CAR t-cell therapy in BOlogNa-NEUrotoxicity TReatment and Assessment in Lymphoma (CARBON-NEUTRAL): proposed protocol and results from an Italian study.

OBJECTIVE: To investigate neurotoxicity clinical and instrumental features, incidence, risk factors, and early and long-term prognosis in lymphoma patients who received CAR T-cell therapy. METHODS: In this prospective study, consecutive refractory B-cell non-Hodgkin lymphoma patients who received CAR T-cell therapy were included. Patients were comprehensively evaluated (neurological examination, EEG, brain MRI, and neuropsychological test) before and after (two and twelve months) CAR T-cells. From the day of CAR T-cells infusion, patients underwent daily neurological examinations to monitor the development of neurotoxicity. RESULTS: Forty-six patients were included in the study. The median age was 56.5 years, and 13 (28%) were females. Seventeen patients (37%) developed neurotoxicity, characterized by encephalopathy frequently associated with language disturbances (65%) and frontal lobe dysfunction (65%). EEG and brain FDG-PET findings also supported a predominant frontal lobe involvement. The median time at onset and duration were five and eight days, respectively. Baseline EEG abnormalities predicted ICANS development in the multivariable analysis (OR 4.771; CI 1.081-21.048; p = 0.039). Notably, CRS was invariably present before or concomitant with neurotoxicity, and all patients who exhibited severe CRS (grade ≥ 3) developed neurotoxicity. Serum inflammatory markers were significantly higher in patients who developed neurotoxicity. A complete neurological resolution following corticosteroids and anti-cytokines monoclonal antibodies was reached in all patients treated, except for one patient developing a fatal fulminant cerebral edema. All surviving patients completed the 1-year follow-up, and no long-term neurotoxicity was observed. CONCLUSIONS: In the first prospective Italian real-life study, we presented novel clinical and investigative insights into ICANS diagnosis, predictive factors, and prognosis.

Preliminary Risk assessment for Acrylamide and Peripheral Neuropathy.

Acrylamide (ACM) is a high-volume industrial chemical with diverse uses in manufacturing, construction and laboratory research. ACM is a well-established neurotoxic agent causing peripheral neuropathy with impairment in the arms and legs of exposed workers, most thoroughly studied in Swedish tunnel workers exposed to ACM grouting. A quantitative risk assessment was performed to assess ACM risk to workers. Using data from a published paper investigating peripheral neuropathies in Chinese chemical workers, estimates of exposure response for vibration perception threshold and nerve conduction velocities were calculated, based on hemoglobin adducts and air concentrations as exposure metrics. The benchmark dose procedure was applied in order to calculate excess risks of impairment, defined as adverse performance exceeding the 95th percentile in unexposed populations, at various concentrations of airborne ACM exposure. Under the assumptions in this risk assessment, after three years of inhalation exposure at 0.3 mg/m3, the excess attributable impairment manifest in vibration perception and nerve conduction velocity is estimated to occur in 1-2% of workers. For 10 years at 0.3 mg/m3 ACM inhalation (equivalent to 3 years at 1.0 mg/m3) the excess prevalence of impairment would be 2-14% of workers, assuming the effect continues to accrue linearly in time. Using published data, the risks of impairment from peripheral neuropathy attributable to exclusively airborne ACM exposure can be predicted for exposure periods less than 10 years. The risks associated with dermal and airborne ACM exposures can be estimated by characterizing working process environments using ACM Hb-adduct levels and possibly monitored with urinary biomarkers.

The updated five-year overall survival and long-term oxaliplatin-related neurotoxicity assessment of the FACOS study.

PURPOSE: We previously reported the first evidence of oncological benefits from a Japanese phase II trial of oxaliplatin-based adjuvant chemotherapy in patients with stage III colon cancer (the FACOS study). We herein report the long-term survival and persistent oxaliplatin-related peripheral sensory neuropathy (PSN) for patients enrolled in this trial. METHODS: Patients were scheduled to receive the mFOLFOX6 or CAPOX regimen in the adjuvant setting. The five-year overall survival (OS) rate and persistent PSN were evaluated. RESULTS: A total of 130 patients (mFOLFOX6, n = 73; CAPOX, n = 57) were eligible. The 5-year OS rate was 91.4%. No significant difference in the OS rate was observed between regimens (mFOLFOX6, 94.4%; CAPOX, 87.4%; P = 0.25). The incidence of PSN during adjuvant treatment was 55.4% in grade 1 (G1), 30.0% in G2, and 4.6% in G3. No patients showed G3 PSN at 12 months, but G1 or G2 residual PSN after 5 years was observed in 21.8% (G1, 20%; G2, 1.8%). CONCLUSIONS: Updated results from the FACOS study support the benefits of oxaliplatin-based adjuvant chemotherapy in terms of the long-term survival among Japanese patients with stage III colon cancer. However, long-term persistent PSN occurs in about 20% of survivors, counterbalancing the favorable OS.

Chemotherapy-induced peripheral neuropathy (CIPN) and its treatment: an NIH Collaboratory study of claims data.

PURPOSE: Chemotherapy-induced peripheral neuropathy (CIPN) is a disabling complication of many chemotherapies. We investigated the feasibility of using health plan claims and administrative data to identify CIPN occurrence by comparing patients who received neurotoxic and non-neurotoxic chemotherapies. METHODS: The sample included over 53,000,000 patients from two regional and one national insurer in the USA (> 400,000 exposed to chemotherapy). Peripheral neuropathy was identified using a broad definition (definition 1) and a specific definition (i.e., drug-induced polyneuropathy code) (definition 2). RESULTS: CIPN incidence as measured by definition 1 within 6 months of chemotherapy initiation was 18.1% and 6.2% for patients who received neurotoxic and non-neurotoxic chemotherapy, respectively (relative risk neurotoxic vs. non-neurotoxic (RR), 2.93 (95% CI, 2.87-2.98)). For definition 2, these incidences were 3.6% and 0.1% (RR, 25.2 (95% CI, 22.8-27.8)). The incidences of new analgesic prescriptions for neurotoxic and non-neurotoxic groups were as follows: gabapentin, 7.1%/1.7%; pregabalin, 0.69%/0.31%; and duloxetine, 0.78%/0.76%. The incidence of CIPN as defined by definitions 1 and 2 was low compared with that of published research studies, but the relative risk of CIPN among patients who received neurotoxic chemotherapies compared with those who received non-neurotoxic chemotherapies was high using definition 2. CONCLUSIONS: These data suggest that as used currently by clinicians, administrative codes likely underestimate CIPN incidence. Thus, studies using administrative data to estimate CIPN incidence are not currently feasible. However, the drug-induced polyneuropathy code is a specific indicator of CIPN in administrative data and may be useful for investigating predictors or potentially preventive therapies of CIPN.

Impact of chemotherapy-induced neurotoxicities on adult cancer survivors' symptom burden and quality of life.

PURPOSE: Limited information is available on the impact of chemotherapy (CTX)-induced neurotoxicity on adult survivors' symptom experience and quality of life (QOL). Purposes were to describe occurrence of hearing loss and tinnitus and evaluate for differences in phenotypic characteristics and measures of sensation, balance, perceived stress, symptom burden, and QOL between survivors who received neurotoxic CTX and did (i.e., neurotoxicity group) and did not (i.e., no neurotoxicity group) develop neurotoxicity. Neurotoxicity was defined as the presence of chemotherapy-induced neuropathy (CIN), hearing loss, and tinnitus. Survivors in the no neurotoxicity group had none of these conditions. METHODS: Survivors (n = 609) completed questionnaires that evaluated hearing loss, tinnitus, stress, symptoms, and QOL. Objective measures of sensation and balance were evaluated. RESULTS: Of the 609 survivors evaluated, 68.6% did and 31.4% did not have CIN. Of the survivors without CIN, 42.4% reported either hearing loss and/or tinnitus and 48.1% of the survivors with CIN reported some form of ototoxicity. Compared to the no neurotoxicity group (n = 110), survivors in the neurotoxicity group (n = 85) were older, were less likely to be employed, had a higher comorbidity burden, and a higher symptom burden, higher levels of perceived stress, and poorer QOL (all p < .05). CONCLUSIONS: Findings suggest that CIN, hearing loss, and tinnitus are relatively common conditions in survivors who received neurotoxic CTX. IMPLICATIONS FOR CANCER SURVIVORS: Survivors need to be evaluated for these neurotoxicities and receive appropriate interventions. Referrals to audiologists and physical therapists are warranted to improve survivors' hearing ability, functional status, and QOL.

Comprehensive risk assessment for early neurologic complications after liver transplantation.

AIM: To determine risk factors for early neurologic complications (NCs) after liver transplantation from perspective of recipient, donor, and surgeon. METHODS: In all, 295 adult recipients were enrolled consecutively between August 2001 and February 2014 from a single medical center in Taiwan. Any NC in the first 30 d post-liver transplantation, and perioperative variables from multiple perspectives were collected and analyzed. The main outcome was a 30-d NC. Generalized additive models were used to detect the non-linear effect of continuous variables on outcome, and to determine cut-off values for categorizing risk. Risk factors were identified using multiple logistic regression analysis. RESULTS: In all, 288 recipients were included, of whom 142 (49.3%) experienced at least one NC, with encephalopathy being the most common 106 (73%). NCs prolonged hospital stay (35.15 ± 43.80 d vs 20.88 ± 13.58 d, P < 0.001). Liver recipients' age < 29 or ≥ 60 years, body mass index < 21.6 or > 27.6 kg/m(2), Child-Pugh class C, history of preoperative hepatoencephalopathy or mental disorders, day 7 tacrolimus level > 8.9 ng/mL, and postoperative intra-abdominal infection were more likely associated with NCs. Novel risk factors for NCs were donor age < 22 or ≥ 40 years, male-to-male gender matching, graft-recipient weight ratio 0.9%-1.9%, and sequence of transplantation between 31 and 174. CONCLUSION: NCs post- liver transplantation occurs because of factors related to recipient, donor, and surgeon. Our results provide a basis of risk stratification for surgeon to minimize neurotoxic factors during transplantation.

Is Metal-On-Metal Total Hip Arthroplasty Associated With Neurotoxicity?

BACKGROUND: Isolated case reports in the literature describe systemic neurologic side effects associated with metal-on-metal (MOM) bearing surfaces, yet the incidence of these effects have not been evaluated beyond individual cases. The purpose of this study was to compare new diagnoses of these side effects described in isolated cases in large patient cohorts of MOM vs metal on polyethylene (MOP). METHODS: We queried the entire Medicare database from 2005 to 2012. Total hip arthroplasty (THA) and bearing surface were determined using International Classification of Diseases, 9th revision procedure codes. Patients with 5-year follow-up were selected. Using International Classification of Diseases, 9th revision codes, we identified new diagnoses of previously reported neurologic side effects: peripheral neuropathy, sensorineural hearing loss, visual impairment, paresthesias, tinnitus, and vertigo. Comorbidities and demographics were collected. Odds ratios, CIs, and P values were calculated. RESULTS: Overall, 29,483 MOM THAs and 23,587 age- and gender-matched MOP THAs were identified. The average Charlson Comorbidity Index was 5 for both groups. MOM and MOP patients had 26 of 30 identical prevalence of Elixhauser-measure comorbidities. There was no statistically significant difference in new diagnoses of any of the side effects at any time point between the 2 groups over 5 years. CONCLUSION: This study represents, to our knowledge, the first longitudinal analysis of systemic neurotoxicity after THA in a large cohort of patients. The results of our study suggest that on the large scale, neurologic side effects previously described do not occur as a common attributable complication. Rather, these cases may be due to individual patient hypersensitivity to metal ions.

Groundwater pesticide levels and the association with Parkinson disease.

It is unclear whether exposure to environmentally relevant levels of pesticides in groundwater is associated with an increased risk of Parkinson disease (PD). The purpose of this study was to examine the relationship between PD and pesticide levels in groundwater. This cross-sectional study included 332 971 Medicare beneficiaries, including 4207 prevalent cases of PD from the 2007 Colorado Medicare Beneficiary Database. Residential pesticide levels were estimated from a spatial model based on 286 well water samples with atrazine, simazine, alachlor, and metolachlor measurements. A logistic regression model with known PD risk factors was used to assess the association between residential groundwater pesticide levels and prevalent PD. We found that for every 1.0 µg/L of pesticide in groundwater, the risk of PD increases by 3% (odds ratio = 1.03; 95% confidence interval: 1.02-1.04) while adjusting for age, race/ethnicity, and gender suggesting that higher age-standardized PD prevalence ratios are associated with increasing levels of pesticides in groundwater.

Chemotherapy-induced polyneuropathy: major agents and assessment by questionnaires.

Chemotherapy-induced polyneuropathy (CIPN) is a common, but underestimated, clinical challenge. Incidence varies depending on many factors that are equally as important as the type of chemotherapeutic agent itself. Moreover, the assessment of CIPN is still uncertain, as several of the most frequently used scales do not rely on a formal neurological evaluation and depend on patients' reports and examiners' interpretations. Therefore, the aim of this MiniReview was to introduce the most common chemotherapies that cause neuropathy, and in addition to this, highlight the most significant differences between the neuropathic pain scales, which are most commonly used for assessing CIPN.

Clinical, laboratory, diagnostic, and histopathologic features of diethylene glycol poisoning--Panama, 2006.

STUDY OBJECTIVE: Diethylene glycol is a toxic industrial solvent responsible for more than 13 mass poisonings since 1937. Little is known about the clinical spectrum, progression, and neurotoxic potential of diethylene glycol-associated disease because of its high mortality and the absence of detailed information in published mass poisoning reports. This incident includes the largest proportion of cases with neurotoxic signs and symptoms. We characterize the features of a diethylene glycol mass poisoning resulting from a contaminated cough syrup distributed in Panama during 2006. METHODS: This was a retrospective chart review and descriptive analysis in a tertiary level, urban health care facility. A case was a person admitted to the Social Security Metropolitan Hospital in Panama City between June 1 and October 22, 2006, with unexplained acute kidney injury and a serum creatinine level of greater than or equal to 2 mg/dL, or unexplained chronic renal failure exacerbation (>2-fold increase in baseline serum creatinine level) and history of implicated cough syrup exposure. Main outcomes and measures were demographic, clinical, laboratory, diagnostic, histopathologic, and mortality data with descriptive statistics. RESULTS: Forty-six patients met inclusion criteria. Twenty-four (52%) were female patients; median age was 67 years (range 25 to 91 years). Patients were admitted with acute kidney injury or a chronic renal failure exacerbation (median serum creatinine level 10.0 mg/dL) a median of 5 days after symptom onset. Forty patients (87%; 95% confidence interval [CI] 74% to 95%) had neurologic signs, including limb (n=31; 77%; 95% CI 62% to 89%) or facial motor weakness (n=27; 68%; 95% CI 51% to 81%). Electrodiagnostics in 21 patients with objective weakness demonstrated a severe sensorimotor peripheral neuropathy (n=19; 90%; 95% CI 70% to 99%). In 14 patients without initial neurologic findings, elevated cerebrospinal fluid protein concentrations without pleocytosis were observed: almost all developed overt neurologic illness (n=13; 93%; 95% CI 66% to 100%). Despite use of intensive care and hemodialysis therapies, 27 (59%) died a median of 19 days (range 2 to 50 days) after presentation. CONCLUSION: A high proportion of patients with diethylene glycol poisoning developed progressive neurologic signs and symptoms in addition to acute kidney injury. Facial or limb weakness with unexplained acute kidney injury should prompt clinicians to consider diethylene glycol poisoning. Elevated cerebrospinal fluid protein concentrations without pleocytosis among diethylene glycol-exposed persons with acute kidney injury may be a predictor for progressive neurologic illness.

Integration of epidemiology and animal neurotoxicity data for risk assessment.

Most human health risk assessments are based on animal studies that can be conducted under conditions where exposure to multiple doses of a single chemical can be controlled. Data from epidemiology studies also provide valuable information about human exposure and response to pesticides. Human studies have the potential of evaluating neurobehavioral and other outcomes that may be more difficult to evaluate in animals. The human data together with animal data can contribute to a weight-of-evidence analysis in the characterization of human health risks. Epidemiology data do, however, pose challenges with respect to characterizing human health risks. Similarly, animal data at high doses or routes of exposure not typical for humans also pose challenges to dose-response evaluations needed for risk assessments. This paper summarizes some of the presentations given at a symposium held at the Xi'an, China, International Neurotoxicology Conference held in June 2011. This symposium brought together scientists from government, industry and academia to discuss approaches to evaluating and conducting animal and human neurotoxicity studies for risk assessment purposes, using the pesticides paraquat and chlorpyrifos as case studies.

Occupational exposure to neurotoxic substances in Asian countries - challenges and approaches.

The fact that a conference on neurotoxicity was held in China triggered the idea to provide an insight into occupational diseases, their development and the approaches to investigate them in Asian countries. A historical review, a meta-analysis, and studies on humans and animals provide impressions on past and current problems. The Korean example showed that each newly introduced industry is accompanied by its own problems as regards occupational diseases. Mercury and carbon disulfide were of importance in the beginning, whereas solvents and manganese became important later. Outbreaks of diseases were important reasons to guide both the public and the governmental attention to prevention and allowed within a relatively short time considerable progress. As the example on the replacement of 2-bromopropane by 1-bromopropane showed, also the introduction of chemicals that are more beneficial for the environment may result in additional occupational risks. A lower mutagenicity of 1-bromopopane was shown to be associated with a greater neurotoxicity in Japanese studies. Although occupational health and diseases are commonly related to adults, child workers exposed to solvents were examined in a Lebanese study. The study started outlining the health hazards in young workers because they might be at a much greater risk due to the not yet completed maturation of their nervous system. That some occupational diseases are not yet a focus of prevention was shown by the study on pesticides. If at all, the serious health consequences resulting from excessive exposure were investigated. Research enabling precautionary actions was not available from the international literature. Despite globalization the knowledge on occupational diseases is not yet "globalized" and each country obviously undergoes its own development triggered by local experiences. Economic development that requires a healthy workforce, but also public interest that challenges governmental regulations further efforts on the prevention of occupational diseases. The paper reflects a summary of the talks presented at the symposium "Occupational Neurotoxicities in Asian Countries" as part of the 11th International Symposium on Neurobehavioral Methods and Effects in Occupational and Environmental Health.

A retrospective cohort study of the association of anesthesia and hernia repair surgery with behavioral and developmental disorders in young children.

Recent animal studies have shown that commonly used anesthetic agents may have serious neurotoxic effects on the developing brain. The purpose of this study was to assess the association between surgery for hernia repair and the risk of behavioral and developmental disorders in young children. We performed a retrospective cohort analysis of children who were enrollees of the New York State Medicaid program. Our analysis involved following a birth cohort of 383 children who underwent inguinal hernia repair during the first 3 years of life, and a sample of 5050 children frequency-matched on age with no history of hernia-repair before age 3. After controlling for age, sex, and complicating birth-related conditions such as low birth weight, children who underwent hernia repair under 3 years of age were more than twice as likely as children in the comparison group to be subsequently diagnosed with a developmental or behavioral disorder (adjusted hazard ratio 2.3, 95% confidence interval 1.3, 4.1). Our findings add to recent evidence of the potential association of surgery and its concurrent exposure to anesthetic agents with neurotoxicity and underscore the need for more rigorous clinical research on the long-term effects of surgery and anesthesia in children.

Prospective assessment of chemotherapy-induced peripheral neuropathy due to weekly paclitaxel in patients with advanced or metastatic breast cancer (CSP-HOR 02 study).

GOALS OF WORK: The aim of this study was to prospectively evaluate chemotherapy-induced peripheral neuropathy (CIPN) using a patient-based instrument, the Patient Neurotoxicity Questionnaire (PNQ) and a physician-based instrument, the National Cancer Institute-Common Toxicity Criteria (NCI-CTC) in patients with advanced or metastatic breast cancer who were treated with weekly paclitaxel. MATERIALS AND METHODS: CIPN symptoms were prospectively assessed in 35 patients using the PNQ, NCI-CTC, and the Functional Assessment of Cancer Therapy (FACT)-Taxane including neurotoxicity component (Ntx) at the baseline, and 8 and 16 weeks after starting chemotherapy. RESULTS: For sensory neuropathy symptoms, the reported incidence of CIPN was significantly increased during active treatment in terms of both the PNQ and NCI-CTC assessments. In contrast, there was a notable increase of patient motor neuropathy symptoms that were elucidated only by the PNQ. The PNQ grades of CIPN were widely distributed in the patient population as compared with the NCI-CTC grades for both sensory and motor neuropathy. The sensory PNQ grade was correlated with sensory NCI-CTC grade (r = 0.58) and Ntx (r = 0.51), and the motor PNQ grade was correlated with Ntx (r = 0.57). CONCLUSIONS: The PNQ appears to be more sensitive and responsive than the NCI-CTC for CIPN; the PNQ appears to have diagnostic validity for evaluating CIPN in patients who are receiving neurotoxic chemotherapy.

Neurobehavioral testing in human risk assessment.

Neurobehavioral tests are being increasingly used in human risk assessment and there is a strong need for guidance. The field of neurobehavioral toxicology has evolved from research which initially focused on using traditional neuropsychological tests to identify "abnormal cases" to include methods used to detect sub-clinical deficits, to further incorporate the use of neurosensory assessment, and to expand testing from occupational populations to vulnerable populations including older adults and children. Even as exposures in the workplace are reduced, they have been increasing in the environment and research on exposure has now expanded to cross the entire lifetime. These neurobehavioral methods are applied in research and the findings used for regulatory purposes to develop preventative action for exposed populations. This paper reflects a summary of the talks presented at the Neurobehavioral Testing in Human Risk Assessment symposium presented at the 11th meeting of the International Neurotoxicology Association.

Biosensor assay of neuropathy target esterase in whole blood as a new approach to OPIDN risk assessment: review of progress.

Organophosphates (OPs) that inhibit neuropathy target esterase (NTE) with subsequent ageing can produce OP-induced delayed neuropathy (OPIDN). NTE inhibition in lymphocytes can be used as a biomarker of exposure to neuropathic OPs. An electrochemical method was developed to assay NTE in whole blood. The high sensitivity of the tyrosinase carbon-paste biosensors for the phenol produced by hydrolysis of the substrate, phenyl valerate, allowed NTE activity to be measured in diluted samples of whole blood, which cannot be done using the standard colorimetric assay. The biosensor was used to establish correlations of NTE inhibitions in blood with that in lymphocytes and brain after dosing hens with a neuropathic OP. The results of further studies demonstrated that whole blood NTE is a reliable biomarker of neuropathic OPs for up to 96 hours after exposure. These validation results suggest that the biosensor NTE assay for whole blood could be developed to measure human exposure to neuropathic OPs as a predictor of OPIDN. The small blood volume required (100 microL), simplicity of sample preparation and rapid analysis times indicate that the biosensor should be useful in biomonitoring and epidemiological studies. The present paper is an overview of our previous and ongoing work in this area.

Integrating epidemiology and toxicology in neurotoxicity risk assessment.

Neurotoxicity risk assessments depend on the best available scientific information, including data from animal toxicity studies, human experimental studies and human epidemiology studies. There are several factors to consider when evaluating the comparability of data from studies. Regarding the epidemiology literature, issues include choice of study design, use of appropriate controls, methods of exposure assessment, subjective or objective evaluation of neurological status, and assessment and statistical control of potential confounding factors, including co-exposure to other agents. Animal experiments must be evaluated regarding factors such as dose level and duration, procedures used to assess neurological or behavioural status, and appropriateness of inference from the animal model to human neurotoxicity. Major factors that may explain apparent differences between animal and human studies include: animal neurological status may be evaluated with different procedures than those used in humans; animal studies may involve shorter exposure durations and higher dose levels; and most animal studies evaluate a single substance whereas humans typically are exposed to multiple agents. The comparability of measured outcomes in animals and humans may be improved by considering functional domains rather than individual test measures. The application of predictive models, weight of evidence considerations and meta-analysis can help evaluate the consistency of outcomes across studies. An appropriate blend of scientific information from toxicology and epidemiology studies is necessary to evaluate potential human risks of exposure to neurotoxic substances.

Assessing the effects of environmental toxicant exposure in developmental epidemiological studies: issues for risk assessment.

Epidemiological studies have been of critical importance to the understanding of the effects of environmental chemical exposure during development on the behavior of infants and children. The ultimate goal of these studies should be to provide information that may be used directly for the protection of public health. The strategies for the assessment endpoints include development of domain-specific tests based on knowledge concerning effects of the chemicals being assessed, or use of standard clinical instruments that sample a range of functions. Discussion of an overall strategy for choice of endpoints would allow more straightforward comparisons across studies. There is increasing recognition of the importance of measuring a number of chemicals relevant to the population under study; however, different investigators make different decisions concerning which and how many chemicals to measure, as well as how to include them in the statistical analysis, particularly when there is a high degree of collinearity. Chemicals that are highly correlated with the "chemical of interest" are sometimes not included in the statistical analysis, resulting in missed opportunity to derive important information from the study. In addition, the shape of the relationship between exposure and effect is usually not explored in epidemiological studies, even though such information is critical for risk assessment. Opportunity for discussion among investigators, statisticians, and risk assessors potentially would result in human developmental toxicity studies being maximally useful for public health decisions.

Visits to physicians after the oxygenation of gasoline in Philadelphia.

During the period between 1992 and 1997, there was an increase in levels of methyl tertiary butyl ether (MTBE) in gasoline in the Philadelphia, Pennsylvania, area. In this study, the authors analyzed billing records from clinical practices that were extensions of the University of Pennsylvania. The authors based their selections on the International Classification of Diseases-9 diagnostic codes, which were determined from (1) previous studies of methyl tertiary butyl ether conducted by the Centers for Disease Control; (2) respiratory symptoms, including asthma and wheezing; and (3) symptoms associated anecdotally with methyl tertiary butyl ether levels in gasoline. The authors normalized all data by the total number of office visits. The incidences of headache, throat irritation, allergic rhinitis, cough, nausea, dizziness, upper respiratory infections, wheezing, otitis media, skin rash, anxiety, insomnia, palpitations, generalized allergy, and malaise were increased during the period studied. Large increases occurred during the winters of 1993-1994 and 1994-1995 (during which there were high levels of MTBE), but not in the preceding summers (during which there were low levels of MTBE). This was especially true for asthma and wheezing. During the summers of 1995, 1996, and 1997, the incidences of the aforementioned symptoms increased greatly.