Evaluation of the exposure, dose-response and fate in the lung and pleura of chrysotile-containing brake dust compared to TiO2, chrysotile, crocidolite or amosite asbestos in a 90-day quantitative inhalation toxicology study - Interim results Part 1: Experimental design, aerosol exposure, lung burdens and BAL.

This 90-day repeated-dose inhalation toxicology study of brake-dust (BD) (brakes manufactured with chrysotile) in rats provides a comprehensive understanding of the biokinetics and potential toxicology in the lung and pleura. Exposure was 6 h/d, 5d/wk., 13wks followed by lifetime observation (~20 % survival). Control groups included a particle control (TiO2), chrysotile, commercial crocidolite and amosite asbestos. Aerosol fiber distributions of the chrysotile, crocidolite and amosite were similar (fibers L > 20 µm/cm3: chrysotile-Low/High 29/72; crocidolite 24; amosite 47 fibers/cm3; WHO-fibers/cm3: chrysotile-Low/High 119/233; crocidolite 181; amosite 281 fibers/cm3). The number of particles/cm3 in the BD was similar to that in the chrysotile, crocidolite & amosite exposures (BD 470-715; chrysotile 495-614; crocidolite 415; amosite 417 particles/cm3). In the BD groups, few fibers L > 20 µm were observed in the lungs at the end of exposure and no fibers L > 20 µm at 90d post exposure. In the chrysotile groups, means of 204,000 and 290,000 fibers(L > 20 µm)/lung were measured at 89d. By 180d, means of 1 and 3.9 fibers were counted on the filter corresponding to 14,000 and 55,000 fibers(L > 20 µm)/lung. In the crocidolite and amosite groups mean lung concentrations were 9,055,000 and 11,645,000 fibers(L > 20 µm)/lung at 89d. At 180d the means remained similar with 8,026,000 and 11,591,000 fibers(L > 20 µm)/lung representing 10-13% of the total lung fibers. BAL determined the total number of macrophages, lymphocytes, neutrophils, eosinophils, epithelial-cells and IL-1 beta, TNF-alpha and TGF-beta. At the moderate aerosol concentrations used in this study, neutrophil counts increased ~5 fold in the amphibole asbestos exposure groups. All other groups and parameters showed no important differences at these exposure concentrations. The exposure and lung burden results provide a sound basis for assessing the potential toxicity of the brake dust in comparison to the TiO2 particle control and the chrysotile, crocidolite and amosite asbestos control groups. The BAL results provide an initial indication of the differential response. Part 2 presents the presentation and discussion of the histopathological and confocal microscopy findings in this study through 90 days post exposure.

Evaluation of the dose-response and fate in the lung and pleura of chrysotile-containing brake dust compared to TiO2, chrysotile, crocidolite or amosite asbestos in a 90-day quantitative inhalation toxicology study - Interim results Part 2: Histopathological examination, Confocal microscopy and collagen quantification of the lung and pleural cavity.

The interim results from this 90-day multi-dose, inhalation toxicology study with life-time post-exposure observation has shown an important fundamental difference in persistence and pathological response in the lung between brake dust derived from brake-pads manufactured with chrysotile, TiO2 or chrysotile alone in comparison to the amphiboles, crocidolite and amosite asbestos. In the brake dust exposure groups no significant pathological response was observed at any time. Slight macrophage accumulation of particles was noted. Wagner-scores, were from 1 to 2 (1 = air-control group) and were similar to the TiO2 group. Chrysotile being biodegradable, shows a weakening of its matrix and breaking into short fibers & particles that can be cleared by alveolar macrophages and continued dissolution. In the chrysotile exposure groups, particle laden macrophage accumulation was noted leading to a slight interstitial inflammatory response (Wagner-score 1-3). There was no peribronchiolar inflammation and occasional very slight interstitial fibrosis. The histopathology and the confocal analyses clearly differentiate the pathological response from amphibole asbestos, crocidolite and amosite, compared to that from the brake dust and chrysotile. Both crocidolite and amosite induced persistent inflammation, microgranulomas, and fibrosis (Wagner-scores 4), which persisted through the post exposure period. The confocal microscopy of the lung and snap-frozen chestwalls quantified the extensive inflammatory response and collagen development in the lung and on the visceral and parietal surfaces. The interim results reported here, provide a clear basis for differentiating the effects from brake dust exposure from those following amphibole asbestos exposure. The subsequent results through life-time post-exposure will follow.

Evaluation of the dose-response and fate in the lung and pleura of chrysotile-containing brake dust compared to chrysotile or crocidolite asbestos in a 28-day quantitative inhalation toxicology study.

This study provides an understanding of the biokinetics and potential toxicology in the lung and pleura following inhalation of brake-dust (brakes manufactured with chrysotile). The design included a 28-day repeated multi-dose inhalation exposure (6 h/d, 5 d/wk, 4 wks) followed by 28-days without exposure. Fiber control groups included a similar grade chrysotile as used in the brakes and a commercial crocidolite asbestos. Aerosol fiber distributions of the chrysotile and crocidolite were similar (fiber-length > 20 µm/cm3: Chrysotile-low/high 42/62; Crocidolite-low/high 36/55; WHO-fibers/cm3: Chrysotile-low/high 192/219; Crocidolite-low/high 211/255). The total number of aerosol particles/cm3 in the brake-dust was similar to that in the chrysotile (Brake-dust 710-1065; Chrysotile 532-1442). Brake-dust at particle exposure levels equal to or greater than chrysotile or crocidolite caused no indication of microgranulomas, epithelial hyperplasia, or fibrosis (Wagner score < 1.7) or changes in bronchoalveolar lavage (BAL) indices from the air control. Chrysotile BAL indices did not differ from the air control. Pathologically, there was low level of inflammation and epithelial hyperplasia, but no fibrosis (Wagner score ≤ 3). Crocidolite induced elevated neutrophils and cell damage (BAL), persistent inflammation, microgranulomas, and fibrosis (Wagner scores 4) which persisted through the post exposure period. Confocal microscopy of snap-frozen chestwalls showed no difference between control, brake-dust and chrysotile-HD groups or in thickness of visceral or parietal pleural. The crocidolite exposure resulted in extensive inflammatory response, collagen development and adhesions between the visceral and parietal surfaces with double the surface thickness. These results provide essential information for the design of a subsequent subchronic study.

Evaluation of the fate and pathological response in the lung and pleura of brake dust alone and in combination with added chrysotile compared to crocidolite asbestos following short-term inhalation exposure.

This study was designed to provide an understanding of the biokinetics and potential toxicology in the lung and pleura following inhalation of brake dust following short term exposure in rats. The deposition, translocation and pathological response of brake-dust derived from brake pads manufactured with chrysotile were evaluated in comparison to the amphibole, crocidolite asbestos. Rats were exposed by inhalation 6h/day for 5 days to either brake-dust obtained by sanding of brake-drums manufactured with chrysotile, a mixture of chrysotile and the brake-dust or crocidolite asbestos. The chrysotile fibers were relatively biosoluble whereas the crocidolite asbestos fibers persisted through the life-time of the animal. This was reflected in the lung and the pleura where no significant pathological response was observed at any time point in the brake dust or chrysotile/brake dust exposure groups through 365 days post exposure. In contrast, crocidolite asbestos produced a rapid inflammatory response in the lung parenchyma and the pleura, inducing a significant increase in fibrotic response in both of these compartments. Crocidolite fibers were observed embedded in the diaphragm with activated mesothelial cells immediately after cessation of exposure. While no chrysotile fibers were found in the mediastinal lymph nodes, crocidolite fibers of up to 35 µm were observed. These results provide support that brake-dust derived from chrysotile containing brake drums would not initiate a pathological response in the lung or the pleural cavity following short term inhalation.

A South African database of samples analysed for the presence of asbestos

Background: Asbestos mining and other activities have left a legacy of environmental contamination. Asbestos was used in a large number of manufactured products but little is documented about the nature and location of these products. Compliance with asbestos regulations depends on accurate identification of the presence of asbestos. The National Institute for Occupational Health (NIOH) has been identifying asbestos for regulatory purposes since 2003. Objective: To analyse a database of samples submitted for asbestos analysis to the NIOH. Methods: Asbestos was identified using scanning electron microscopy and energy dispersive spectroscopy. The data were analysed using STATISTICA version 11. Results: From 2003 to 2012; 1514 samples were analysed. Asbestos was identified in 59.9 of the bulk samples and crocidolite was present in 45.4 of these. Information about samples containing asbestos; including their origin and associated activities; are described. Conclusions: Although asbestos is no longer mined or used in South Africa; workers remain at risk of exposure due to asbestos-containing materials which persist in the environment. Knowledge of these materials gained from routinely collected data may assist in the safe removal of asbestos and prevent further adverse health =effects

Trends in mesothelioma mortality rates in South Africa: 1995-2007.

OBJECTIVE: In 1984, South Africa had one of the highest mesothelioma rates in the world. The objective of this analysis was to calculate mesothelioma mortality rates in the South African population from 1995 to 2007. METHODS: Annual mortality data and midyear population estimates were used to compute mortality rates by age group and gender for each year. The WHO World Standard Population was used as the reference population to calculate age-adjusted rates. Poisson regression models were used to test for trends. RESULTS: In total, 2509 deaths due to mesothelioma were identified in the study period: 1920 in men and 588 in women. There were no significant trends in mesothelioma mortality rates: age-adjusted mortality rates fluctuated from 11 to 16 and from 3 to 5 per million per year for men and women, respectively. CONCLUSION: These mortality rates are much lower than expected, given the historical production and use of, and high exposure to, asbestos in South Africa. Possible reasons for this are discussed, including the effect of HIV which has been instrumental in reducing the life expectancy of South Africans in the last two decades. Asbestos-exposed individuals may not live long enough to develop mesothelioma. Competing causes of death need to be taken into account when constructing models to predict mesothelioma mortality rates.

Rock drills used in South African mines: a comparative study of noise and vibration levels.

OBJECTIVES: To compare the noise and vibration levels associated with three hand-held rock drills (pneumatic, hydraulic and electric) currently used in South African mines, and a prototype acoustically shielded self-propelled rock drill. METHODS: Equivalent A-weighted sound pressure levels were recorded on a geometrical grid, using Rion NL-11 and NL-14 sound level meters. Vibration measurements were conducted on the pneumatic, hydraulic and electric drills in accordance with the ISO5349-1 (2001) international standard on human exposure to hand-transmitted vibration, using a Brupsilonel and Kjaer UA0894 hand adaptor. PCB Piezo accelerometers were used to measure vibration in three orthogonal directions. No vibration measurements were conducted on the self-propelled drill. RESULTS: All four drills emitted noise exceeding 85 dB(A). The pneumatic drill reached levels of up to 114 dB(A), while the shielded self-propelled drill almost complied with the 85 dB(A) 8 h exposure limit. Vibration levels of up to 31 m s(-2) were recorded. These levels greatly exceed recommended and legislated levels. CONCLUSIONS: Significant engineering advances will need to be made in the manufacture of rock drills to impact on noise induced hearing loss and hand arm vibration syndrome. Isolating the operator from the drill, as for the self-propelled drill, addresses the problems of both vibration and noise exposure, and is a possible direction for future development.

Asbestos lung fibre concentrations in South African chrysotile mine workers.

Mesothelioma has not been found in South African chrysotile miners and millers despite decades of producing about 100000 tons of the mineral per year. One possible explanation for the scarcity or absence of the cancer may be a relative lack of contaminating fibrous tremolite, an amphibole that variably occurs with chrysotile ores. The fibre content in the lungs of nine former chrysotile mine workers was ascertained by transmission electron microscopy. Despite fairly long service in most cases (median 9.5 yr; range 32-4 yr) the concentrations of chrysotile fibres were relatively low: only two cases exceeded 1.14 million fibres/g dried lung. Tremolite fibre levels were even lower: less than 1 million fibres/g dried lung in all but one case. Tremolite fibre concentrations exceeded those of chrysotile in only two cases. These results support the contention that South African chrysotile is not heavily contaminated by tremolite.

Association between Chlamydia pneumoniae and atherosclerotic lesions.

There can no longer be any doubt that viable Chlamydia pneumoniae organisms are present in atherosclerotic lesions. Indeed, the endovascular presence of C. pneumoniae in coronary artery disease (CAD) is common. The fact that this lesion, which is the major cause of stroke, coronary heart disease ( CHD), peripheral vascular disease and aortic aneurysm, can no longer be regarded as sterile has prompted a good deal of study and speculation. Atherosclerotic lesions have been studied in detail, but until recently histological descriptions of the lesion have not included C. pneumoniae organisms. Reviews and analysis of the literature confirm the association between C. pneumoniae and atherosclerotic lesions and CHD. The possibility that C. pneumoniae plays a causal or contributory role in the development of atherosclerotic lesions has been debated. It is of major importance as there is already evidence that antibiotic therapy may be of clinical benefit in patients with CHD. Large clinical trials using antichlamydial agents have been embarked upon which may provide further evidence of a causal role for C. pneumoniae. The underlying mechanism of how C. pneumoniae contributes to lesions and the effect of antibiotic therapy on lesions remain unknown. The association between C. pneumoniae and atherosclerosis is reviewed. Particular attention is paid to the lesion itself and the presence of C. pneumoniae. Potential areas of study that may contribute to this rapidly expanding area of research is explored.

The pulvillus and empodium in Culex quinquefasciatus: visualization with the light microscope and a study of fine structure with the scanning electron microscope.

The empodia and pulvilli on each postarsus were examined in male and female Culex quinquefasciatus. Up to 160x magnification was required to see them clearly under the stereo light microscope but they were more readily visible under the compound light microscope as slide mounts at 100-200x magnification. Scanning electron micrographs of female and male pulvilli showed that they are either well developed (females) or inconspicuous (males) and that they consist of setal tufts composed of both pointed and trumpet-ended setae. The ultrastructure of the pulvilli is described and their possible function in oviposition is discussed.

Myocardial infarction associated with Chlamydia pneumoniae.

A 39-year-old black South African man with no recognised risk factors for coronary hart disease (CHD) except hypertension, died of a myocardial infarct (MI). The case was unusual because although hypertension is common, MI is rare in black South Africans. Serology indicated that the subject had previously had a Chlamydia pneumoniae infection. The primary lesion in the left anterior descending branch of the coronary artery was a ruptured atherosclerotic plaque in which C. pneumoniae was indentified by immunocytochemical, electron microscopic and polymerase chain reaction techniques. The organisms were detected in smooth-muscle cells, foam cells and interstitially, but not in adjacent unaffected tissue. C. pneumoniae DNA was also detected in the myocardium of the left ventricle in an area of the infarct. It is postulated that debris from the ruptured plaque was deposited in the muscle. The observations support the association between C. pneumoniae and CHD; for the first time the organism is identified in a lesion that ruptured and caused an MI.

Histological and ultrastructural findings suggesting an initiating role for Chlamydia pneumoniae in the pathogenesis of atherosclerosis.

AIMS: An association between Chlamydia pneumoniae and atherosclerosis is now well established. The finding of C. pneumoniae in atherosclerotic lesions has led to the hypothesis that this organism may have an aetiological role in atherogenesis. The implications of such a concept are enormous, but to date the pathological features of the lesion have not been examined in the light of this new hypothesis. This study was designed to determine the pathological basis of the association between C.pneumoniae and atherosclerotic lesions. METHODS: The pathological features of 50 atherosclerotic lesions from 50 different patients, in which C.pneumoniae had been demonstrated by immunocytochemistry and PCR techniques, were examined using light and electron microscopy techniques. In 20 cases the lesions were fatty streaks, 20 were fibro-atheroma lesions, and 10 were advanced, complicated lesions. RESULTS: Intimal smooth-muscle cells infected with C. pneumoniae exhibit vacuolation, loss of myofilaments, an increase in lipid, rupture and fragmentation. Macrophages phagocytose these muscle cell fragments, lipid and C. pneumoniae. Large numbers of extracellular C. pneumoniae organisms were identified in the central necrotic core, in areas of fibrosis, in areas of fragmentation of the internal elastic lamina, and in ceroid bodies. Neither pathological changes nor organisms were seen in the endothelium. CONCLUSIONS : C. pneumoniae infection of intimal smooth&hypen; muscle cells is accompanied by cytoplasmic alterations and damage. The fatty streak appears to be formed by a macrophage response to this muscle damage. C. pneumoniae is found in early, mature and advanced lesions. This is the first study of the pathology of atherosclerosis suggesting that the lesion be interpreted as an infective chlamydial granuloma.

Chlamydia pneumoniae in atheroma: consideration of criteria for causality.

AIMS: (1) To seek evidence of the existence of Chlamydia pneumoniae in a spectrum of atheromatous lesions in different types of arteries from individuals of different ages, using a polymerase chain reaction (PCR) assay supported by electron microscopy and immunocytochemistry; (2) to use electron microscopy to examine interactions between C pneumoniae and the cells present in the arterial tissue; (3) to assess the extent to which the data fulfil the criteria for causality. METHODS: At necropsy examination, 35 arterial specimens were taken from 25 subjects. The grade of atheroma was determined macroscopically and microscopically and the tissues coded and examined by the three techniques. RESULTS: Of the 35 specimens, 24 had macroscopic or microscopic atheromatous lesions of varying degree. Twenty two of the 35 specimens were examined by electron microscopy, C pneumoniae-like bodies being found in 11 (50%); seven specimens were examined by the immunocytochemical method, positive staining being detected in three; and all specimens were examined by the PCR technique, 15 (43%) being PCR positive. Overall, of the 24 specimens with lesions, 17 (71%) were positive by at least one of the three tests, whereas of the 11 specimens without lesions, only one was positive. The positive specimens comprised 10 of 19 aortas, three of six iliac arteries, and one coronary and one pulmonary artery. C pneumoniae was detected in four of six specimens in which there were early changes and in a 20 year old subject. Concerning the 25 subjects, of 17 who had atheromatous arteries, 14 (82%) were C pneumoniae positive and of the eight who had normal arteries, none was positive. CONCLUSIONS: There is a strong correlation between C pneumoniae and arterial atheromatous lesions. The organism may contribute to the disease process by damaging smooth muscle cells.

Death following exposure to fine particulate nickel from a metal arc process.

A man was taken ill suddenly while spraying nickel using a thermal arc process. He was relieved of his duties and sent home. His condition deteriorated and he was admitted to hospital with a diagnosis of pneumonia. Thirteen days after exposure he died. At post mortem examination the cause of death was determined to be shock lung or Adult Respiratory Distress Syndrome (ARDS). Reproduction of the conditions under which the man had operated the metal arc process produced nickel concentrations of 382.1 mg m-3 in the air next to the operator. Of this nickel, 64.6% was in the form of particles less than 1.4 microns in diameter; the majority being 50 nm in diameter. The total amount of nickel inhaled by the man, who operated the process for 90 min, was estimated to be nearly 1 g. The toxicity of the nickel is thought to be associated with the very fine particulate nature of the metal fume and the large amount inhaled. The importance of wearing adequate protective equipment while operating this metal arc process is stressed.

Primary hyperaldosteronism due to a functional black (pigmented) adenoma of the adrenal cortex.

The clinical and pathologic findings are reported in a case of primary hyperaldosteronism due to a functional black (pigmented) adenoma of the adrenal cortex. Cortical atrophy of the involved gland was present, the mechanism of which was obscure.

Fine needle aspiration of pediatric abdominal masses. Cytologic and electron microscopic diagnosis.

Fine needle aspiration (FNA) was performed under ultrasound guidance on 17 abdominal masses in 16 pediatric patients at Baragwanath Hospital. The aspirated cellular material was assessed by conventional cytomorphology and by electron microscopy (EM). A diagnosis of malignancy was rendered for all 15 tumors that were adequately sampled (88.2%); the remaining 2 masses yielded insufficient material for either light microscopy or EM. Cytologic cell typing (including the use of EM) was successful in 12 of the 15 tumors (80%) as compared with the histologic diagnosis. EM was in agreement with the initial cytologic diagnosis in eight tumors, but corrected the initial impression in four tumors. The tumors with adequate aspirates included nine nephroblastomas and single examples of neuroblastoma, hepatoblastoma, non-Hodgkin's lymphoma, rhabdomyosarcoma, renal carcinoma and malignant rhabdoid tumor. The last three were not accurately typed by cytology plus EM. These preliminary results suggest that FNA cytology with adjunctive EM could become a useful technique in the preoperative assessment of pediatric abdominal tumors.

Red or rufous albinism in southern Africa.

Red or rufous albinism is a rare type of oculocutaneous albinism described, but not as yet fully investigated, in Africa and New Guinea. Twelve rufous albino subjects from 10 families participated in this preliminary study. The prevalence of rufous albinism was found to be approximately one in 8,580 among school children in the negroid population. The combination of the unusual red skin colour, ginger to reddish hair colour, low susceptibility to sun damage, and minimal visual problems, in affected individuals, suggested that they form a group which is distinct from the brown and other types of albinism. The mode of inheritance was found to be recessive. Tyrosinase assays showed that rufous albinos are tyrosinase positive and on electron microscopy studies normal melanosomes and melanocytes were observed in hair bulbs and skin. Visual evoked potential testing did not show the gross decussation abnormalities of the optic pathway detected in other types of albinism. Rufous albinism might be at one end of the spectrum of types of oculocutaneous albinism and, because affected people have such mild symptoms, their inclusion in this group might be debatable.

Demyelinisation in the spinal cord of vitamin B12 deficient fruit bats.

1. Vitamin B12 deficiency induced in the fruit bat by a combination of dietary deprivation and exposure to nitrous oxide (N2O) is accompanied by profound neurological impairment, thus providing an experimental model for the study of vitamin B12 neuropathy. 2. Electron microscopy of the spinal cord of vitamin B12 deficient bats shows marked changes in the myelin of the posterior columns in the form of distension, separation and vacuolation of myelin lamellae similar to the changes described in the dietary induced B12 deficient monkey model. 3. No equivalent change occurred in bats exposed to N2O and supplemented with vitamin B12.