirculation of metabolites. Aging rats have less capacity for microsomal metabolism, as reflected by covalent binding of TRI, than either adult or young rats. This is likely to be the same in other species, including humans. The experimental evidence is consistent with the metabolic pathways for TRI being qualitatively similar in mice, rats, and humans. The formation of the major metabolites--TCE, TCE-glucuronide, and TCA--may be explained by the production of chloral as an intermediate after the initial oxidation of TRI to TRI-epoxide.(ABSTRACT TRUNCATED AT 400 WORDS)