Plummeting toxic contaminates from water through phycoremediation: Mechanism, influencing factors and future outlook to enhance the capacity of living and non-living algae.

Freshwater habitats hold a unique role in the survival of all living organisms and supply water for drinking, irrigation, and life support activities. In recent decades, due to anthropogenic activities, deterioration in the water quality has been a long-lasting problem and challenge to the scientific fraternity. Although, these freshwater bodies have a bearable intrinsic capacity for pollution load however alarming increase in pollution limits the intrinsic capacities and requires additional technological interventions. The release of secondary pollutants from conventional interventions further needs revisiting the existing methodologies and asking for green interventions. Green interventions such as phycoremediation are natural, eco-friendly, economic, and energy-efficient alternatives and provide additional benefits such as nutrient recovery, biofuel production, and valuable secondary metabolites from polluted freshwater bodies. This systemic review in a nut-shell comprises the recent research insights on phycoremediation, technological implications, and influencing factors, and further discusses the associated mechanisms of metal ions biosorption by living and non-living algae, its advantages, and limitations. Besides, the article explores the possibility of future research prospects for applicability at a field scale that will help in the efficient utilization of resources, and improved ecological and health risks.

Evidence-based clinical practice guideline for the evaluation of potentially malignant disorders in the oral cavity: a report of the American Dental Association

BACKGROUND: An expert panel convened by the American Dental Association (ADA) Council on Scientific Affairs and the Center for Evidence-Based Dentistry conducted a systematic review and formulated clinical recommendations to inform primary care clinicians about the potential use of adjuncts as triage tools for the evaluation of lesions, including potentially malignant disorders (PMDs), in the oral cavity. TYPES OF STUDIES REVIEWED: This is an update of the ADA's 2010 recommendations on the early diagnosis of PMDs and oral squamous cell carcinoma. The authors conducted a systematic search of the literature in MEDLINE and Embase via Ovid and the Cochrane Central Register of Controlled Trials to identify randomized controlled trials and diagnostic test accuracy studies. The authors used the Grading of Recommendations Assessment, Development and Evaluation approach to assess the certainty in the evidence and to move from the evidence to the decisions. RESULTS: The panel formulated 1 good practice statement and 6 clinical recommendations that concluded that no available adjuncts demonstrated sufficient diagnostic test accuracy to support their routine use as triage tools during the evaluation of lesions in the oral cavity. For patients seeking care for suspicious lesions, immediate performance of a biopsy or referral to a specialist remains the single most important recommendation for clinical practice. In exceptional cases, when patients decline a biopsy or live in rural areas with limited access to care, the panel suggested that cytologic testing may be used to initiate the diagnostic process until a biopsy can be performed (conditional recommendation, low-quality evidence). CONCLUSIONS AND PRACTICAL IMPLICATIONS: The authors urge clinicians to remain alert and take diligent action when they identify a PMD. The authors emphasize the need for counseling because patients may delay diagnosis because of anxiety and denial.(AU)

Assessment of background gamma radiation levels using airborne gamma ray spectrometer data over uranium deposits, Cuddapah Basin, India - A comparative study of dose rates estimated by AGRS and PGRS.

The Atomic Minerals Directorate for Exploration and Research (AMD) has conducted high-resolution airborne gamma ray spectrometer (AGRS), magnetometer and time domain electromagnetic (TDEM) surveys for uranium exploration, along the northern margins of Cuddapah Basin. The survey area includes well known uranium deposits such as Lambapur-Peddagattu, Chitrial and Koppunuru. The AGRS data collected for uranium exploration is utilised for estimating the average absorbed rates in air due to radio-elemental (potassium in %, uranium and thorium in ppm) distribution over these known deposit areas. Further, portable gamma ray spectrometer (PGRS) was used to acquire data over two nearby locations one from Lambapur deposit, and the other from known anomalous zone and subsequently average gamma dose rates were estimated. Representative in-situ rock samples were also collected from these two areas and subjected to radio-elemental concentration analysis by gamma ray spectrometer (GRS) in the laboratory and then dose rates were estimated. Analyses of these three sets of results complement one another, thereby providing a comprehensive picture of the radiation environment over these deposits. The average absorbed area wise dose rate level is estimated to be 130 ± 47 nGy h-1 in Lambapur-Peddagattu, 186 ± 77 nGy h-1 in Chitrial and 63 ± 22 nGy h-1 in Koppunuru. The obtained average dose levels are found to be higher than the world average value of 54 nGy h-1. The gamma absorbed dose rates in nGy h-1 were converted to annual effective dose rates in mSv y-1 as proposed by the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). The annual average effective dose rates for the entire surveyed area is 0.12 mSv y-1, which is much lower than the recommended limit of 1 mSv y-1 by International Commission on Radiation protection (ICRP). It may be ascertained here that the present study establishes a reference data set (baseline) in these areas to assess any changes in gamma radiation levels due to mining and milling activities in future.

Correlation of various histopathologic prognostic factors with Nottingham prognostic index and microvessel density in invasive breast carcinoma: A study of 100 cases.

BACKGROUND: Nottingham prognostic index (NPI) is a widely used integrated prognostic variable in patients with breast cancer. NPI has been correlated with tumor size, grade, lymph node stage and patient survival. The present study aimed at evaluating and correlating the various clinical and pathologic features of breast carcinoma with NPI. METHODS: This study included 100 consecutive cases of primary breast carcinoma over a period of 2 years. Demographic data was noted and histomorphological features like tumor size, grade, lymph node involvement, necrosis, vascular invasion etc., were assessed. NPI was calculated as reported in the literature. Immunohistochemical staining for hormone receptors and CD34 (to calculate microvessel density [MVD]) was performed. Statistical analysis was used for correlation. RESULTS: Of the 100 cases, 54% of the tumors were in T2 tumor size category (2-5 cm) and lymph node metastasis in 48% of the cases. NPI ranged from 2.3 to 7.3 with 54% of the cases in the intermediate NPI group (3.41-5.4). The mean MVD was 160.93 (±69.4/mm2). On statistical analysis, tumor size and grade, lymph node stage, mitotic rate, nuclear pleomorphism, necrosis and MVD showed a correlation with NPI (P < 0.05). CONCLUSION: NPI is an important and useful prognostic indicator for breast cancer patients, which shows the correlation with other histomorphological prognostic features as well.

Palliative weekly chemotherapy along with cetuximab in recurrent and metastatic head and neck cancers: a retrospective analysis.

BACKGROUND: This study was undertaken to report the results of weekly combination chemotherapy with cetuximab in recurrent/metastatic head and neck squamous cell carcinoma (R/M SCCHN). MATERIALS AND METHODS: Retrospective analysis of 35 R/M SCCHN patients who received cetuximab with weekly paclitaxel and platin (cisplatin/carboplatin) from SCCHN August 2006 to October 2008 at our Institute was performed. RESULTS: Thirty-five patients (33 [94.3%] males and 2 [5.7%] females) received the planned weekly chemotherapy protocol. Median age of these patients was 52 years. Of the SCCHN 32 evaluable patients, 25 patients showed symptomatic improvement and 7 showed no improvement. Radiological responses using RECIST criteria reported CR in 1 patient (3.1%), PR in 17 patients (53.1%), and SD in 6 patients (18.8%). The remaining six patients demonstrated disease progression while two could not be assessed. Median overall survival (OS) was 8.016 months (95% CI; 6.572--9.461) and median PFS was 5.782 months (95% CI; 4.521--7.044). The major chemotherapy-related grades 2 and 3 toxicity recorded was cetuximab-induced rash reported in 24 patients. No treatment-related death within 30 days was observed. CONCLUSION: Cetuximab with weekly combination chemotherapy (Paclitaxel + Platinum compound) has shown promise, demonstrating comparable response and outcomes with acceptable toxicity in R/M SCCHN patients.

Melanotic neuroectodermal tumor of infancy: discussion of a case and a review of the imaging findings.

Melanotic neuroectodermal tumor of infancy (MNTI) is an uncommon melanin-containing mesenchymal tumor of neural crest origin. What make this tumor unique and interesting is its characteristic predilection for anterior maxilla (premaxilla) and the presence of pigment melanin which gives the tumor distinct clinicopathological, immunohistochemical, ultrastructural and imaging features. Although first described almost a century ago, to the authors' knowledge, only a few hundred cases of MNTI have been reported worldwide in the English medical literature. The pool of documented radiological findings is even more sparse as not more than a dozen cases could be abstracted from an Internet search of the radiology literature. We document a case of MNTI and describe the imaging findings with intent to contribute to its small but accruing radiological data.

A novel dodecapeptide from a combinatorial synthetic library exhibits potent antifungal activity and synergy with standard antimycotic agents.

There has been a marked expansion in the discovery of new antifungal peptides. This paper describes a novel dodecapeptide, H-Arg-Trp-Trp-Arg-D-Trp-D-Phe-Ile-D-Phe-His-Trp-Arg-Trp-NH(2), derived from a previously described nonapeptide and synthesized by the combinatorial approach. Further, interaction of this peptide with antifungals such as amphotericin B, flucytosine and fluconazole was studied by checkerboard analysis and time-kill assay to obtain the dynamic picture with respect to time. The best synergistic activity was observed with a combination of peptide and fluconazole, followed by peptide and flucytosine.

Immunolocalization of secretory proteins of Aspergillus fumigatus using monospecific polyclonal antibodies in a murine model.

The incidence of life-threatening mycoses caused by opportunistic fungi has increased dramatically in recent years with members of the genera Candida and Aspergillus being the most commonly encountered species. Prompt initiation of antifungal therapy for good prognosis of such cases is highly dependent on accurate diagnosis. The potential of metabolic antigens in the diagnosis of aspergillosis was investigated in the present study. Two proteins of 18 and 70 kDa were identified with success rate of 35% and 60% respectively based on their reactivity with patient sera of clinically diagnosed cases of aspergillosis. The antibodies raised against 70 and 18 kDa proteins in rabbits were found to be useful in detection of A. fumigatus in the kidneys of a mouse model of aspergillosis.

Synthesis of 4-hydroxy-1-methylindole and benzo[b]thiophen-4-ol based unnatural flavonoids as new class of antimicrobial agents.

Synthesis of nitrogen and sulfur heterocyclic mimics of furanoflavonoids have been achieved for the first time. Synthesized flavonoid alkaloids and thiophenyl flavonoids have been screened for antifungal and antibacterial activities. All the test compounds barring 25 exhibited antifungal activity. The compound 19 was the best and showed comparable MICs to the known compound karanjin. Compounds 5, 12, 14 and 22 also showed comparable MIC to karanjin.

Synthesis of galactopyranosyl amino alcohols as a new class of antitubercular and antifungal agents.

The galactopyranosyl amino alcohols (3-16) were synthesised by regioselective oxirane ring opening of compound 2 with variety of amines and screened for antitubercular and antifungal activities. One of the compounds (16) showed potent activity against Mycobacterium tuberculosis H37 Rv in vitro and also displayed activity in MDR TB. The compound (16) was found to be superior to ethambutol clinically used anti TB drug in in vitro screen.

A fatality caused by accidental production of hydrogen sulfide.

A 55-year-old male Caucasian truck driver was dead at the scene after breathing hydrogen sulfide (H(2)S) produced by an accidental transfer of sodium hydrogen sulfide (NaHS) from a tanker truck to a tank containing 4% sulfuric acid (H(2)SO(4)) and iron(II) sulfate (FeSO(4)). Autopsy of the decedent's body revealed pulmonary edema and passive congestion in lungs, spleen, kidneys, and adrenal glands. Postmortem biological samples were analyzed for carbon monoxide, cyanide, ethanol, and drugs. Since a potential exposure to H(2)S was involved, blood was also analyzed for sulfide (S(2-)). The analysis entailed isolating S(2-) from blood as H(2)S using 0.5M H(3)PO(4), trapping the gas in 0.1M NaOH, and determining the electromotive force using a sulfide ion specific electrode. Acetaminophen at a concentration of 14.3 microg/ml was found in blood, and metoprolol was detected in the blood, liver, and kidney samples. The blood S(2-) level was determined to be 1.68 microg/ml. It is concluded that the cause of death was H(2)S poisoning associated with a hazardous material accident in an industrial situation.

Blood carbon monoxide and hydrogen cyanide concentrations in the fatalities of fire and non-fire associated civil aviation accidents, 1991-1998.

Blood samples submitted to the Civil Aeromedical Institute (CAMI) from aviation accident fatalities are analyzed for carbon monoxide (CO), as carboxyhemoglobin (COHb), and hydrogen cyanide, as cyanide (CN(-)). These analyses are performed to establish possible exposure of victims to smoke from in-flight/post-crash fires or to CO from faulty exhaust/heating systems. The presence of both gases in blood would suggest that the victim was alive and inhaled smoke. If only COHb is elevated, the accident (or a death) could be the result of CO contamination of the interior. Information pertaining to blood levels of these gases in aviation fatalities, in relation to the associated accidents, is scattered or not available, particularly with regard to toxicity. Therefore, considering that COHb> or =10% and CN(-)> or =0.25 microg/ml are sufficient to produce some degree of toxicological effects, the necessary information was extracted from the CAMI database. Samples from 3857 fatalities of 2837 aviation accidents, occurring during 1991-1998, were received; 1012 accidents, encompassing 1571 (41%) fatalities, were fire associated, whereas 1820 accidents were non-fire related. The remaining five accidents were of unknown fire status. There were fewer fire related fatalities and associated accidents in the (COHb> or =10% and CN(-)> or =0.25 microg/ml) category than that in the (COHb<10% and CN(-)<0.25 microg/ml) category. No in-flight fire was documented in the former category, but in-flight fires were reported in 14 accidents (18 fatalities) in the latter category. No non-fire accident fatality was found wherein levels of both gases were determined to be at or above the stated levels. There were 15 non-fire accidents with 17 fatalities wherein only COHb (10-69%) was elevated. The present study suggests that aviation fire accidents/fatalities were fewer than aviation non-fire accidents/fatalities and confirms that aviation accidents related to in-flight fires and CO-contaminated interiors are rare.

Abnormal glucose levels found in transportation accidents.

BACKGROUND: The Federal Aviation Administration's Office of Aerospace Medicine is responsible for the certification of pilots with diabetic conditions. The present study evaluated the use of postmortem vitreous humor and urine glucose levels in transportation accident fatalities as indicators of potentially incapacitating medical conditions or performance impairment. METHODS: Vitreous humor and/or urine from 192 accident fatalities were analyzed for glucose using a hexokinase method. Cases with values below the lower limit of detection (10 mg x dl(-1)) and above 3 standard deviations (SD) from the mean were not included in the final statistics. All cases more than 5 SD above the mean were deemed abnormal and a full case history was evaluated based on the available medical history. RESULTS: The mean vitreous humor glucose concentration was 30+/-21 mg x dl(-1) (N=98), while it was 27+/-16 mg x dl(-1) in urine (N=127). Of the 192 cases, 9 were identified as having abnormal glucose levels. Abnormal glucose levels were found in 5 of the 8 cases with a known diabetic condition. Glycosuria or low renal threshold was reported in 2 fatal pilots; 1 of these pilots had an abnormal glucose level. CONCLUSIONS: Hyperglycemia can be established from the vitreous humor and urine glucose levels. All of the abnormal glucose cases detected were previously identified during the medical certification process or had a medical reason for the abnormal level. Elevated vitreous humor and urine glucose levels have proven useful in identifying individuals with a pre-existing diabetic condition that might have been a factor in the accident.

Formation of an interfering substance, 3,4-dimethyl-5-phenyl-1,3-oxazolidine, during a pseudoephedrine urinalysis.

During fatal aviation accident investigations, biosamples from the victims are submitted to the FAA Civil Aeromedical Institute (CAMI) for drug analysis. In the process of one such analysis by CAMI, an unknown substance was found in a urine sample. Simultaneous screening by thin layer chromatography (TLC) and gas chromatography/FID (GC/FID) suggested the presence of pseudoephedrine. A subsequent routine confirmation analysis of a separate urine aliquot by GC Fourier transform infrared (GC/FTIR) and GC mass spectrometry (GC/MS) indicated that the retention times of the unknown substance matched with those of pseudoephedrine. However, its infrared and mass spectra were different--the -OH and -NH groups were missing, a C-O-C group was present, and the molar mass was 12 atomic mass units (amu) more than that of pseudoephedrine. A subsequent literature search suggested that ephedrine-like amines react with aldehydes to form oxazolidines. Therefore, the 12-amu increase could be accounted for by condensation of pseudoephedrine with formaldehyde. Since this aldehyde is present in various grades of methanol and ethyl acetate, and these solvents were used during the solid-phase extraction, 3,4-dimethyl-5-phenyl-1,3-oxazolidine was synthesized by using (+)-pseudoephedrine HCl and formaldehyde. The analytical findings of the synthesized compound were consistent with those of the unknown interfering substance, confirming that it was the oxazolidine. Aldehyde contaminants in solvents or specimens can transform drugs of interest and may result in misidentification of a compound originally present in specimens. Therefore, chemicals used in analyses should be of the highest available purity, and a multi-analytical approach should be adopted to maintain a high degree of quality assurance.

The FAA's postmortem forensic toxicology self-evaluated proficiency test program: the first seven years.

Existing proficiency-testing (PT) programs do not address the complexity of postmortem forensic toxicology. These programs do not include decomposed samples and solid tissues. Therefore, the Federal Aviation Administration in July 1991 started such a needed PT program. This program is used to: (i) professionally develop and maintain technical currency on a voluntary, interlaboratory, and self-evaluation basis, and (ii) quantifiably assess methods in the absence and presence of interfering substances. There are currently about 30 laboratories in the program. Functioning under various governmental/non-governmental agencies and academic institutions, these laboratories represent a broad cross-section of the country. PT samples are distributed quarterly, and result summaries are sent to the participants, while maintaining their anonymity. Since the inception of the program, 28 PT samples encompassing whole blood, plasma, urine, kidney, or liver, with (or without) drugs, metabolites, and common chemicals (nicotine, caffeine, beta-phenylethylamine, etc.) have been analyzed by the participants. Analytical findings were generally consistent with the anticipated values, but they were dependent on the nature and conditions of the specimens and types of the added analytes. Some incidences of false positives of concern were noted, as well. This PT program is one of the few programs recommended by the American Board of Forensic Toxicology in which laboratories may participate for their accreditation by the Board. It is anticipated that this PT program will continue to play a critical part in supporting the quality assurance/quality control (QA/QC) component of forensic toxicology, thereby enhancing operational performance.

Aspiration vs nonaspiration technique of cytodiagnosis--a critical evaluation in 160 cases.

The two sampling techniques were studied in 160 randomly selected cases of superficial swellings in various sites of the body. They were sampled by fine needle aspiration (FNA) and by non-aspiration (NA) (a needle without application of aspiration pressure). Cell samples were cytologically assessed and critically evaluated using five objective parameters. Contamination with blood was more in lymphnode, thyroid and liver lesions in aspiration smears than NA smears and values were statistically significant. Similarly when compared for the degree of cellular trauma and cellular degeneration statistically significant better results were obtained by nonaspiration technique for lymphnode lesions. Regarding amount of cellular material obtained by FNA, statistical significant better results were found for breast lesions only. Statistically significant better maintenance of architecture was observed only for thyroid lesions by NA technique. Better average scores were observed by NA technique for lymphnode and thyroid only. Categorizing all the smears obtained by FNA & NA on the basis of their scores according to predetermined criteria, greater number of diagnostically adequate specimens were obtained by FNA than by NA but the number of diagnostically superior specimens obtained by NA technique was found to be more than that by FNA. The difference was found to be statistically significant. However the number of inadequate smears was also more by NA technique than by FNA technique.

Prevalence of chlorpheniramine in aviation accident pilot fatalities, 1991-1996.

BACKGROUND: Chlorpheniramine is known to cause drowsiness, and this side effect has a potential to impair performance and could be a factor in accidents. METHODS: Therefore, to establish the prevalence of this drug in pilot fatalities of aviation accidents, a postmortem toxicology database--maintained at the Civil Aeromedical Institute--was examined for the presence of chlorpheniramine in the fatalities, occurred during 1991-1996. RESULTS: There were 47 (2.2%) accidents involving chlorpheniramine. Of these, 16 had only chlorpheniramine at 109 ng.ml-1 (n = 4) in blood and 1412 ng.g-1 (n = 12) in liver. Other drugs were also present in the remaining 31 cases, wherein chlorpheniramine concentrations were 93 ng.ml-1 (n = 18) in blood and 747 ng.g-1 (n = 12) in liver. Ninety-five percent of all quantitated blood values were at or above the therapeutic level (10 ng.ml-1), giving a 100 ng.ml-1 (n = 21) mean blood value. The drug's mean liver concentration from all cases was 1080 ng.g-1 (n = 24). The average blood value was approximately 10 times higher than the therapeutic value. CONCLUSIONS: The presence of other drugs did not appear to significantly alter the blood chlorpheniramine level, but no such correlation could be established with the hepatic value. The approximate 10-fold increase in the liver concentration was consistent with the general trend of drug distribution in the hepatic compartment. However, the contribution of postmortem redistribution of the drug to alter its concentration cannot be entirely ruled out. This study suggests that chlorpheniramine was present in some aviation fatalities at levels higher than therapeutic levels.

Genotyping for DQA1 and PM loci in urine using PCR-based amplification: effects of sample volume, storage temperature, preservatives, and aging on DNA extraction and typing.

Urine is often the sample of choice for drug screening in aviation/general forensic toxicology and in workplace drug testing. In some instances, the origin of the submitted samples may be challenged because of the medicolegal and socioeconomic consequences of a positive drug test. Methods for individualization of biological samples have reached a new boundary with the application of the polymerase chain reaction (PCR) in DNA profiling, but a successful characterization of the urine specimens depends on the quantity and quality of DNA present in the samples. Therefore, the present study investigated the influence of storage conditions, sample volume, concentration modes, extraction procedures, and chemical preservations on the quantity of DNA recovered, as well as the success rate of PCR-based genotyping for DQA1 and PM loci in urine. Urine specimens from male and female volunteers were divided and stored at various temperatures for up to 30 days. The results suggested that sample purification by dialfiltration, using 3000-100,000 molecular weight cut-off filters, did not enhance DNA recovery and typing rate as compared with simple centrifugation procedures. Extraction of urinary DNA by the organic method and by the resin method gave comparable typing results. Larger sample volume yielded a higher amount of DNA, but the typing rates were not affected for sample volumes between 1 and 5 ml. The quantifiable amounts of DNA present were found to be greater in female (14-200 ng/ml) than in male (4-60 ng/ml) samples and decreased with the elapsed time under both room temperature (RT) and frozen storage. Typing of the male samples also demonstrated that RT storage samples produced significantly higher success rates than that of frozen samples, while there was only marginal difference in the DNA typing rates among the conditions tested using female samples. Successful assignment of DQA1 + PM genotype was achieved for all samples of fresh urine, independent of gender, starting sample volume, or concentration method. Preservation by 0.25% sodium azide was acceptable for sample storage at 4 degrees C during a period of 30 days. For longer storage duration, freezing at -70 degrees C may be more appropriate. Thus, the applicability of the DQA1 + PM typing was clearly demonstrated for individualization of urine samples.

PCR-based identification of postmortem microbial contaminants--a preliminary study.

Investigation of postmortem blood can reveal the presence of significant ethanol levels. However, in some instances it cannot easily be determined if the source of ethanol is from ingestion or from postmortem endogenous fermentation by contaminating microbes. Described here is a robust polymerase chain reaction (PCR)-based method for detecting the presence of common ethanol producing microbial contaminants in human blood. A set of DNA primers were designed for use in PCR to amplify and detect the genomic DNA from humans and three test microorganisms Escherichia coli, Proteus vulgaris, and Candida albicans. A rapid and reproducible protocol was developed for isolating genomic DNA from mixed human blood-microorganism samples that yields a suitable template for PCR. The organism-specific primer pairs can detect the presence of the target microorganisms in human blood at concentrations as low as 10 colony forming units/mL. The PCR products readily can be detected after agarose gel electrophoresis. This method provides an additional means of rapidly identifying microbial contaminants in postmortem blood samples.

Melatonin: aeromedical, toxicopharmacological, and analytical aspects.

Melatonin, a pineal hormone present in the blood of humans and other species, has a distinct diurnal variation in its biosynthesis and, therefore, in its concentration. This variation has suggested the possibility of a regulatory function in day/night-dependent physiological processes such as sleep and has led scientists to explore the effects of administered melatonin on the modulation of circadian rhythms. For the self-treatment of sleep disorders and other benefits, melatonin use has been extolled to the extent that 20 million new consumers were added to the U.S. retail market in 1995. Its principal aeromedical application has been in the experimental treatment of jet-lag effects. For aircraft passengers, melatonin administration at destination bedtime appears to improve sleep quality and to decrease the time required to reestablish normal circadian rhythms. For international aircrews that travel through multiple time zones without time to adapt to new environments, taking melatonin before arriving home may further impair already disturbed circadian rhythms. Its use to adjust to shiftwork changes by air traffic controllers, aircraft maintenance workers, and support personnel is even more controversial. Limited studies suggest that giving this hormone to shift workers should be done only under controlled conditions and that taking it at the wrong time may actually impair job performance. Because of its possible interaction with certain medications and the changes in its concentrations observed in some clinical conditions, the practitioner must exercise caution during the medical certification of airmen. The variations in the concentration of melatonin can be effectively determined by radioimmunoassay, high-performance liquid chromatography, and gas chromatography-mass spectroscopy analytical techniques. These techniques are capable of measuring the human daytime (10 pg/mL) and nighttime (30-120 pg/mL) melatonin in plasma/serum. Melatonin measurements in victims of accidental death may allow forensic scientists and accident investigators to use the relationship between its concentration and the time of day when death occurred. The most accurate estimations of the time of death result from analysis of melatonin content of the whole pineal body, whereas less accurate estimates are obtained from serum and urine analyses. Pineal levels of melatonin are unlikely to be altered by exogenous melatonin, but its blood and urine levels would change. High blood levels in a daytime crash victim would suggest exogenous supplementation. The possible interfering effects of postmortem biochemical processes on melatonin concentrations in whole blood and in other tissues are not well understood, and there is a need for the continuing research into melatonin's chronobiological properties to define its proper applications and limitations. The indiscriminate use of melatonin by aviation professionals may pose unacceptable safety risks for air travel.