Perfluorooctane sulfonate and perfluorooctanoic acid in surgical thyroid specimens of patients with thyroid diseases

BACKGROUND

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are ubiquitous compounds that may act as endocrine disruptors, neurotoxic agents, and fetal development perturbing substances and may also be carcinogenic, as recently demonstrated in experimental animal models. There is little information on the potential for these compounds to affect the thyroid. Therefore, this study was performed to measure the intrathyroidal levels of PFOA and PFOS in surgical specimens of thyroid glands and to determine if there was a relationship between the concentrations of these substances and the clinical, biochemical, and histologic phenotype of the patients from whom the thyroids were obtained. We also sought to determine if there was a relationship between tissue and serum levels of both PFOA and PFOS.

METHODS

PFOA and PFOS were measured in 28 patients undergoing thyroid surgery for benign (15 multinodular goiters and 7 Graves' disease) and malignant (5 papillary and 1 follicular carcinoma) thyroid disorders.

RESULTS

PFOA and PFOS were detectable in all surgical specimens of thyroid tissue. Their median concentrations were 2.0 ng/g (range = 0.4-4.6 ng/g) and 5.3 ng/g (range = 2.1-44.7), respectively. Intrathyroidal concentrations of PFOA and PFOS were similar in the thyroids of patients with thyroid diseases as in thyroid glands obtained at autopsy. There was no relationship between the intrathyroidal concentrations of either PFOA or PFOS and the underlying thyroid disease. A significant correlation between the serum and the tissue levels of PFOS was found in all patients. The serum concentrations of PFOA and PFOS were significantly higher than those in the correspondent surgical specimens.

CONCLUSIONS

These observations do not support the view that PFOA and PFOS are actively concentrated in the thyroid. PFOA and PFOS, however, are both found in surgical and autopsy thyroid specimens. Therefore, further studies to determine if they have disrupting effects in thyroid cells or tissue, and studies to compare populations with and without these compounds in their thyroid glands, are important.

[The new methodology to produce instruments for updating occupational physician proposed by Italian Society of Occupational Medicine and Industrial Hygiene (SIMLII)]

Starting from the experience of last five years, during which 24 guide liens about the most important aspects of Occupational Physician activity have been produced, the Italian Society of Occupational Medicine and Industrial Hygiene (SIMLII) delegated a specific working group for updating the methodology to be adopted for guide lines and other instruments for improving and standardizing the current activity in our professional field. SIMLII produced in the context of the specific Education and Accreditation Programme for occupational physicians prepared from 2002 25 guide lines or other informative instruments on the most important and controversial themes in which our discipline is involved. They were considered and treated to meet the need to improve and standardise activities and to modify the current approach of occupational physicians and aimed not only at improving the effectiveness of preventive actions but also at constantly adopting rigorous methodologies based where possible on evidence based or on consensus procedures. The Directive of SIMLII was firmly convinced about the opportunity-necessity to critically evaluate the experience carried out during the last years, at the light of the National Program for Guide Lines edited By Italian National Health Institute since 2002 and which concerns preparation, dissemination, updating, implementation of guide lines in Medicine. The guide lines were defined as rational critical effective aid addressed to professionals and patients for health services organization. Relevant was the new Framework Act for the occupational safety and health (Decreto legislativo 81/08) too signed by the President of the Italian Republic on April 9, 2008, which for the first time includes and defines in a legislative act the different possible instruments (technical normative, good practices, guide lines). In this paper we present the new methodology defined by our Society for producing the different kind of instruments such as guide lines, consensus conference reports, technology assessments, good practices statements guide lines focusing as the main aspects those related to definitions, argument choice, working group and coordinator identification, producing methods, evidence evaluation, grading, quality evaluation using AGREE method, dissemination procedure, the conflict of interest and the possible use for distance formation procedure focusing the recommendations that take a practical-applicative approach.

[The active search for occupational cancers]

The active search for occupational neoplasms has been implemented only in Italy. This search can be carried out with two modalities: the in-hospital face-to-face interview of selected cancer cases, and the linkage of available information (OCCAM). Both were supported by a special project on occupational carcinogenesis of the Lombardy Region. The active search for occupational neoplasms is a moderate-cost activity and is important for the safeguard of the workforce and of the population as a whole.

[E-learning and occupational medicine: results of one experience in Italy]

In Italy, there is at present a certain drive in order to make e-learning for Continuous Medical Education (CME) to take off, even though a normative framework for distance CME has not been completely defined yet. This paper describes the phases of course supply and usage of an e-learning system in the occupational medicine area in Italy. The system provides 10 courses for occupational physicians and one course for nurses, physiotherapists and occupational physiotherapists. During the span of time of 11 months, 2034 users have registered to the website and 1804 of them enrolled themselves into at least one course, for a total number of 5183 course enrolments, with a mean number of course enrolments per person of about 3, and 3710 courses were successfully concluded. This study points out on one hand a wide request for this kind of educational sessions, and on the other hand good results in terms of knowledge acquisition. Since the present experimental project was aimed at contributing to the definition of the normative framework for distance education for CME, it can be expected that e-learning for CME in Italy will get off the ground in the near future.

Usage and effectiveness of e-learning courses for continuous medical education

The paper describes the results of an e-learning experimental project for Continuous Medical Education (CME) in Occupational Medicine in terms of: extent of the e-learning courses usage by the healthcare personnel, knowledge acquisition and satisfaction. 11 courses have been available for 11 months during which 2,034 users all over Italy enrolled in 5,183 courses with a success percentage of 72% and a significant difference between test scores performed before and after attending the e-learning courses. Also user's satisfaction, inspected through a questionnaire, has provided good results. Starting from the experience reported, the authors are confident that e-learning will gain ground and evolve as an effective and appreciated educational mean for CME.

Preliminary evaluation of an e-learning course for healthcare personnel

Preliminary evaluation of an e-learning system for nurses and physiotherapists is presented. The results lead to positive conclusions, but traditional paper-based materials still play an important role in learning activity.

[Usability study of an e-learning system for CME in occupational medicine: preparatory analysis and remedial actions]

This paper describes the activities carried out in order to make an e-learning system for CME be a good tool in terms of usability. The following steps are described:--the needs analysis of the potential users;--the prototype of the e-learning system that has been set up;--the usability evaluation of the prototype by a sample often users before and after the implementation of the identified remedial actions. The obtained results support the hypothesis of an effective usage of the system in the near future. The follow-up of real users' usage, through the tracing facilities of the e-learning platform, will confirm or reject our hypothesis.

[Gene expression and environmental exposure to xenobiotics: overview and applications]

Industrial chemicals, pesticides, pharmaceuticals, foods, heavy metals, air pollutants, and naturally occurring substances, are an integral part of our daily lives. Environmental exposure can induce changes in gene regulation associated with human diseases. A new discipline of toxicology is "predictive toxicology" that defines the relationship between the structure and activity of the genome and the adverse biological effects of exogenous agents. Toxicogenomic technologies allow complete assessment of the functional activity of biochemical pathways, and of the structural genetic (sequence) differences among individuals (polymorphisms), that were previously unattainable. Microarray technology provides the means to study multiple pathways and mechanisms at concurrent times. Gene expression is a sensitive indicator of toxicant exposure, disease state, and cellular metabolism and thus represents a way of characterising how cells and organisms adapt to changes in the external environment. The application of these technologies to toxicology can lead us into a new era when genotypes and toxicant-induced genome expression, proteins, and metabolite patterns can be used to screen compounds for hazard identification, to monitor individual exposure to toxicants, to track cellular responses to different doses, to assess mechanisms of action, and to predict individual variability in sensitivity to toxicants and potential ways to improve risk assessment.

[Work integration of impaired workers in a type-B social cooperative]

This research aims to evaluate job occupation results of impaired workers in a type-B social cooperative, taking into consideration not only specific occupational risks' analysis and assessment, but also organisational, relational and psycho-social matters essential for their stable job occupation. The impaired workers involved were all those hired by a type-B social cooperative from Jan 1999 until Dec 2007, ie. 16 workers (M 8, F 8), equal to 40% of employees' total number. Every impaired worker has been submitted to preventive health surveillance in order to evaluate the degree of disability and residual job ability in relation to the job tasks suitable for him/her. In order to find available tasks which can be performed by disadvantaged workers, the personnel chart has been analyzed, and 10 of the 16 workers (equal to 62.5%) have been considered fit for the specific task without limitations. The other 6 (37.5%) have been considered capable of the specific task with limitations and/or prescriptions, and for 2 of them (12.5%) a tutorial supervision prescription was also necessary. Among those 6 workers with limitations and/or prescriptions, 4 were psychologically impaired (67%) and 2 were physically impaired (37%). The situation of these 16 impaired workers has been periodically verified and followed up for 8 years. Not only have the fifteen workers continued to perform the task initially considered suitable for their health status, but for some of them (5 workers), an increase in job performance, in both complexity and shift duration, has been observed. Moreover, with the only exception of a psychologically impaired worker who did alternate between good comfort times and occasional disease acute phases, all other workers have shown good and stable gains in psychological and physical health conditions, performing requested tasks not only with efficiency, but also with commitment and motivation. All workers have shown a remarkable improvement in their ability to form relationships, mainly within the work environment amongst colleagues and supervisors, but also in a social and family environment. A special mention is deserved in the case of the only worker hired in our research who left the cooperative after many years of work activity where, after having attended specific professional courses, steadily and successfully joined a company still in the social field but not exclusively dedicated to impaired workers. It may be observed that when one faces the work integration of impaired workers, the usual risk evaluation processes cannot be enough for the reason that these workers, due to their 'disability', find themselves in hypersusceptible conditions in respect to occupational risk factors which are generally acceptable for the other workers. In risk assessment it is therefore necessary to perform an accurate and all-round study in every aspect of the job duty, even around those considered irrelevant which, as a result, may show to be unsuitable to the worker's health status or might alter his/her often precarious psychological-physical condition. In conclusion, in the risk assessment process used prior to the work integration of impaired workers considered by our research, the organisational, relational and psycho-social aspects of work activity have often played a primary role in respect to traditional risk factors usually monitored and evaluated.

Saliva as an analytical tool to measure occupational exposure to toluene

OBJECTIVE

To describe a sensitive and rapid method for the determination of toluene in saliva. Biomonitoring of toluene exposure is commonly performed by determination of urinary hippuric acid, o-cresol or toluene itself. The analysis of blood toluene has been verified as another method for biomonitoring. However, drawing blood is invasive and can often not be performed at the workplace for hygienic reasons. Sampling of saliva may be non-invasive, easy to perform and a viable alternative for biomonitoring in the workplace.

METHODS

We measured the solvent concentration in saliva specimens of 5 healthy volunteers studied in the laboratory and a group of 36 workers exposed to toluene in the synthetic leather industry. Saliva was collected into Salivette (Sarstedt, Germany) devices by sterile cotton rolls placed in the mouth and then squeezed into pre-weighted vials. Environmental toluene was collected for the duration of a work-shift by Radiello (FSM, Italy) passive samplers. Toluene in urine and saliva (head space analysis) and in environmental samples was measured by GC-MS.

RESULTS

Environmental toluene levels ranged from 0.22 to 57.20 mg/m(3), while the concentrations of the solvent in saliva and urine ranged from 0.12 to 18.30 microg/L, and from 0.47 to 26.64 microg/L, respectively. The correlation coefficients (r) between biological and environmental levels of toluene were 0.77 and 0.93, respectively, for saliva and urine samples.

CONCLUSION

This preliminary study suggests that saliva may offer many advantages over 'classical' biological fluids such as blood as it is readily accessible and collectible: therefore saliva toluene may be considered as a possible biomarker of exposure to toluene.

[Characteristics, use and toxicity of fluorochemicals: review of the literature]

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are perfluorinated surfactants used to produce polymers and telomers whose carbon chain can be differently long. Polytetrafluoroethylene (PTFE), namely Teflon, is the chief fluoropolymer and it has been widely utilised over the last decades and all over the world. Indeed, its particular physical and chemical properties make it difficult to replace this substance in several industries (textile, paper, chemical, fire-fighting foam industry). Perfluoroalkyl-compounds may be considered ubiquitous and, in particular, it has been shown that PFOS may be concentrated in the food chain. Concerns about possible toxic effects of these chemicals date back to seventies, but only in 2000 the Environmental Protection Agency (EPA) stated PFOA and PFOS withdrawal to avoid environmental pollution. In 2002 the Organisation for Economic Co-operation and Development reported that these substances are bio-persistent, tend to accumulate in different tissues of living organisms and are toxic to mammalians. In 2006 EPA established that every PFOA emission will be eliminated not later than 2015. Actually, health effects of perfluoroalkyl-compounds on humans remain controversial, in spite of a number of experimental and epidemiological studies. Research focuses on possible endocrine disruption, thyroid and liver carcinogenicity, and development alteration. Our article reviews the main studies concerning PFOS and PFOA industrial and environmental toxicology.

[In-progress matrix for occupational cancer recognition]

BACKGROUND

In Italy only a small proportion of all cancers is reported to the national labour insurance board and recognized as having an occupational origin. Cancers with a lower etiological fraction such as lung or bladder cancer have a lower rate of recognition than mesotheliomas or sino-nasal tumours either because of a lack of information obtained via specific occupational anamnesis or because knowledge concerning occupational carcinogens is still uncertain.

OBJECTIVES

To interpret findings and advance new working hypotheses, within the framework of an occupational monitoring survey project (OCCAM) we performed an extensive bibliographical search in the scientific literature on occupational cancer.

METHODS AND RESULTS

We built an on-line "literature matrix" (www.occam.it) containing positive" results from 685 cohort, case-control and cross-sectional epidemiological studies on occupational cancer, from which 1870 citations were obtained describing risk increases by type of cancer and industry. Production cycles or type of industry (iron foundry, leather and shoe manufacturing, etc.) constitute one axis of the matrix and the other consists of type of cancer by site.

CONCLUSIONS

This tool is not only useful for interpretation of evidence arising from occupational cancer surveys but was also intended to be a fast and easy-to-use working tool for occupational physicians, general practitioners and many other specialists to investigate and ascertain the possible occupational origin of a cancer case.

[Validity of urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) as biomarker of exposure to very low concentrations of carbon disulphide: preliminary results]

The possibility to use urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) as biomarker of occupational exposure to very low doses of carbon disulphide (CS2) was evaluated preliminarily in 10 workers employed in a chemical plant where rubber vulcanization accelerators are produced, and in 10 workers, residents in the same geographical area and not occupationally exposed to CS2 and dithiocarbamates (DTC). Exposure to airborne CS2 was assessed, only for exposed workers, by both personal and area samplers. For the determination of TTCA, a spot urine sample was collected for each worker, exposed and non exposed, at the end of work-shift. A questionnaire probing lifestyle and dietary habits and non occupational exposure to CS2 and DTC was administered to all workers involved in the study. Environmental exposure to CS2 in 2007 ranged between 0.21 mg/m3 and 0.73 mg/m3 for personal sampling, and between 0.23 mg/m3 and 0.41 mg/m3 for area sampling. Urinary TTCA levels resulted very low and did not show any significant difference between exposed (Median: 10.8 microg/g creat; Range: 6.1-26.4 microg/g creat) and non exposed workers (Median: 9.3 microg/g creat; Range: 3.0-33.0 microg/g creat), while higher, but not significant concentrations of TTCA were observed in smokers than in non smokers (p = 0.09). No correlation was found between urinary TTCA levels and environmental exposure to CS2, age, body mass index, smoking and dietary habits. In conclusion, the low sensibility and specificity in the assessment of occupational exposure to low doses of CS2 in workers compared to general population subjects, makes urinary TTCA a biomarker with a low usefulness in biological monitoring. ACGIH, besides, should also introduce "B" (background) notation, at present not considered for the BEI indicated for urinary TTCA.

[Active search of work related tumours: preliminary findings]

The OCCAM (Occupational Cancer Monitoring) project enabled the active detection of occupational cancer cases in Lombardy Region.

METHODS

OCCAM is based on a record linkage with social security files to obtain occupational histories for all subjects having worked in private firms, since 1974. It provides risks by area, site and job.

RESULTS

271 incident cancer cases obtained by hospital discharge record in the period 2001-2002 where investigate to assess eventually their occupational origin. Approximately 38% where considered to be occupational cancers.

CONCLUSIONS

OCCAM provides name of the firms and their economic activity completed by information coming from OCCAM risks ascertainment and deeper knowledge on productive cycle retained by local occupational health services. Thus this system can lead to detection of many cancer cases of occupational origin suitable for compensation and determine strategies for the improvement of the work environment.

[Reactive anxiety crisis: a unique case of work injury]

The present study aims to describe a unique case in view of the disease diagnosed, the conditions of onset and the management by INAIL (Italian National Institute of Insurance for Injuries at Work and Occupational Diseases). A worker, after a verbal, animated dispute with some collegues, had an acute psychiatric agitation attack and went to the nearest emergency room, where he was investigated. No neuropsychiatric alteration was diagnosed, but based on anamnestic data, the physicians diagnosed an anxiety crisis reactive to work environment. A medical certificate for injury at work was produced and sent to the Insurance Board (INAIL). The worker was off work for 105 days diagnosed with a persistent anxious depressive syndrome, secondary to the traumatic event. INAIL reassessed the case later and confirmed only the first 30 days as due to work accident, while the following period was judged as related to affectivity disturbance due to common disease, not to work environment. Our case opens new perspective for the occupational physician in the assessment of ASD as work injury and of PTSD as professional disease, suggesting to give more attention to psychiatric health of workers.

[Asthenopia and work at video display terminals: study of 191 workers exposed to the risk by administration of a standardized questionnaire and ophthalmologic evaluation]

VDT (Visual Display Terminals) are commonly used in a wide range of occupational fields. Over the last ten years a number of studies have shown that ocular symptoms are the form of discomfort most frequently experienced by subjects who work at VDT. The symptoms as a whole characterize a complex syndrome named "asthenopia" and have been seen as a consequence of prolonged, fixed and closely oriented vision. In our study we have evaluated data derived from a standardized questionnaire (a series of questions elaborated and promoted by the Italian Society of Occupational Medicine and Industrial Hygiene). It was administered to a group of 191 workers who utilise VDT for more than 20 hours each week. We also took into consideration the results of ophthalmologic medical examinations performed on this particular group of workers. Prevalence of occupational asthenopia we found to be lower in this group than in the case of other reported investigations, though it proved to be higher in the case of female subjects. According to the Literature, symptoms intensity is related to the duration of weekly VDT use, there being no significant association with the number of years spent working at VDT. Our results show that prevalence of asthenopia was not significantly influenced by refractive alterations and this unexpected outcome might be explained by taking into account the small-size group of subjects affected by hypermetropic defects. It is well known that these are the most important factors in conditioning asthenopia. Our finding indicates the need for further research, which should include a larger group of VDT workers with refractive alterations and furthermore take into consideration environmental variables such as climate and illumination, since these are co-aetiological factors, known or suspected, of occupational asthenopia.

The Italian surveillance system for occupational cancers: characteristics, initial results, and future prospects

BACKGROUND

Occupational cancer monitoring is important for cancer prevention and public health protection. A surveillance system for identifying occupational cancer risks and cancer cases in Italy that are likely to be of occupational origin using information available in the Italian Social Security archives was created and assessed. Persons employed in the private sector, the employing company, its industrial sector, and years of employment are available in these archives.

METHODS

A method to find known occupational hazards was first tested using a case-control approach. Cases were from six Italian cancer registries (CRs) and controls were sampled from source populations and as "exposure" the economic sector of the employing company was used. The potential of using hospital discharge records as case sources was subsequently assessed: these cover larger populations and are available more quickly than CR case series.

RESULTS

In the CR-based study many known occupational cancer risks related to specific industrial sectors were identified. By using cases from hospital discharge records many industries at risk were identified, as well as cases of recent diagnosis likely to be of occupational origin. However, for some industrial sectors (e.g., the chemical industry) the approach was unable to detect any excess risk. Furthermore, information on employees in important areas like agriculture, self-employment, and the public sector is not available in the Social Security archives.

CONCLUSIONS

This approach appears to be a promising low-cost method for occupational cancer surveillance, at least for some industries, and can be easily implemented in other countries.

[Occupational risk and prevention in the biotechnology industry: a review]

BACKGROUND

The biotechnology industry has expanded greatly in the last 20-30 years and has led to a number of applications in different sectors of work, i.e., medical and pharmaceutical, agricultural, chemical, energetic and others. Nowadays hundreds of thousands of workers worldwide are employed in biotechnology plants. Health and safety issues related to such working activities are considered as relevant to workers as well as to the general public. In particular, when compared to traditional biotechnology, modern methods of processing microrganisms have given rise to public concern that they might generate hazards to human beings and to the environment.

OBJECTIVES AND METHODS

After summarizing the most important products and fields of application, the paper sets out to detail potential adverse effects for the health of biotechnology workers; in addition, an analysis of the literature highlights the various concepts of primary and secondary prevention.

RESULTS AND CONCLUSION

Along with occupational risk factors common to other working activities (i.e. the well-known physical and chemical hazards), the peculiarity of handling microrganisms and/or different biologic systems may induce infections, immunological alterations or non-infective and non-immunologic toxic reactions in the workers involved The need is emphasized for an accurate risk assessment, careful control by means of the current monitoring strategies and implementation of the confinement measures, taking into account the criteria set by Italian legislation for occupational biological risk. Lastly, attention is focussed on examinations for the medical surveillance of workers at risk.

Arrhythmogenesis in catecholaminergic polymorphic ventricular tachycardia: insights from a RyR2 R4496C knock-in mouse model

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited disease characterized by life threatening arrhythmias and mutations in the gene encoding the ryanodine receptor (RyR2). Disagreement exists on whether (1) RyR2 mutations induce abnormal calcium transients in the absence of adrenergic stimulation; (2) decreased affinity of mutant RyR2 for FKBP12.6 causes CPVT; (3) K201 prevent arrhythmias by normalizing the FKBP12.6-RyR2 binding. We studied ventricular myocytes isolated from wild-type (WT) and knock-in mice harboring the R4496C mutation (RyR2(R4496C+/-)). Pacing protocols did not elicit delayed afterdepolarizations (DADs) (n=20) in WT but induced DADs in 21 of 33 (63%) RyR2(R4496C+/-) myocytes (P=0.001). Superfusion with isoproterenol (30 nmol/L) induced small DADs (45%) and no triggered activity in WT myocytes, whereas it elicited DADs in 87% and triggered activity in 60% of RyR2(R4496C+/-) myocytes (P=0.001). DADs and triggered activity were abolished by ryanodine (10 micromol/L) but not by K201 (1 micromol/L or 10 micromol/L). In vivo administration of K201 failed to prevent induction of polymorphic ventricular tachycardia (VT) in RyR2(R4496C+/-) mice. Measurement of the FKBP12.6/RyR2 ratio in the heavy sarcoplasmic reticulum membrane showed normal RyR2-FKBP12.6 interaction both in WT and RyR2(R4496C+/-) either before and after treatment with caffeine and epinephrine. We suggest that (1) triggered activity is the likely arrhythmogenic mechanism of CPVT; (2) K201 fails to prevent DADs in RyR2(R4496C+/-) myocytes and ventricular arrhythmias in RyR2(R4496C+/-) mice; and (3) RyR2-FKBP12.6 interaction in RyR2(R4496C+/-) is identical to that of WT both before and after epinephrine and caffeine, thus suggesting that it is unlikely that the R4496C mutation interferes with the RyR2/FKBP12.6 complex.

Mercapturic acids of styrene in man: Comparability of the results obtained by LC/MS/MS and by HPLC-fluorimeter, and stability of samples under different storage conditions

Two analytical methods (HPLC-fluorimeter [HPLC-FLD] and tandem mass spectrometry LC/MS/MS) are available to assay phenyl-hydroxyethylmercapturic acids (PHEMAs), the mercapturic acids of styrene in humans. In the past, each method was used to check different populations of subjects, but until now no attempt has been made to compare the two methods. This study was designed to verify whether the two methods actually give comparable results. The influence of different conditions of sample storage in altering the concentration of PHEMAs was also investigated. Urine samples were collected at the beginning and at the end of the workshift from 10 workers exposed to different levels of styrene. Each sample was analysed both by LC/MS/MS after storage under different conditions (respectively, at -20 and +4 degrees C, and after repeated freezing-thawing cycles), and by HPLC-FLD (in the same conditions of storage). Strong correlations were found between the two methods both for total PHEMAs and for each of the isomers measured, including the minor (S,R)-M1. Also an alternative approach, the Bland-Altman test, confirmed the agreement between the two methods. The different storage conditions tested did not decrease the concentration of PHEMAs but, surprisingly, a clear trend to increase was shown, particularly for (R,R)-M1, (S,R)-M2 and (R,R)-M2 in samples stored at +4 degrees C for 1 week. In conclusion, the study demonstrates that the methods give comparable results. Indirectly, this confirms also the main characteristics of PHEMAs, showed in the previous experiments: low biotransformation rates of styrene into PHEMAs; large inter-individual variability; and the presence of a clear preference in the excretion of the isomers deriving from (S)-styrene oxide. PHEMAs appear stable under different storage conditions, but further studies are needed to explain the increase of levels that occurs when samples are not kept frozen. To avoid pre-analytical errors, samples collected for biomonitoring or research purposes should be frozen as soon as possible, and thawed only one time just before the analysis.