Peripheral neuropathy caused by arsenical intoxication; a study of 41 cases with observations on the effects of BAL (2, 3, dimercapto-propanol)

Arsenic and Tau Phosphorylation: a Mechanistic Review

Arsenic poisoning can affect the peripheral nervous system and cause peripheral neuropathy. Despite different studies on the mechanism of intoxication, the complete process is not explained yet, which can prevent further intoxication and produce effective treatment. In the following paper, we would like to consider the idea that arsenic might cause some diseases via inflammation induction, and tauopathy in neurons. Tau protein, one of the microtubule-associated proteins expressed in neurons, contributes to neuronal microtubules structure. Arsenic may be involved in cellular cascades involved in modulating tau function or hyperphosphorylation of tau protein, which ultimately leads to nerve destruction. For proof of this assumption, some investigations have been planned to measure the association between arsenic and quantities of phosphorylation of tau protein. Additionally, some researchers have investigated the association between microtubule trafficking in neurons and the levels of tau protein phosphorylation. It should be noticed that changing tau phosphorylation in arsenic toxicity may add a new feature to understanding the mechanism of poisonousness and aid in discovering novel therapeutic candidates such as tau phosphorylation inhibitors for drug development.

Molecular Mechanism of Arsenic-Induced Neurotoxicity including Neuronal Dysfunctions

Arsenic is a key environmental toxicant having significant impacts on human health. Millions of people in developing countries such as Bangladesh, Mexico, Taiwan, and India are affected by arsenic contamination through groundwater. Environmental contamination of arsenic leads to leads to various types of cancers, coronary and neurological ailments in human. There are several sources of arsenic exposure such as drinking water, diet, wood preservatives, smoking, air and cosmetics, while, drinking water is the most explored route. Inorganic arsenic exhibits higher levels of toxicity compared its organic forms. Exposure to inorganic arsenic is known to cause major neurological effects such as cytotoxicity, chromosomal aberration, damage to cellular DNA and genotoxicity. On the other hand, long-term exposure to arsenic may cause neurobehavioral effects in the juvenile stage, which may have detrimental effects in the later stages of life. Thus, it is important to understand the toxicology and underlying molecular mechanism of arsenic which will help to mitigate its detrimental effects. The present review focuses on the epidemiology, and the toxic mechanisms responsible for arsenic induced neurobehavioral diseases, including strategies for its management from water, community and household premises. The review also provides a critical analysis of epigenetic and transgenerational modifications, mitochondrial oxidative stress, molecular mechanisms of arsenic-induced oxidative stress, and neuronal dysfunction.

Arsenic Poisoning due to High Consumption of Canned Sardines in Jeddah, Saudi Arabia

Dietary consumption of arsenic is considered the largest source of toxicosis for nonoccupationally exposed individuals as it can be ingested through contaminated underground water, seafood, animal products, and crops irrigated with polluted water. We present a case of a 45-year-old Caucasian male who had headaches and peripheral neuropathy for more than two months. He suspected arsenic poisoning as he has a regular heavy consumption of seafood and canned sardines. Analysis of urinary arsenic concentration confirmed his intoxication with arsenic. Yet, since it was of an inorganic form, he was prescribed with symptomatic treatments only. A symmetrical sensory or motor polyneuropathy featuring more distal impairment is among the most common neurological findings induced by arsenic toxicosis. Hence, a presenting history of heavy seafood diet should raise the differential diagnosis of arsenic or heavy metal poisoning and to investigate accordingly. This case illustrates the importance of taking the dietary regime of any patient presenting with neuropathy. In addition, the authorities must impose further rigorous surveillance and strict safety measures on food products and staples to minimize any sources of contamination of any sorts.

Subacute Arsenic Neuropathy: Clinical and Electrophysiological Observations

We report a patient who developed subacute peripheral neuropathy following ingestion of a traditional medicine for obesity. A 9-year-old girl who had a residual equinus varus deformity and sphincter disturbance due to pelvic ganglioneuroma presented with subacute sensorimotor peripheral neuropathy of 2 weeks duration. Her symptoms started 3 weeks after she started taking a locally made traditional medicine for obesity. She had no other systemic features of arsenic toxicity. She had Mee's lines on her nails and high serum arsenic levels and 24-hour urine levels confirmed the diagnosis of arsenic neuropathy. Nerve conduction study on admission demonstrated axonal sensorimotor neuropathy with slowed conduction velocity. She was not given any specific treatment and recovery was slow. At 18 months, she showed complete recovery and electrodiagnostic parameters returned to normal values. Arsenic is a known ingredient of many Indian ethnic remedies and possibility of arsenic neuropathy should be thought of in patients presenting with acute or sub-acute peripheral neuropathy of unknown etiology.

An Unusual Case of Acute Psychosis With Obsessive-Compulsive Features Following Arsenic Poisoning

Arsenic exposure, particularly the chronic type, can lead to poisoning with manifestations presenting in multiple organ systems. However, acute psychosis is not a commonly described manifestation of arsenic exposure. In this report, we present the case of a patient who developed acute psychosis with hallucinations, disorganized thinking, and obsessive-compulsive symptoms following chronic occupational arsenic exposure. The patient was treated with the combination of an antipsychotic and an antidepressant and he responded well with significant improvement in both the acute psychosis and obsessive-compulsive symptoms. The authors concluded that patients can develop atypical symptoms, including acute psychosis, following arsenic poisoning. In the case described in this report, the patient also presented with a new onset of obsessive-compulsive symptoms. Given this rare manifestation of arsenic poisoning for which there is no clearly defined treatment regimen, this case suggests that the use of a combination of an antipsychotic and an antidepressant may be considered in the rare event of psychosis with obsessive-compulsive features following arsenic poisoning.

Biological and environmental hazards associated with exposure to chemical warfare agents: arsenicals

Arsenicals are highly reactive inorganic and organic derivatives of arsenic. These chemicals are very toxic and produce both acute and chronic tissue damage. On the basis of these observations, and considering the low cost and simple methods of their bulk syntheses, these agents were thought to be appropriate for chemical warfare. Among these, the best-known agent that was synthesized and weaponized during World War I (WWI) is Lewisite. Exposure to Lewisite causes painful inflammatory and blistering responses in the skin, lung, and eye. These chemicals also manifest systemic tissue injury following their cutaneous exposure. Although largely discontinued after WWI, stockpiles are still known to exist in the former Soviet Union, Germany, Italy, the United States, and Asia. Thus, access by terrorists or accidental exposure could be highly dangerous for humans and the environment. This review summarizes studies that describe the biological, pathophysiological, toxicological, and environmental effects of exposure to arsenicals, with a major focus on cutaneous injury. Studies related to the development of novel molecular pathobiology-based antidotes against these agents are also described.

Neurosensory effects of chronic human exposure to arsenic associated with body burden and environmental measures

Exposure to arsenic in drinking water is known to produce a variety of health problems, including peripheral neuropathy. Auditory, visual and somatosensory impairment have been reported in Mongolian farmers living in the Yellow River Valley, where drinking water is contaminated by arsenic. In the present study, sensory tests, including pinprick and vibration thresholds, were administered to 320 residents with well-water arsenic levels, ranging from non-detectable to 690 μg/L. Vibration thresholds in the second and fifth fingers of both hands were measured using a vibrothesiometer. Drinking water, urine and toenail samples were obtained to assess arsenic exposure and body burden. Regression analyses indicated significant associations of pinprick scores and vibration thresholds with all arsenic measures. Vibration thresholds were more strongly associated with urinary than water or nail arsenic measures, but odds ratios for decreased pinprick sensitivity were highest for the water arsenic measure. Results of the current study indicate neurosensory effects of arsenic exposure at concentrations well below the 1000 μg/L drinking water level specified by NRC, and suggest that non-carcinogenic end-points, such as vibration thresholds, are useful in the risk assessment of exposure to arsenic in drinking water.

Prolonged central sensory conduction time in patients with chronic arsenic exposure

BACKGROUND

Many patients from Toroku, Japan, who have chronic arsenic exposure demonstrate whole-body sensory disturbance that is slightly more pronounced in the extremities. Although previous research in this population showed a mild peripheral neuropathy, it is unknown whether these patients have central nervous system impairment. To investigate the lesion sites underlying sensory disturbance related to chronic arsenic poisoning, we analyzed somatosensory evoked potentials (SEP).

METHODS

Clinical features, nerve conduction study results, and median and/or tibial SEP were analyzed in patients with chronic arsenic exposure (total, 13 patients; median & tibial, 4; median, 5; tibial, 4) retrospectively. The SEP findings in patients were compared with those in normal controls.

RESULTS

The median SEP results indicated a conduction delay between the proximal brachial plexus and the primary sensory cortex, and tibial SEP findings indicated a delay between the dorsal gray matter of the lumbosacral cord and the primary sensory cortex.

CONCLUSION

This is the first study to identify an impairment of the central somatosensory pathway in patients with chronic arsenic exposure. Sensory disturbance in these patients is related not only to peripheral neuropathy but also to impairment of the central nervous system.

Heavy metal chelation in neurotoxic exposures

Metals such as iron and copper are critical to living organisms, whereas other metals such as lead and arsenic have no known biologic role. Any metals in large amounts may cause toxicity. Many metals cause pervasive systemic effects involving the nervous system, which can be subtle in some cases. Although challenging, the diagnosis and treatment of metal poisoning can be made based on history, physical examination, and the proper use of metal testing. This article focuses on the use, and misuse, of chelation in the diagnosis and management of metal intoxication.

Murshidabad—One of the Nine Groundwater Arsenic-Affected Districts of West Bengal, India. Part II: Dermatological, Neurological, and Obstetric Findings

INTRODUCTION

To understand the severity of related health effects of chronic arsenic exposure in West Bengal, a detailed 3-year study was carried out in Murshidabad, one of the nine arsenic-affected districts in West Bengal.

METHODS

We screened 25,274 people from 139 arsenic-affected villages in Murshidabad to identify patients suffering from chronic arsenic toxicity for evidence of multisystemic features and collected biological samples such as head hair, nail, and spot urine from the patients along with the tubewell water they were consuming.

RESULTS

Out of 25,274 people screened, 4813 (19%) were registered with arsenical skin lesions. A case series involving arsenical skin lesions resulting in cancer and gangrene were noted during this study. Representative histopathological pictures of skin biopsy of different types of lesions were also presented. Out of 2595 children we examined for arsenical skin lesions, 122 (4%) were registered with arsenical skin lesions, melanosis with or without keratosis. Different clinical and electrophysiological neurological features were noticed among the arsenic-affected villagers. Both the arsenic content in the drinking water and duration of exposure may be responsible in increasing the susceptibility of pregnant women to spontaneous abortions, stillbirths, preterm births, low birth weights, and neonatal deaths. Some additional multisystemic features such as weakness and lethargy, chronic respiratory problems, gastrointestinal symptoms, and anemia were also recorded in the affected population.

DISCUSSION

The findings from this survey on different health effects of arsenic exposure were compared to those from previous studies carried out on arsenic-affected populations in India and Bangladesh as well as other affected countries.

CONCLUSION

Multisystemic disorders, including dermal effects, neurological complications, and adverse obstetric outcomes, were observed to be associated with chronic arsenic exposure in the study population in Murshidabad, West Bengal. The magnitude of severity was related to the concentration of arsenic in water as well as duration of the exposure.

Interventions for preventing non-melanoma skin cancers in high-risk groups

BACKGROUND

Some groups of people have a greater risk of developing common non-melanoma skin cancers (NMSC).

OBJECTIVES

To evaluate interventions for preventing NMSC in people at high risk of developing NMSC.

SEARCH STRATEGY

We searched the Cochrane Skin Group Specialised Register (March 2007), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2007, MEDLINE (from 2003 to March 2007), EMBASE (from 2005 to March 2007), the metaRegister of Controlled Trials (February 2007). References from trials and reviews were also searched. Pharmaceutical companies were contacted for unpublished trials.

SELECTION CRITERIA

Randomised controlled trials of adults and children at high risk of developing NMSC.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies and assessed their methodological quality.

MAIN RESULTS

We identified 10 trials (7,229 participants) that assessed a variety of interventions. One trial found T4N5 liposome lotion significantly reduced the rate of appearance of new BCCs in people with xeroderma pigmentosum. One of three trials of renal transplant recipients showed a significantly reduced risk of new NMSCs when acitretin was compared to placebo (relative risk (RR) 0.22 95% confidence interval (CI) 0.06 to 0.90) and no significant difference in risk of adverse events in two trials (RR 1.80, 95% CI 0.70 to 4.61). In three trials conducted in people with a history of NMSC, the evidence was inconclusive for the development of BCCs for retinol or isoretinoin. However the risk of a new SCC in one trial (HR 1.79, 95% CI 1.16 to 2.76) and adverse events in another trial (RR 1.76 95% CI 1.57 to 1.97) were significantly increased in the isotretinoin group compared with placebo. In one trial selenium showed a reduced risk of other types of cancer compared with placebo (RR 0.65, 95% CI 0.50 to 0.85) but also a significantly elevated risk of a new NMSC (HR 1.17 95% CI 1.02 to 1.34). The evidence for one trial of beta-carotene was inconclusive; and there was a trend towards fewer new NMSC in a trial of a reduced fat diet (RR 0.16, 95% CI 0.02 to 1.31), p=0.09.

AUTHORS' CONCLUSIONS

Some preventative treatments may benefit people at high risk of developing NMSC, but the ability to draw firm conclusions is limited by small numbers of trials, often with one trial per intervention or with inconsistent results between studies.

Slow recovery from severe inorganic arsenic poisoning despite treatment with DMSA (2.3-dimercaptosuccinic acid)

A 39-year-old woman was hospitalized for nausea, diarrhea, vomiting, and weakness of unknown etiology. Her condition progressively deteriorated and she developed multiple organ failure and tetraplegia. The diagnosis of inorganic arsenic poisoning was established by measurements of arsenic in urine and serum, showing 2,000 microg/L (normal < 10 microg/L) and 290 mug/Kg (normal < 2 microg/Kg), respectively. Hair arsenic was 57 mg/kg (normal < 0.2 mg/kg). Chelating therapy with 2.3-dimercaptosuccinic acid (DMSA) 600 mg three times daily was given for a period of 45 days with three abruption periods during a total of 13 days. The clinical manifestations of arsenic toxicosis disappeared very slowly and five years after the hospitalization she still suffers from peripheral neuropathy. Although the use of DMSA was associated with increased urinary elimination of arsenic and a decrease in blood arsenic concentrations, DMSA treatment probably had no significant effect on the total body clearance in our patient. The source of the poisoning was never detected, nor the motivation behind it. Criminal intent was suspected, but no verdict was given.

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.

Case report: potential arsenic toxicosis secondary to herbal kelp supplement

CONTEXT

Medicinal use of dietary herbal supplements can cause inadvertent arsenic toxicosis.

CASE PRESENTATION

A 54-year-old woman was referred to the University of California, Davis, Occupational Medicine Clinic with a 2-year history of worsening alopecia and memory loss. She also reported having a rash, increasing fatigue, nausea, and vomiting, disabling her to the point where she could no longer work full-time. A thorough exposure history revealed that she took daily kelp supplements. A urine sample showed an arsenic level of 83.6 microg/g creatinine (normal < 50 microg/g creatinine). A sample from her kelp supplements contained 8.5 mg/kg (ppm) arsenic. Within weeks of discontinuing the supplements, her symptoms resolved and arsenic blood and urine levels were undetectable.

DISCUSSION

To evaluate the extent of arsenic contamination in commercially available kelp, we analyzed nine samples randomly obtained from local health food stores. Eight of the nine samples showed detectable levels of arsenic higher than the Food and Drug Administration tolerance level of 0.5 to 2 ppm for certain food products. None of the supplements contained information regarding the possibility of contamination with arsenic or other heavy metals. The 1994 Dietary Supplement Health and Education Act (DSHEA) has changed the way dietary herbal therapies are marketed and regulated in the United States. Less regulation of dietary herbal therapies will make inadvertent toxicities a more frequent occurrence.

RELEVANCE TO CLINICAL PRACTICE

Clinicians should be aware of the potential for heavy metal toxicity due to chronic use of dietary herbal supplements. Inquiring about use of dietary supplements is an important element of the medical history.

Arsenic in drinking water and peripheral nerve conduction velocity among residents of a chronically arsenic-affected area in Inner Mongolia

Background

It remains unclear whether chronic ingestion of arsenic in drinking water affects the peripheral nervous system. We examined the effects of arsenic exposure on nerve conduction velocity using electromyography.

Methods

A cross-sectional study was conducted of a population living in an arsenic-affected village in Hetao Plain, Inner Mongolia, China. A total of 134 (93.7%) of 143 inhabitants took part in the study, and 36 (76.6%) of 47 inhabitants in a low-arsenic exposed village were recruited as a control group. Of the participants, 109 inhabitants in the arsenic-affected village and 32 in the low-arsenic exposed village aged ≥18 years were used for the analyses. An expert physician performed skin examinations, and median nerve conduction velocity was examined by electromyography. Arsenic levels in tube-well water and urine were measured. A mean level of arsenic in tube-well water in the arsenic-affected village was 158.3μg/L, while that in the low-arsenic exposed village was 5.3μg/L.

Results

No significant differences in the means of the motor nerve conduction velocity (MCV) and sensory nerve conduction velocity (SCV) were observed in relation to arsenic levels in tube wells, urine, and the duration of tube-well use. Further, no differences in mean MCV or SCV were found between the subjects with and without arsenic dermatosis, with mean SCV of 52.8 m/s (SD 6.3) in those without and 54.6 m/s (5.2) in subjects with arsenic dermatosis (p=0.206).

Conclusion

These findings suggest that chronic arsenic poisoning from drinking water is unlikely to affect nerve conduction velocity, at least within the range of arsenic in drinking water examined in the present study.

Persistent Neuropathy and Hyperkeratosis from Distant Arsenic Exposure

The purpose of this case series is to assess long-term sequelae of arsenic exposure in a cohort acutely exposed to arsenic in drinking water from a well dug into a landfill containing arsenical pesticides. Ten of the 13 individuals (or next of kin) in the initial study agreed to participate in the follow-up study. Next of kin provided questionnaire data and released medical information on the three individuals who had died. The remaining seven cohort members were assessed by an interview, questionnaire, detailed physical examination and sensory nerve testing. Available medical records were obtained and reviewed. Sensory testing was performed using an automated electrodiagnostic sensory Nerve Conduction Threshold (sNCT) evaluation. Sensory complaints and electrodiagnostic findings consistent with polyneuropathy were found in a minority (3/7) of subjects 28 years after an acute toxic arsenic exposure. Two of the seven patients examined (1 of 3 with neuropathic findings) also had hyperkeratotic lesions consistent with arsenic toxicity and one of the patients had hyperpigmentation on their lower extremities possibly consistent with arsenic toxicity.

Arsenic contamination in Bangladesh groundwater: a major environmental and social disaster

In attempting to eliminate disease caused by drinking polluted surface water, millions of shallow surface wells were drilled into the Ganges delta alluvium in Bangladesh. The latest statistics indicate that 80% of Bangladesh and an estimated 40 million people are at risk of arsenic poisoning-related diseases because the ground water in these wells is contaminated with arsenic. The clinical manifestations of arsenic poisoning are myriad, and the correct diagnosis depends largely on awareness of the problem. Patients with melanosis, leuco-melanosis, keratosis, hyperkeratosis, dorsum, non-petting edema, gangrene and skin cancer have been identified. The present article reviews the current arsenic contamination of ground water, hydrological systems, groundwater potential and utilization and environmental pollution in Bangladesh. This paper concludes by clarifying the main actions required to ensure the sustainable development of water resources in Bangladesh.

Chronic arsenic toxicity in Bangladesh and West Bengal, India--a review and commentary

Fifty districts of Bangladesh and 9 districts in West Bengal, India have arsenic levels in groundwater above the World Health Organization's maximum permissible limit of 50 microg/L. The area and population of 50 districts of Bangladesh and 9 districts in West Bengal are 118,849 km2 and 104.9 million and 38,865 km2 and 42.7 million, respectively. Our current data show arsenic levels above 50 microg/ L in 2000 villages, 178 police stations of 50 affected districts in Bangladesh and 2600 villages, 74 police stations/blocks of 9 affected districts in West Bengal. We have so far analyzed 34,000 and 101,934 hand tube-well water samples from Bangladesh and West Bengal respectively by FI-HG-AAS of which 56% and 52%, respectively, contained arsenic above 10 microg/L and 37% and 25% arsenic above 50 microg/L. In our preliminary study 18,000 persons in Bangladesh and 86,000 persons in West Bengal were clinically examined in arsenic-affected districts. Of them, 3695 (20.6% including 6.11% children) in Bangladesh and 8500 (9.8% including 1.7% children) in West Bengal had arsenical dermatological features. Symptoms of chronic arsenic toxicity developed insidiously after 6 months to 2 years or more of exposure. The time of onset depends on the concentration of arsenic in the drinking water, volume of intake, and the health and nutritional status of individuals. Major dermatological signs are diffuse or spotted melanosis, leucomelanosis, and keratosis. Chronic arsenicosis is a multisystem disorder. Apart from generalized weakness, appetite and weight loss, and anemia, our patients had symptoms relating to involvement of the lungs, gastrointestinal system, liver, spleen, genitourinary system, hemopoietic system, eyes, nervous system, and cardiovascular system. We found evidence of arsenic neuropathy in 37.3% (154 of 413 cases) in one group and 86.8% (33 of 38 cases) in another. Most of these cases had mild and predominantly sensory neuropathy. Central nervous system involvement was evident with and without neuropathy. Electrodiagnostic studies proved helpful for the diagnosis of neurological involvement. Advanced neglected cases with many years of exposure presented with cancer of skin and of the lung, liver, kidney, and bladder. The diagnosis of subclinical arsenicosis was made in 83%, 93%, and 95% of hair, nail and urine samples, respectively, in Bangladesh; and 57%, 83%, and 89% of hair, nail, and urine samples, respectively in West Bengal. Approximately 90% of children below 11 years of age living in the affected areas show hair and nail arsenic above the normal level. Children appear to have a higher body burden than adults despite fewer dermatological manifestations. Limited trials of 4 arsenic chelators in the treatment of chronic arsenic toxicity in West Bengal over the last 2 decades do not provide any clinical, biochemical, or histopathological benefit except for the accompanying preliminary report of clinical benefit with dimercaptopropanesulfonate therapy. Extensive efforts are needed in both countries to combat the arsenic crisis including control of tube-wells, watershed management with effective use of the prodigious supplies of surface water, traditional water management, public awareness programs, and education concerning the apparent benefits of optimal nutrition.

Recovery from severe arsenic-induced peripheral neuropathy with 2,3-dimercapto-1-propanesulphonic acid

CASE REPORT

A 33-year-old female with a 1.5-year history of multisystem illness was diagnosed with arsenic poisoning. Twenty-four-hour urine arsenic was 1030 microg/dL (normal 0-99) and root hair arsenic was 130 microg/g (normal 0-3). Despite treatment with succimer meso-2,3-dimercaptosuccinic acid, her neuropathy progressed to ventilator dependence and quadriplegia. Subsequent intravenous treatment with 2,3-dimercapto-1-propanesulfonic acid sodium salt was associated with arsenic diuresis, marked neuropathic improvement, and extubation. At 1-year follow-up, neuropathy was limited to mild distal lower extremity weakness and sensory loss. The use of 2,3-dimercapto-1-propanesulphonic acid in the treatment of severe arsenic neuropathy was associated with increased urinary elimination of arsenic and dramatic clinical recovery.

Organic arsenic intoxication from bird's nest soup

OBJECTIVE

To present a case of organic arsenic intoxication after consumption of bird's nest soup in a Vietnamese patient.

METHOD

We have described the clinical picture of a patient with organic arsenic intoxication, and high levels of urine arsenic after consumption of bird's nest soup.

RESULT

Withdrawal of bird's nest soup coincided with a decrease in urinary arsenic levels and the disappearance of peripheral neuropathy.

CONCLUSION

This case illustrates the environmental contamination of bird's nest soup with organic arsenic. A prompt removal of the source from the diet resulted in clinical improvement.

Heavy metal toxicity, Part I: arsenic and mercury

This review is Part I of a two-part series focusing on heavy metal toxicity. Part I will cover arsenic and mercury toxicity. Acute and chronic arsenic toxicity, as well as arsine gas toxicity, will be reviewed. The clinical presentation, with focus on the nervous, cardiovascular, pulmonary, gastrointestinal, hepatic, renal, hematopoietic, and dermatologic systems, is delineated. Mercury exposure, including exposure to short chain alkyl mercury, elemental mercury, and acute inorganic salt, is reviewed. The discussion of clinical toxicity focuses on the nervous, cardiovascular, pulmonary, gastrointestinal, and renal systems, as well as on the teratogenic effects of mercury. Recommendations for diagnostic tests and management plans are discussed, including chelation regimens.

Acquired peripheral neuropathy

This article reviews the acquired causes of polyneuropathy other than diabetic and acute-onset neuropathies. The author gives a general method to simplify the diagnosis of chronic polyneuropathy. The acquired polyneuropathies are discussed under four main headings: metabolic disorders, toxic or deficiency states, infections, and immune-mediated. Recent advances in therapy are emphasized, and some illustrative case histories are provided.

Premalignant keratinocytic neoplasms

Premalignant keratinocytic keratoses are common, especially in pale-complected persons in whom they appear most often as an actinic keratosis. Although the actinic keratosis has a very low malignant potential, arsenic, tar, thermal, scar, reactional, and radiation keratoses may be more clinically aggressive. This article discusses these premalignant keratinocytic neoplasms.

Environmental aspects of arsenic toxicity

The toxicity of arsenic and its long history of use in human culture has resulted in widespread concern about the natural and anthropogenic levels of arsenic in our environment. In this article, an overview of the current environmental status of arsenic is presented. A brief history of the usage of this element is followed by a discussion of the current applications. Both natural as well as anthropogenic sources of input are described and discussed in terms of their relative impact on the Earth's environment. Numerous control mechanisms for arsenic exist in the environment, and the major processes involved (physical, chemical, and biological) are highlighted. Natural cycling of this element through the various environmental compartments (air, water, soil, and biota) are described as well as some current methods for the removal of arsenic from natural and industrial waters. Finally, a brief overview of the most common methods for the analysis of arsenic in environmental samples is presented.

Assessment of exposure to arsenic among smelter workers: a five-year follow-up

In a group of 43 smelter workers exposed to inorganic arsenic dust for 13-45 years, nerve conduction velocities (NCVs) were significantly lower in two peripheral nerves as compared with matching referents. With multivariate data analysis, a significant negative correlation was found between cumulative absorption of arsenic and NCV in four examined nerves and the sural amplitude. Clinical symptoms of neuropathy and other symptoms related to arsenic exposure were moderate, though the difference between the groups was significant. The mean total absorption of arsenic was calculated to be less than 5 g, and the maximal absorption about 20 g. These data indicate that the adverse effect of arsenic on the peripheral nerves is dependent on long-term exposure rather than on short-term fluctuations in exposure levels.

A seasonal study of arsenic in groundwater, Snohomish County, Washington, USA

A series of arsenic poisonings near Granite Falls in Snohomish County, Washington, were identified during 1985-87. An initial investigation revealed the source of arsenic exposure to be high levels of arsenic in well water. A large number of wells in eastern Snohomish County were tested, residents were interviewed and sources of contamination, both natural and man-made, were investigated. More than 70 private drinking-water wells were found to contain elevated levels of arsenic . One well contained 33 mg As L(-1). The finding of elevated arsenic levels in a previously approved drinking-water well for a restaurant, plus suggestions of symptoms consistent with arsenic poisoning among people with wells with no detectable arsenic, raised concern over possible temporal variation in arsenic levels. To evaluate this temporal variation, a 12-month study of arsenic in groundwater was conducted in selected wells near Granite Falls. The 12-month study of 26 wells, conducted between February 1988 and January 1989, found arsenic levels for individual wells to vary from one to 19 fold over time. Because of this variability, four out of the eight wells with arsenic levels close to the Maximum Contamination Level (MCL) of 0.050 mg As L(-1) would have been considered safe on the basis of a single sample, but would have exceeded the MCL at another time of the year.In areas with a high occurrence of arsenic contaminated drinking water, approval of well water prior to the sale of a house or issuance of a building permit which is based on a single arsenic test may result in later findings of unacceptable drinking water. When the arsenic is near the MCL, it may be prudent to follow well-water arsenic concentrations over time to assure that the arsenic level remains within acceptable bounds. If lower arsenic standards are adopted for drinking water, the issue of temporal variation around the standard will become a matter of more widespread concern.

Clinical observations and medical outcome in 149 cases of arsenate ant killer ingestion

One hundred forty-nine (149) consecutive cases of arsenate-containing ant killer reported to the Minnesota Regional Poison Center over 4 1/2 months were retrospectively reviewed with a follow-up (1 week to 3 months) completed in 132 (89%) of the population studied. One hundred and forty eight (99%) of the ingestions were accidental. The majority of cases involved children 3 years of age and younger. Only three patients accidentally ingesting the product were symptomatic (mild episodes of vomiting and diarrhea which cleared in all patients within 12 hours). No patient was referred to a medical center for treatment and no patient reached on follow-up reported any additional ill effects as a result of the exposure. In addition to the 149 patients in this series, we describe two representative patients who accidentally ingested similar amounts of sodium arsenate-containing ant killer, resulting in urine arsenic of 3500 micrograms/24 h and 5819 micrograms/24 h. They required no chelation treatment and had no evident sequelae during 4-6 months of medical follow-up. This experience supports poison center directed home management for the majority of single, acute, and accidental ingestions of small quantities (< 5 mL) of arsenate-containing ant killers as a safe alternative to medical center referral and adverse reactions to chelation.

Non-carcinogenic effects of inorganic arsenic

This review will focus primarily on ohe effects of the inorganic arsenicals (arsenate and arsenite forms) that are present in drinking water. They are acutely toxic to both humans and animals, an effect that may be related to their bioavailibility. In humans, arsenicals have been reported to cause dermatitis and mucous membrane irritation upon exposure. They have also been reported to cause skin lesions and peripheral neurotoxicity in smelter workers and in patients treated with Fowler's Solution. When humans are exposed to arsenic in drinking water, effects such as hyperkeratosis, electromyographic abnormalities and vascular effects have been reported. In experimental animals, arsenic has been demonstrated to affect the liver and kidneys. In mice, arsenic has also been reported to decrease the animal's resistance to certain viral infections. The arsenite (+3) and arsenate (+5) forms have different modes of action. Arsenite binds to sulphhydryl groups and has been reported to inhibit over 100 different enzymes, while the arsenate can substitute for phosphate in various high energy intermediates, resulting in arsenolysis. In addition, when arsenate is reduced to arsenite in the body, it can also cause toxicity as that species.

Health response by questionnaire in arsenic-exposed populations

The health status of populations exposed to arsenic through drinking water was determined by a mailed questionnaire. Participants were selected from three communities located in Nevada with 1977 tap water arsenic levels of approximately 0.1 mg/l and one California community with 1977 levels around 0.39 mg/l. The questionnaire responses were obtained in 1979 from the four exposed communities and compared to those of a Wyoming community whose tap water levels of arsenic were less than 0.001 mg/l in 1979. No difference in health status for gastrointestinal, neurological, musculoskeletal, circulatory and skin disorders was found. The average number of years of consumption given by length of residence was 6-16 years. We conclude that the health status of these arsenic-exposed populations has not been adversely affected.

Electrophysiological profile in arsenic neuropathy

Comprehensive electrophysiological studies were performed on 13 patients with arsenic neuropathy. The most prominent finding was a marked abnormality in sensory nerve conduction in the presence of moderate abnormalities in motor nerve conduction. The motor nerve conduction studies and needle EMG were typical of those seen in axonal degeneration which was confirmed by sural nerve biopsy.

A new measuring design for autonomic dysfunction of skin in neuropathies: hyperthermal laser-Doppler flowmetry

Twenty patients suffering from diabetic neuropathy, 20 patients suffering from alcoholic neuropathy and 20 healthy volunteers within the same age range were studied for the stimulability of microcirculation with a new measuring design. A laser method (laser-Doppler flowmetry) was used to evaluate the increase of the microvascular blood flow of the skin during the hyperthermal phase. It evaluated the degree of increase of microcirculatory blood flow as well as the time from the beginning of hyperthermy to the onset of change in perfusion (the hyperthermal perfusion latency). This was significantly prolonged in both neuropathy groups; the increase of the microvascular blood flow in the diabetic neuropathies was significantly lower than found in alcoholic neuropathies and in healthy volunteers.

Acute arsenic intoxication from environmental arsenic exposure

Reports of acute arsenic poisoning arising from environmental exposure are rare. Two cases of acute arsenic intoxication resulting from ingestion of contaminated well water are described. These patients experienced a variety of problems: acute gastrointestinal symptoms, central and peripheral neurotoxicity, bone marrow suppression, hepatic toxicity, and mild mucous membrane and cutaneous changes. Although located adjacent to an abandoned mine, the well water had been tested for microorganisms only and was found to be "safe." Regulations for testing of water from private wells for fitness to drink are frequently nonexistent, or only mandate biologic tests for microorganisms. Well water, particularly in areas near mining activity, should be tested for metals.

Cyanide and arsenic poisoning by intravenous injection

A 29-year-old man was found unresponsive a few minutes after self-injecting undetermined amounts of potassium cyanide and sodium arsenite intravenously in a suicide attempt. Treatment with the Lilly Cyanide Antidote kit rapidly resolved the initial coma, despite a whole blood cyanide level of 4.4 micrograms/mL. A 12-hour urine arsenic collection begun on admission showed 10,065 micrograms arsenic/12 hr. The patient received intramuscular BAL initially, which was followed by two ten-day courses of oral D-penicillamine. Complications included upper gastrointestinal tract bleeding requiring transfusion, transient elevations of liver function tests, self-limited complaints of decreased vision with conjunctival hyperemia and photophobia, and an abscess at the injection site. Although specific antidote therapy completely resolved the cyanide toxicity, early and prolonged arsenic chelation did not prevent a mild sensory peripheral neuropathy from developing with onset about 17 days after self-injection.

Survival following massive arsenic ingestion

A case of a 30-year-old man who ingested a massive quantity of arsenic (approximately 2,150 mg) in an apparent suicide attempt is presented. Aggressive initial therapy, including fluid resuscitation, chelation therapy, and hemodialysis, resulted in the patient's survival. The successful management of arsenic intoxication requires both prompt recognition and the initiation of specific and aggressive therapeutic modalities.

Long-term survival in acute arsenic encephalopathy. Follow-up using newer measures of electrophysiologic parameters

A 20-year-old man survived acute massive arsenic ingestion. The resultant severe encephalopathy and peripheral neuropathy showed limited long-term recovery over the following two years. The patient's clinical course was followed using visual and auditory evoked potentials, computed tomography, electroencephalography, and electromyography.

Acute arsenic intoxication presenting as Guillain-Barré-like syndrome

Arsenic-induced polyneuropathy is traditionally classified as an axonal-loss type, electrodiagnostically resulting in low amplitude or absent sensory and motor responses, relatively preserved proximal and distal motor conduction rates, and distal denervation. We report four patients with a subacute onset progressive polyradiculoneuropathy following high-dose arsenic poisoning. In three patients, early electrodiagnostic testing demonstrated findings suggestive of an acquired segmental demyelinating polyradiculoneuropathy. Serial testing confirmed evolution into features of a distal dying-back neuropathy. We hypothesize that arsenic toxicity and the resultant biochemical derangement of the peripheral nerve cell leads to subtle changes in axonal function that produce, initially, segmental demyelination and eventually distal axonal degeneration. Acute arsenic toxicity must be suspected in patients with clinical and electrodiagnostic features supporting Guillain-Barré syndrome.

Clinical and environmental aspects of arsenic toxicity

Arsenic is widely distributed throughout the animal and plant kingdoms and our environment where sources can be natural or anthropogenic. Agricultural uses of arsenic have declined recently, but it still has well-defined roles in industry. Small amounts of arsenic are metabolized in a variety of ways and are largely rapidly methylated and excreted by man and animals. Poisoning can occur and may follow an acute or chronic course. Toxic manifestations in man occur at the cellular level and may appear in many organ systems. Specific effects can often be demonstrated in the skin and in the vascular and nervous systems. Other toxic effects appear to include carcinogenesis, mutagenesis, and teratogenesis.

Unusual manifestations of arsenic intoxication

A patient with arsenic intoxication is reported, who presented with a variety of gastrointestinal and neurologic disturbances including unilateral facial nerve palsy and acute symptomatic pancreatitis, neither of which have been previously described as sequelae of arsenic poisoning. The patient also suffered hematologic, dermatologic, and cardiopulmonary complications. A review of the literature about this interesting problem is also presented.

Sentinel Health Events (occupational): a basis for physician recognition and public health surveillance

A Sentinel Health Event (SHE) is a preventable disease, disability, or untimely death whose occurrence serves as a warning signal that the quality of preventive and/or therapeutic medical care may need to be improved. A SHE (Occupational) is a disease, disability, or untimely death which is occupationally related and whose occurrence may: 1) provide the impetus for epidemiologic or industrial hygiene studies; or 2) serve as a warning signal that materials substitution, engineering control, personal protection, or medical care may be required. The present SHE(O) list encompasses 50 disease conditions that are linked to the workplace. Only those conditions are included for which objective documentation of an associated agent, industry, and occupation exists in the scientific literature. The list will serve as a framework for developing a national system for occupational health surveillance that may be applied at the state and local level, and as a guide for practicing physicians caring for patients with occupational illnesses. We expect to update the list periodically to accommodate new occupational disease events which meet the criteria for inclusion.

Neurologic evaluation of a population exposed to arsenic in Alaskan well water

One hundred forty-seven persons exposed to arsenic from well water were evaluated by neurologic examination and nerve conduction studies. Total arsenic concentrations in well water ranged from 1 to 4781 micrograms/L and from 6 to 4964 micrograms/L in urine; a calculated index of arsenic ingestion ranged from 1 to 4521 micrograms/day. No dose-response relationship existed between arsenic ingestion and symptoms or physical findings compatible with peripheral neuropathy. Five of six persons with symptoms or physical findings suggestive of sensory neuropathy had normal nerve conduction velocities. Thirteen persons with elevated arsenic ingestion but no signs or symptoms of neuropathy had one or more abnormal nerve conduction velocities. No dose-response relationship, however, existed between arsenic ingestion and nerve conduction velocities. The authors concluded that arsenic ingestion from well water at the concentrations found in this Alaskan community did not result in clinical or subclinical neuropathy.