III Italian Consensus Conference on Malignant Mesothelioma of the Pleura. Epidemiology, Public Health and Occupational Medicine related issues.

The III Italian Consensus Conference on Pleural Mesothelioma (MM) convened on January 29th 2015. This report presents the conclusions of the 'Epidemiology, Public Health and Occupational Medicine' section. MM incidence in 2011 in Italy was 3.64 per 100,000 person/years in men and 1.32 in women. Incidence trends are starting to level off. Ten percent of cases are due to non-occupational exposure. Incidence among women is very high in Italy, because of both non-occupational and occupational exposure. The removal of asbestos in place is proceeding slowly, with remaining exposure. Recent literature confirms the causal role of chrysotile. Fibrous fluoro-edenite was classified as carcinogenic by IARC (Group 1) on the basis of MM data. A specific type (MWCNT-7) of Carbon Nanotubes was classified 2B. For pleural MM, after about 45 years since first exposure, the incidence trend slowed down; with more studies needed. Cumulative exposure is a proxy of the relevant exposure, but does not allow to distinguish if duration or intensity may possibly play a prominent role, neither to evaluate the temporal sequence of exposures. Studies showed that duration and intensity are independent determinants of MM. Blood related MM are less than 2.5%. The role of BAP1 germline mutations is limited to the BAP1 cancer syndrome, but negligible for sporadic cases. Correct MM diagnosis is baseline; guidelines agree on the importance of the tumor gross appearance and of the hematoxylin-eosin-based histology. Immunohistochemical markers contribute to diagnostic confirmation: the selection depends on morphology, location, and differential diagnosis. The WG suggested that 1) General Cancer Registries and ReNaM Regional Operational Centres (COR) interact and systematically compare MM cases; 2) ReNaM should report results presenting the diagnostic certainty codes and the diagnostic basis, separately; 3) General Cancer Registries and COR should interact with pathologists to assure the up-to-date methodology; 4) Necroscopy should be practiced for validation. Expert referral centres could contribute to the definition of uncertain cases. Health surveillance should aim to all asbestos effects. No diagnostic test is recommended for MM screening. Health surveillance should provide information on risks, medical perspective, and smoking cessation. The economic burden associated to MM was estimated in 250,000 Euro per case.

Physicochemical and toxicological profiling of ash from the 2010 and 2011 eruptions of Eyjafjallajökull and Grímsvötn volcanoes, Iceland using a rapid respiratory hazard assessment protocol.

The six week eruption of Eyjafjallajökull volcano in 2010 produced heavy ash fall in a sparsely populated area of southern and south eastern Iceland and disrupted European commercial flights for at least 6 days. We adopted a protocol for the rapid analysis of volcanic ash particles, for the purpose of informing respiratory health risk assessments. Ash collected from deposits underwent a multi-laboratory physicochemical and toxicological investigation of their mineralogical parameters associated with bio-reactivity, and selected in vitro toxicology assays related to pulmonary inflammatory responses. Ash from the eruption of Grímsvötn, Iceland, in 2011 was also studied. The results were benchmarked against ash from Soufrière Hills volcano, Montserrat, which has been extensively studied since the onset of eruptive activity in 1995. For Eyjafjallajökull, the grain size distributions were variable: 2-13 vol% of the bulk samples were <4 µm, with the most explosive phases of the eruption generating abundant respirable particulate matter. In contrast, the Grímsvötn ash was almost uniformly coarse (<3.5 vol%<4 µm material). Surface area ranged from 0.3 to 7.7 m2 g(-1) for Eyjafjallajökull but was very low for Grímsvötn (<0.6 m2 g(-1)). There were few fibre-like particles (which were unrelated to asbestos) and the crystalline silica content was negligible in both eruptions, whereas Soufrière Hills ash was cristobalite-rich with a known potential to cause silicosis. All samples displayed a low ability to deplete lung antioxidant defences, showed little haemolysis and low acute cytotoxicity in human alveolar type-1 like epithelial cells (TT1). However, cell-free tests showed substantial hydroxyl radical generation in the presence of hydrogen peroxide for Grímsvötn samples, as expected for basaltic, Fe-rich ash. Cellular mediators MCP-1, IL-6, and IL-8 showed chronic pro-inflammatory responses in Eyjafjallajökull, Grímsvötn and Soufrière Hills samples, despite substantial differences in the sample mineralogy and eruptive styles. The value of the pro-inflammatory profiles in differentiating the potential respiratory health hazard of volcanic ashes remains uncertain in a protocol designed to inform public health risk assessment, and further research on their role in volcanic crises is warranted.

The role of iron impurities in the toxic effects exerted by short multiwalled carbon nanotubes (MWCNT) in murine alveolar macrophages.

Lung toxicity mediated by multiwalled carbon nanotubes (MWCNT) has been widely demonstrated and recently associated with induction of carcinogenic asbestos-like effects, but the chemical features that drive this toxic effect have still not been well elucidated. The presence of metals as trace contaminants during MWCNT preparation, in particular iron (Fe) impurities, plays an important role in determining a different cellular response to MWCNT. Our goal was to clarify the mechanisms underlying MWCNT-induced toxicity with correlation to the presence of Fe impurities by exposing murine alveolar macrophages to two different MWCNT samples, which differed only in the presence or absence of Fe. Data showed that only Fe-rich MWCNT were significantly cytotoxic and genotoxic and induced a potent cellular oxidative stress, while Fe-free MWCNT did not exert any of these adverse effects. These results confirm that Fe content represents an important key constituent in promoting MWCNT-induced toxicity, and this needs to be taken into consideration when planning new, safer preparation routes.

Lichens on asbestos-cement roofs: bioweathering and biocovering effects.

Asbestos-cement roofs, the most widespread sources of airborne, toxic and carcinogenic asbestos fibres, are often colonized by lichens. Since these latter are physical and chemical weathering agents, they have been often considered as significant responsible of disaggregation processes increasing fibre dispersion. Consequently, official guidelines for the management of asbestos often suggest their removal. Weathering and/or covering effects of lichens on asbestos-cement, however, have never been deeply investigated and available procedures to evaluate asbestos-cement aging do not take the biological colonization into account. In this study we show that a 25% lichen cover modifies physical and chemical properties of asbestos-cement sheets containing chrysotile and crocidolite fibres. By innovatively coupling pull up tests and image analysis of linear structures, we show that fibre loss is significantly lower ( approximately 30%) where lichens develop and offer a physical barrier to the fibre detachment. Below the most covering lichens (Acarospora cervina, Candelariella ssp.), chrysotile and crocidolite undergo a partial incongruent dissolution, which in laboratory assays generally determined a reduction of their surface reactivity. Because of their biocovering and bioweathering effects, lichens on asbestos-cement play a role which differs from the current public opinion and the assumptions of some official regulations, acting as effective spontaneous bioattenuation agents.

Iron inhibits the nitric oxide synthesis elicited by asbestos in murine macrophages.

Crocidolite fibers stimulated nitric oxide synthase (NOS) activity and expression in glial and alveolar murine macrophages: this effect was inhibited by iron supplementation and enhanced by iron chelation. We suggest that in these cells crocidolite stimulates NOS expression by decreasing the iron bioavailability and activating an iron-sensitive transcription factor.

Surface reactivity in the pathogenic response to particulates.

The peculiar characteristics of dust toxicity are discussed in relation to the processes taking place at the particle-biological medium interface. Because of surface reactivity, toxicity of solids is not merely predictable from chemical composition and molecular structure, as with water soluble compounds. With particles having the same bulk composition, micromorphology (the thermal and mechanical history of dust and adsorption from the environment) determines the kind and abundance of active surface sites, thus modulating reactivity toward cells and tissues. The quantitative evaluation of doses is discussed in comparisons of dose-response relationships obtained with different materials. Responses related to the surface of the particle are better compared on a per-unit surface than per-unit weight basis. The role of micromorphology, hydrophilicity, and reactive surface cations in determining the pathogenicity of inhaled particles is described with reference to silica and asbestos toxicity. Heating crystalline silica decreases hydrophilicity, with consequent modifications in membranolytic potential, retention, and transport. Transition metal ions exposed at the surface generate free radicals in aqueous suspensions. Continuous redox cycling of iron, with consequent activation-reactivation of the surface sites releasing free radicals, could account for the long-term pathogenicity caused by the inhalation of iron-containing fibers. In various pathogenicities caused by mixed dusts, the contact between components modifies toxicity. Hard metal lung disease is caused by exposure to mixtures of metals and carbides, typically cobalt (Co) and tungsten carbide (WC), but not to single components. Toxicity stems from reactive oxygen species generation in a mechanism involving both Co metal and WC in mutual contact. A relationship between the extent of water adsorption and biopersistence is proposed for vitreous fibers. Modifications of the surface taking place in vivo are described for ferruginous bodies and for the progressive comminution of chrysotile asbestos fibers.

Chemical characterization and reactivity of iron chelator-treated amphibole asbestos.

Iron in amphibole asbestos is implicated in the pathogenicity of inhaled fibers. Evidence includes the observation that iron chelators can suppress fiber-induced tissue damage. This is believed to occur via the diminished production of fiber-associated reactive oxygen species. The purpose of this study was to explore possible mechanisms for the reduction of fiber toxicity by iron chelator treatments. We studied changes in the amount and the oxidation states of bulk and surface iron in crocidolite and amosite asbestos that were treated with iron-chelating desferrioxamine, ferrozine, sodium ascorbate, and phosphate buffer solutions. The results have been compared with the ability of the fibers to produce free radicals and decompose hydrogen peroxide in a cell-free system in vitro. We found that chelators can affect the amount of iron at the surface of the asbestos fibers and its valence, and that they can modify the chemical reactivity of these surfaces. However, we found no obvious or direct correlations between fiber reactivity and the amount of iron removed, the amount of iron at the fiber surface, or the oxidation state of surface iron. Our results suggest that surface Fe3+ ions may play a role in fiber-related carboxylate radical formation, and that desferrioxamine and phosphate groups detected at treated fiber surfaces may play a role in diminishing and enhancing, respectively, fiber redox activity. It is proposed that iron mobility in the silicate structure may play a larger role in the chemical reactivity of asbestos than previously assumed.

Study of the stability of a paramagnetic label linked to mesoporous silica surface in contact with rat mesothelial cells in culture.

Stable radicals detectable by electron paramagnetic resonance (EPR) may be use in the investigation of early events in cell-particle toxicity. Piperidine-N-oxyl derivatives (nitroxides), covalently linked to the surface of a high surface area silica (used as model solid for the technique), served as probes in the investigation of the effects of incubation of silica particles with mesothelial cells. A mesoporous silica (MCM-41), prepared by precipitation from a micellar solution, was the most appropriate silica-based particle for this purpose, as its channels allow direct contact with small molecules but not with macromolecules. The cytotoxicity of this amorphous silica is very low, allowing relatively high particle loading in the cell cultures. Both the high surface area of the sample and the large amount of inorganic material extracted from the cell culture provide enough material to run reasonably intense EPR spectra. Computer-aided analysis of the EPR spectra of silica-bound nitroxides provided information on the sensitivity of the labeled silica monitoring different environments, e.g., to follow the path of particles in a mammalian cell culture. Upon contact of the particles with mesothelial cells, the mean distance among the labels at the silica surface decreased as a consequence of the release of oxidizing and/or radical moieties from the cells.

Alterations in protein glycosylation in PMA-differentiated U-937 cells exposed to mineral particles.

Carbohydrate moieties of cell glycoconjugates play a pivotal role in molecular recognition phenomena involved in the regulation of most biological systems and the changes observed in cell surface carbohydrates during cell activation or differentiation frequently modulate certain cell functions. Consequently, some aspects of macrophage response to particle exposure might conceivably result from alterations in glycosylation. Therefore, the effect of mineral particles on protein glycosylation was investigated in phorbol myristate acetate (PMA)-differentiated U-937. Jacalin, a lectin specific for O-glycosylated structures, showed a global increase in O-glycosylation in particle-treated cells. In contrast, no significant modifications were observed with concanavalin A, a lectin that recognizes certain N-glycosylated structures. The sialic acid-specific lectins Sambucus nigra agglutinin and Maackia amurensis agglutinin and the galactose-specific lectin Ricinus communis agglutinin revealed a complex pattern of alterations in glycoprotein glycosylation after crystalline silica or manganese dioxide treatments. Expression of sialyl Lewis(x), a glycosylated structure implicated in leukocyte trafficking, could not be detected in control or treated cells. This finding was consistent with the decrease in sialyl Lewis(x) expression observed during PMA-induced differentiation. In conclusion, various treatments used in this study induced quantitative as well as qualitative changes in protein glycosylation. Whether these changes are due to glycosidase release or to an alteration in glycosyltransferase expression remains to be determined. The potential functional implications of these changes are currently under investigation.

Spontaneous polymerisation on amphibole asbestos: relevance to asbestos removal.

Taking advantage of the spontaneous polymerisation of eugenol to lignin-like species catalysed by the surface of crocidolite fibres, a procedure is proposed, possibly useful in asbestos removal and disposal, where the polymer avoids the release of airborne fibres and also scavenges ROS (reactive oxygen species).

Free radical generation at the solid/liquid interface in iron containing minerals.

The potential for free radical release has been measured by means of the spin trapping technique on three kinds of iron containing particulate: two asbestos fibers (chrysotile and crocidolite); an iron-exchanged zeolite and two iron oxides (magnetite and haematite). DMPO (5,5'-dimethyl-1-pirroline-N-oxide), used as spin trap in aqueous suspensions of the solids, reveals the presence of the hydroxyl and carboxylate radicals giving rise respectively to the two adducts [DMPO-OH] and [DMPO-CO2], each characterized by a well-defined EPR spectrum. Two target molecules have been considered: the formate ion to evidence potential for hydrogen abstraction in any biological compartment and hydrogen peroxide, always present in the phagosome during phagocytosis. The kinetics of decomposition of hydrogen peroxide has also been measured on all solids. Ferrozine and desferrioxamine, specific chelators of Fe(II) and Fe(III) respectively, have been used to remove selectively iron ions. Iron is implicated in free radical release but the amount of iron at the surface is unrelated to the amount of radicals formed. Only few surface ions in a particular redox and coordination state are active. Three different kinds of sites have been evidenced: one acting as H abstracter, the other as a heterogeneous catalyst for hydroxyl radical release, the third one related to catalysis of hydrogen peroxide disproportionation. In both mechanisms of free radical release, the Fe-exchanged zeolite mimics the behaviour of asbestos whereas the two oxides are mostly inert. Conversely magnetite turns out to be an excellent catalyst for hydrogen peroxide disproportionation while haematite is inactive also in this reaction. The results agree with the implication of a radicalic mechanism in the in vitro DNA damage and in the in vivo toxicity of asbestos.

Free radical generation in the toxicity of inhaled mineral particles: the role of iron speciation at the surface of asbestos and silica.

Free radical generation at the particle/biological fluid interface is one of the chemical processes that contributes to pathogenicity. In order to investigate the role played by iron, fibres of crocidolite asbestos have been modified by thermal treatments to alter their surface iron content. Two radical mechanisms, HO* from H2O2 and cleavage of a C-H bond, which are both active on the original fibres, have been tested on the modified fibres. C-H cleavage is dependent on Fe(II) abundance and location and is suppressed by surface oxidation while HO* release appears independent of the oxidation state of iron. Quartz specimens with different levels of iron impurities have been tested in a similar manner. A commercially available quartz (Min-U-Sil 5) containing trace levels of iron is also active in both tests, but reactivity is not fully suppressed by treatment with desferrioxamine, which should remove/inactivate iron. The radical yield attained is close to the level produced by a pure quartz dust, suggesting the presence of active sites other than iron. Ascorbic acid reacts with both crocidolite and quartz, with subsequent depletion of the level of antioxidant defences when particle deposition occurs in the lung lining layer. Following treatment with ascorbic acid the radical yield increases with quartz, but decreases with asbestos. Selective removal of iron and silicon from the surface may account for the differences in behaviour of the two particulates.

Free radical activity of natural and heat treated amphibole asbestos.

The amphibole minerals amosite and crocidolite were subjected to calcination and to hydrothermal treatment in order to study the effect of these heat treatments on the ability of the minerals to trigger formation of free radicals, which is known to be a main factor causing asbestosis and other asbestos-induced diseases. Free radical activity of the natural and heat treated minerals was studied by using supercoiled DNA (pUC18 plasmid) as a target molecule, and also by means of EPR spectroscopy. It was shown that after calcination of the natural minerals at 1073 K their free radical activity was strongly decreased These results, which may have relevant consequences for asbestos technology, were correlated with concomitant alteration of the structure and surface chemistry of the minerals during calcination.

Role of iron in the reactivity of mineral fibers.

Any foreign body containing iron may be (or become) highly toxic in vivo. If its solubility in water is poor, surface chemistry governs the reactivity at the solid-liquid interface. Iron toxicity thus increases with the extent of exposed surface. Iron of endogenous origin may also be deposited on the particle surface and be activated under particular circumstances. The chemical processes that implicate surface iron as a primary cause of toxicity are: free radical release, mobilization by chelators, iron-catalyzed reactions. Three kinds of solids are compared: (i) well-known toxic materials, for example asbestos; (ii) non-toxic iron oxides; and (iii) model solids with surface exposed iron prepared for investigations on the reactivity of iron in biological media. The iron content of the solid is not directly related to the biological response: only a small fraction of ions, in a well-defined coordination and redox state, appears involved in the toxicity of the mineral dust.

Silica and renal diseases: no longer a problem in the 21st century?

Silicosis and other occupational diseases are still important even in the most developed countries. In fact, at present, silica exposure may be a risk factor for human health not only for workers but also for consumers. Furthermore, this exposure is associated with many other different disorders besides pulmonary silicosis, such as progressive systemic sclerosis, systemic lupus erythematosus, rheumatoid arthritis, dermatomyositis, glomerulonephritis and vasculitis. The relationships between these silica-related diseases need to be clarified, but pathogenic responses to silica are likely to be mediated by interaction of silica particles with the immune system, mainly by activation of macrophages. As regards renal pathology, there is no single specific clinical or laboratory finding of silica-induced nephropathy: renal involvement may occur as a toxic effect or in a context of autoimmune disease, and silica damage may act as an additive factor on an existing, well-established renal disease. An occupational history must be obtained for all renal patients, checking particularly for exposure to silica, heavy metals, and solvents.

Variability of biological responses to silicas: effect of origin, crystallinity, and state of surface on generation of reactive oxygen species and morphological transformation of mammalian cells.

Variously modified quartz dusts and one amorphous diatomaceous earth have been compared in their potential to release HO* radicals and in their activity in the Syrian hamster embryo (SHE) cell transformation assay. Both original dusts, made up by well-crystallized quartz particles, or by mostly amorphous, variously shaped, silica particles, were active in HO* release, were cytotoxic, and induced morphological transformation in SHE cells. The cristobalite dust, obtained by heating quartz above the phase transition temperature, lost any activity in free radical release, cytotoxicity, and transforming potency. Surface-modified quartz dusts were obtained by a mild etching with HF, by depriving the surface of trace iron with deferoxamine, or by enriching it with iron. The chemical and biological activity decreased in all cases. Both iron-deprived and iron-enriched quartz were nearly inactive. A linear correlation was found between the amount of HO* released by the particles and the transformation frequency. When the SHE cell assay was performed in the presence of mannitol or antioxidant enzymes (superoxide dismutase [SOD] or catalase), the number of transformed cells markedly decreased. This effect was more pronounced for catalase and mannitol than for SOD. HO* release was reduced, but not suppressed, by deferoxamine. All the above results are consistent with the presence of two kinds of surface sites active in HO* release and cell transformation: (1) silicon-based radicals, abundant on freshly ground dusts, which generate the HO* radicals without the superoxide ion as intermediate; and (2) isolated iron centers where the Haber-Weiss cycle takes place, with the superoxide ion as intermediate. The activities of both sites are inhibited by mannitol or catalase, whereas only the last one is inhibited by SOD.

Cytotoxic and transforming effects of silica particles with different surface properties in Syrian hamster embryo (SHE) cells.

Several crystalline and amorphous silica dusts (two quartz of natural origin, one cristobalite of natural and two of biogenic origin, three amorphous diatomite earths and one pyrogenic amorphous silica) were studied in the SHE cell transformation assay, in order to compare their cytotoxic and transforming potencies and examine the role of the structure and of the state of the surface on these effects. Some samples were modified by grinding, etching and heating with the aim of establishing relationships between single surface properties and biological responses. The results showed that some quartz and cristobalite dusts (crystalline) as well as the diatomaceous earths (amorphous), but not the pyrogenic amorphous silica, were cytotoxic and induced morphological transformation of SHE cells in a concentration-dependent manner. The ranking in cytotoxicity was different from that in transforming potency, suggesting two separate molecular mechanisms for the two effects. The cytotoxic and transforming potencies were different from one dust to another, even among the same structural silicas. The type of crystalline structure (quartz vs cristobalite) and the crystalline vs biogenic amorphous form did not correlate with cytotoxic or transforming potency of silica dusts. Comparison of cellular effects induced by original and surface modified samples revealed that several surface functionalities modulate cytotoxic and transforming potencies. The cytotoxic effects appeared to be related to the distribution and abundance of silanol groups and to the presence of trace amounts of iron on the silica surface. Silica particles with fractured surfaces and/or iron-active sites, able to generate reactive oxygen species, induced SHE cell transformation. The results show that the activity of silica at the cellular level is sensitive to the composition and structure of surface functionalities and confirm that the biological response to silica is a surface originated phenomenon.

In vitro cleavage by asbestos fibers of the fifth component of human complement through free-radical generation and kallikrein activation.

Chrysotile and crocidolite fibers incubated in normal human plasma (NHP) generated from the C5 component of complement C5a-type fragments that stimulated polymorphonuclear leukocyte (PMN) chemotaxis. Absorption of NHP with antiserum against C5a totally abolished neutrophil chemotactic activity. Asbestos fibers also produced C5a small peptides in the presence of ethylene glycol bis(beta-aminoethyl ether) N,N,N'N'-tetraacetic acid (EGTA) but not ethylene diamine tetraacetic acid (EDTA). Activation of C5 was significantly inhibited when asbestos fibers were pretreated with iron chelators such as sodium dithionite (DTN), deferoxamine (DFX), or ascorbate (AA). Concentration-related inhibition of C5 activation was also observed when asbestos fibers were added concurrently to plasma in the presence of DFX, 1,3-dimethyl-2-thiourea (DMTU), a strong hydroxyl scavenger, or aprotinin (APR), a specific protease inhibitor. Further, chrysotile and crocidolite significantly increased plasma kallikrein activity. Data demonstrate that asbestos-induced C5 activation plays a role in inflammatory reactions characteristic of asbestosis through mechanisms involving iron ions, hydroxyl radicals, and oxidized C5-ike fragments. The ferrous ions present at the asbestos fiber surface trigger this activation and catalyze, via Fenton reaction, the production of hydroxyl radicals, which in turn convert native C5 to an oxidized C5-like form. This product is then cleaved by kallikrein, activated by the same asbestos fibers, yielding an oxidized C5a with the same functional properties as C5a.

Physicochemical properties of crystalline silica dusts and their possible implication in various biological responses.

The effect of grinding, heating, and etching was investigated on polymorphs of silicon dioxide exhibiting different biological responses. Diatomaceous earths were converted into cristobalite at 1000 degrees C. Dusts obtained by grinding crystalline minerals exhibited different micromorphology and a propensity to originate surface radicals which decrease in the sequence cristobalite --> quartz --> coesite --> stishovite. The production of surface radicals was suppressed by grinding in the presence of water. Thermal treatments selectively quenched the radicals and decreased surface hydrophilicity. Quartz treated with aluminum lactate exhibited higher surface acidity when compared with pure quartz, with a reduction in fibrogenicity. Etching by hydrofluoric acid smoothed the particles with loss of specific surface. Adsorption of water on three cristobalite dusts of different origin (ground mineral, ex-diatomite, heated quartz) indicated a loss in heated quartz (1300 degrees C) that was relatable to the corresponding reduction in fibrogenicity.

Calorimetric study on the solubilization of butanol by alkylphosphate and alkylphosphate-lecithin systems.

Microcalorimetric studies on alkylphosphate-butanol and alkylphosphate-butanol-lecithin systems were carried out as a first step to study the role of butanol (used as cosurfactant) in the formation of microemulsions. The enthalpy of solubilization; delta H, of the same amount of butanol (1.806 mol kg-1) in aqueous sodium monoalkyl-phosphates, with a hydrocarbon chain varying from 6 to 10 carbon atoms, was investigated as a function of alkylphosphate concentration. Measurements were performed in the presence and in the absence of lecithin. The enthalpy values measured upon addition of butanol to the mixtures were negative in all cases. Below the critical micelle concentration (CMC) of the alkylphosphates, the heats of butanol dissolution were found to decrease upon increasing the concentration of the alkylphosphate. This behaviour was related to the dissolution of butanol in water and to the formation of mixed butanol-alkylphosphate and butanol-alkylphosphate-lecithin micelles. Above the CMC essentially constant delta H values were found. The delta H measured may be the sum of simultaneous effects--heat of alcohol dissolution and the simple alkylphosphate micelle dissociation or alkylphosphate-lecithin mixed aggregate dissociation and the heat of mixed micelle formation. The delta H at the plateaus were linearly related to the corresponding CMC values of the alkylphosphates.