Maria Luisa Scapellato

Short-Term Effects of Particulate Matter: An Inflammatory Mechanism?

“Would you tell me please, which way I ought to go from here,” asked Alice. “That depends a good deal on where you want to go to,” said the cat. (Lewis Carroll, Alices Adventures in Wonderland) A large number of epidemiological studies show positive correlations between increasing levels of particulate matter (PM) in urban air and short-term morbidity and mortality for diverse acute cardiopulmonary diseases. Brought about by PM increments, inflammation is thought to exacerbate preexisting inflammatory diseases. Experimental evidence suggests a hierarchical oxidative stress model, in which a weakened antioxidant defense, as observed in disease or induced by inhaled particles, increases the PM ability to cause lung inflammation, accounting for exacerbations that occur in asthmatics and in patients with chronic obstructive lung disease. The role of PM-induced inflammation leading to acute cardiovascular events such as arrhythmia, heart failure, and myocardial infarction is more speculative. There is neither clear-cut evidence in humans that inhaled PM could get as far as blood circulation nor that proinflammatory mediators are significantly released from inflamed lung tissues, nor that blood coagulability is critically altered. As a whole, data in humans indicate that short-term inflammatory responses to PM are not always detected; they are usually mild and loosely correlated with functional changes. Among these studies, the diversity of PM characteristics, dose metrics, and endpoints hampers a clear discerning of inflammatory mechanism(s). Thus, the question arises as to whether inflammation represents the mechanism of acute cardiopulmonary PM toxicities in susceptible individuals, or rather an event that may coexist with other relevant mechanism(s). This review article discusses the evidence in humans linking short-term PM increments to inflammation and to exacerbations of cardiopulmonary diseases. Although there is a large amount of data available, there still remains a gulf between the number of epidemiological and panel studies and that of controlled exposures. Research on controlled exposure needs expanding, so that the results of time-series and panel studies will be better understood and short-term standards for human exposure may be more confidently allocated.

Chlorpyrifos-induced delayed polyneuropathy

Chlorpyrifos [0,0-diethyl 0-(3,5,6-trichloro-pyridyl) phosphorothioate] caused delayed polyneuropathy in man. Contrary to previous studies, we report here that it also causes delayed polyneuropathy in the hen, the animal model for this toxicity. The minimal neuropathic dose was 60–90 mg/kg p.o., corresponding to 4–6 times the estimated LD50. Consequently, pralidoxime (2-PAM) in conjunction with atropine was necessary to reverse acetylcholinesterase (AChE) inhibition and cholinergic toxicity in hens given high enough doses of chlorpyrifos to cause neuropathy. Chlorpyrifos was slowly absorbed after single oral doses and the threshold of inhibition (>70%) of neuropathy target esterase (NTE), the putative target for delayed neuropathy, was reached within 5–6 days. High AChE inhibition (>90%), however, was measured within hours after dosing because of the higher potency of chlorpyrifos to inhibit this enzyme. In vitro studies showed that chlorpyrifos-oxon, the active metabolite of chlorpyrifos, was 10–20 times more active against AChE than against NTE, confirming the clinical observation. No differences were seen between human and hen enzymes in this respect. Hen and human brain homogenates contain A-esterases which hydrolysed chlorpyrifos to about the same extent in both species. In conclusion, chlorpyrifos causes delayed polyneuropathy in the hen, as was reported in man. The reasons for previous negative data in the hen are probably due to the relatively lower doses which were used. Judging from in vitro studies with hen and human enzymes, there are no differences in the two species as far as their relative sensitivity to delayed polyneuropathy. It is likely that delayed polyneuropathy would develop in both species only after severe cholinergic toxicity requiring aggressive antidotal treatment.

Phenylmethanesulfonyl fluoride elicits and intensifies the clinical expression of neuropathic insults

It has been recently reported that phenyl-methanesulfonyl fluoride (PMSF) when given to hens after a neuropathic organophosphate (OP) promotes organophosphate-induced delayed polyneuropathy (OPIDP). Chicks are resistant to OPIDP despite high inhibition/aging of neuropathy target esterase (NTE), the putative target of OPIDP initiation. However, when PMSF (300 mg/kg s.c.) is given to chicks after di-butyl 2,2-dichlorovinyl phosphate (DBDCVP, 1 or 5 mg/kg s.c.), OPIDP is promoted. Inhibition/aging of at least 30% of NTE was thought to be an essential prerequisite for promotion to be elicited in adult hens. However, we observed in hens that when NTE is maximally affected (>90%) by phenyl N-methyl N-benzyl carbamate (40 mg/kg i.V.), a non-ageable inhibitor of NTE, and then PMSF is given (120 mg/kg/day s.c. × 3 days) clinical signs of neuropathy become evident. Methamidophos (50 mg/kg p. o. to hens), which produces in vivo a reactivatable form of inhibited NTE, was shown either to protect from or promote OPIDP caused by DBDCVP (0.45 mg/kg s. c), depending on the sequence of dosing. Because very high doses of methamidophos cause OPIDP, we considered this effect to be a “self-promoted” OPIDP. We concluded that NTE inhibitors might have different intrinsic activities for producing OPIDP once NTE is affected. Aging might differentiate highly neuropathic OPs, like DBDCVP, from less neuropathic OPs, like methamidophos, or from the least neuropathic carbamates, which require promotion in order for neuropathy to be expressed. Retrograde axonal transport in motor fibers was measured as the accumulation of125 I-tetanus toxin in spinal cord after injection in the gastrocnemius muscle of chicks treated either with DBDCVP (5 mg/kg s.c.) or with DBDCVP followed by PMSF (300 mg/kg s.c). Retrograde axonal transport was reduced in both groups (to about 50%, 10 days after dosing) and returned to normal 27 days after dosing. However, DBDCVP-treated chicks had a mild neuropathy which recovered relatively quickly, whereas chicks to which PMSF was also given had more severe signs which did not recover by day 27. We concluded that promotion affects a site other than NTE and that it acts at a point downstream from initiation. PMSF was also shown to promote 2,5-hexanedione (2,5-HD) neuropathy. 2,5-HD was given to hens at doses (200 mg/kg/day i.p. × 8 days) which caused mild and reversible neuropathy. When PMSF (120 mg/kg/day × 2 days at the end of 2,5-HD treatment) was given, more severe and irreversible signs of neuropathy were observed. We conclude that promotion might be a common feature in neuropathies of different origin.

Correlation between environmental and biological monitoring of exposure to benzene in petrochemical industry operators

The present work was aimed to study in petrochemical industry operators the correlation, if any, between environmental exposure to low levels of benzene and two biological exposure indexes in end-shift urine, i.e. trans, trans-muconic acid (t,t-MA) and S-phenylmercapturic acid (SPMA). Exposure to benzene was assessed in 133 male subjects employed in outdoor operations in a petrochemical plant, using personal passive-diffusive air samplers worn at the breathing zone; adsorbed benzene was determined by GC-FID analysis. S-PMA was determined by a new HPLCMS/MS method, after (quantitative) acidic hydrolysis of the cysteine conjugate precursor. t,t-MA was measured by an HPLC-UV method. Smoking habits were assessed by means of a self-administered questionnaire. Both environmental and biological monitoring data showed that benzene exposure of petrochemical industry operators was low (mean values were 0.014ppm, 101mug/g creat, and 2.8mug/g creat, for benzene, t,t-MA, and S-PMA, respectively) if compared with the ACGIH limits. Cigarette smoking was confirmed to be a strong confounding factor for the urinary excretion of both metabolites: statistically significant increases of t,t-MA and S-PMA levels were recorded in smokers when compared to non-smokers (p<0.0001). The best correlation found was that between exposure to benzene and S-PMA levels, particularly in non-smokers. This was partly due to the hydrolysis of the S-PMA precursor N-acetyl-S-(1,2-dihydro-2-hydroxyphenyl)-l-cysteine, a crucial step of the new analytical method used, which indeed reduced the variability of the results by means of an improved standardization of this critical preanalytical factor. A weaker correlation was found between exposure to benzene and t,t-MA, possibly explained by the fact that the latter is also a metabolite of sorbic acid, a common diet component. In summary, even at such low levels of exposure, urinary metabolites proved to be a useful tool for assessing individual occupational exposure to benzene, S-PMA appearing to be a more specific biomarker than t,t-MA, particularly in non-smokers.

Individual exposure to particulate matter and the short-term arrhythmic and autonomic profiles in patients with myocardial infarction

AIMS Epidemiological studies show that peak exposure to air pollution is associated with increased morbidity and mortality from cardiovascular events. Panel and controlled exposure studies show that particulate matter (PM) may influence the parasympathetic regulation of the heart. The aim of this study was to concurrently measure individual exposure to PM of various sizes, heart rate variability (HRV), and electrical instability in patients with myocardial infarction. METHODS AND RESULTS Personal exposures to PM(10), PM(2.5), and PM(0.25) was measured over 24 h in 39 patients (36 males, 3 females; mean age 60.3 years) with prior myocardial infarction (>6 months). Simultaneously, a 24 h ECG was recorded and then analysed for HRV and ventricular arrhythmias. Breath condensate and blood samples also were collected at the end of monitoring to measure several indexes of inflammation. Negative correlation was found between HRV and exposure to PM(0.25) in a group of patients not taking beta-blockers. More severe ventricular arrhythmias were observed at the highest concentrations of PM(10) and PM(2.5). Indexes of inflammation in either breath condensate or blood did not correlate with PM exposures. CONCLUSION Our study shows that exposure to ultrafine particles is associated with autonomic dysregulation in selected patients with myocardial infarction. More severe arrhythmias occur at the highest exposures to larger particles. Nevertheless, the underlying mechanisms remain hypothetical because inflammation may be evoked by PM or be related to the disease itself.

Personal PM10 exposure in asthmatic adults in Padova, Italy: seasonal variability and factors affecting individual concentrations of particulate matter.

Personal exposure to PM(10) measured in different seasons in a sample of asthmatic subjects living in Padova (Northern Italy) was compared with simultaneously measured outdoor PM(10) concentrations. The specific contribution of ambient PM(10) and other factors to individual exposure was evaluated in one of the areas of Europe with the worst air pollution. Thirty-one asthmatic subjects (21 non-smokers and 10 smokers) carried personal PM(10) monitors for six 24-hr sessions, in different seasons of the year. Concomitant daily 24-hr ambient PM(10) concentrations were measured by air quality monitoring networks. A multivariate analysis was performed to identify factors explaining personal exposure to PM(10), using a random effect model. The analysis on the 31 subjects referred to a total of 155 observations. The mean personal PM(10) exposure was higher (range 79.3-126.1microg/m(3)) than the outdoor concentrations (range 37.3-85.4microg/m(3)) in all seasons; and personal exposures varied less than outdoor PM(10) levels from one season to another. Smokers had significantly higher personal PM(10) concentrations than non-smokers (127.99 vs 78.8microg/m(3); T=-5.70; p<0.001). Moderate correlations emerged between outdoor and personal PM(10) concentrations. The correlation improved after excluding subjects exposed to active or passive smoking (median Pearsons R 0.41 vs 0.26). Considering all the subjects, smoking was the main factor affecting personal exposure, contributing to 41% of the variability. Outdoor PM(10) concentrations (25%), temperature (12%) and season (15%) also contributed to personal PM(10) exposure. Outdoor PM(10) (46%), temperature (20%), season (19%) and time spent indoors (6%) were significantly associated with personal exposure in non-smokers. We concluded that it is crucial to perform personal monitoring and to evaluate the complexity of factors that contribute to individual PM exposure. While tobacco smoke was the primary source of PM(10) in all subjects, the contribution of ambient components was particularly relevant for the personal exposure levels of our non-smokers living in a highly-polluted environment.

Influence of glutathione S-transferases polymorphisms on biological monitoring of exposure to low doses of benzene

The environmental and biological monitoring of benzene exposure is crucial to prevent the toxic effects of this solvent in workers. The degree of correlation, however, between the two and of different biomarkers among them varies, particularly at low levels of exposure, depending on various factors, including variability in metabolizing enzymes and smoking habits. To investigate these further, a cohort of 28 petrochemical workers (6 smokers and 22 non smokers) was monitored throughout ten consecutive days, on two occasions, two years apart, by collecting in total 173 environmental and biological samples. The airborne benzene levels, the urinary t,t-muconic acid (t,t-MA) and S-phenylmercapturic acid (S-PMA) concentrations, and the glutathione S-transferases (GST) M1 and T1 genotypes were measured. S-PMA was the only metabolite statistically correlated with airborne benzene levels (r=0.447, P<0.0001), particularly in non smokers (r=0.667, P<0.0001), the smoking habit being the only variable influencing metabolite excretion. Finally, a reduced S-PMA excretion was found to be associated with the GSTT1, but not the GSTM1, null genotype. In conclusion, the results show that S-PMA, but not t,t-MA, is able to monitor exposure to low benzene concentrations and confirm that the GSTT1 null genotype has a significant influence on metabolite excretion. The influence of the GSTT1 null genotype, however, was low, even when studying each subject with several urine samples.

Validation of a radial diffusive sampler for measuring occupational exposure to 1,3-butadiene

1,3-Butadiene (BD) is a major industrial chemical used in the manufacture of rubbers and latexes; it is also a ubiquitous environmental pollutant whose major source is traffic. Occupational exposure to (BD) can occur both during its production and during its use as a raw material. The objective of the study was the laboratory and field validation of a new diffusive sampler for BD. The nominal sampling rate of the Radiello diffusive sampler filled with Carbopack X is 30.5 cm(3)/min, at 0.177 mg/m(3), 20 °C and 50% relative humidity (RH), for an 8-h exposure time. A model can be used for calculating the sampling rate as a function of temperature, time and RH. The concentration does not affect the sampling rate above 30 μg/m(3). The measurement uncertainty (k=2), calculated both by laboratory data and by field comparison according to International Standard Organization (ISO) 13752, satisfies the EN 482:2006 requirement for measurements between 0.1 and 0.5 times the threshold limit value-time weighted average (TLV-TWA) (uncertainty<50%). For field validation study, 38 workers exposed to BD and 20 administrative employees, as the control group, underwent environmental and biological monitoring. Personal exposure to BD was measured by diffusive samplers (Radiello) in comparison with active samplers. The BD exposure levels detected for the exposed subjects were low (mean 0.059, range <0.010-1.340 mg/m(3)) but higher than the controls levels, all below 0.010 mg/m(3). The comparison between diffusive and active (pumped) air sampling showed a good correlation, with no systematic deviation from the ideal values of the intercept and slope of the optimized regression line. The concentrations of two biomarkers were also determined on urine samples, collected at the end of the work-shift: unchanged BD, by GC-MS, and the metabolite dihydroxybutylmercapturic acid (DHBMA), by HPLC-MS/MS. The urinary excretion of the biomarkers was on average higher in the exposed group (urinary BD: mean 8.8, range <1-48.1 ng/l; DHBMA: mean 0.232, range 0.016-0.572 mg/l) than in controls (urinary BD: mean 6.4, range 2.6-14.5 ng/l; DHBMA: mean 0.205, range 0.037-0.602 mg/l), but a statistically significant difference was achieved only for unchanged BD and not for DHBMA. In conclusion, the environmental monitoring measured by diffusive samplers (Radiello) appears to be a reliable method for the assessment of exposure to low levels of airborne BD and a convenient alternative to the conventional active sampling.

2-Methylanthraquinone as a Marker of Occupational Exposure to Teak Wood Dust in Boatyards

A new gas chromatographic/mass spectrometric (GC/MS) method was developed to detect 2-methylanthraquinone (2-MeA) in wood dust. 2-MeA is present in teak wood (a suspected human carcinogen) but not in oak, beech, mahogany, birch, ash or pine. The method involved collection of workplace dust on filters and extraction of 2-MeA with methanol and GC/MS analysis. The method was tested on teak wood dust samples (n = 43) collected on polyvinylchloride membrane filters during various work operations in four small factories making furniture and fittings for leisure craft and boatyards (air teak wood dust concentration: range 0.32-14.32 mg m(-3)). A high correlation coefficient for the content of 2-MeA versus teak dust was obtained (logarithmic correlation: y = 1.5308x + 0.0998, r = 0.9215). Determination of airborne 2-MeA is a useful technique to confirm occupational exposure to teak wood dust.

The Importance of Sampling Time and Coexposure to Acetone in the Biological Monitoring of Styrene-Exposed Workers

Abstract Forty-four workers exposed to styrene and acetone in the fiberglass industry were monitored on Monday and Thursday for 8 hours using passive dosimeters. The charcoal discs of the passive dosimeters were analyzed by gas chromatography. The 8-hour time-weighted average (TWA) exposure values ranged from 10 to 522 and 14 to 1581 mg/m3 on Monday and from 9 to 423 and 10 to 579 on Thursday for styrene and acetone, respectively. Urine samples were collected at the end of the work shift and before the start of the work shift the next morning (Tuesday and Friday). Mandelic acid and phenylglyoxylic acid were measured in the urine using a high pressure liquid chromatography method; values were expressed in milligrams/gram creatinine. Styrene TWA exposure values significantly correlated with the sum of metabolites at the end of the workday (r = 0.60 on Monday and r = 0.77 on Thursday) and also the next morning (r = 0.87 on Tuesday and r = 0.84 on Friday). Mandelic acid was always correlated with exposure bet...