Occasional Exposure Research Articles

Structure-Activity Relationships in Allergic Contact Dermatitis. Part III. The Sensitizing Capacity of Substituted Phenanthrenequinones: A Quantum-Mechanical Approach

Nonterpenoid and diterpenoid phenanthrenequinones (PACs) have been found in the plant kingdom. Some of them occur in plants used in traditional Chinese medicine like Tan-Shen whereas others are constituents of orchids that are popular as ornamental plants. Case reports and our own observations in orchid nurseries suggest that some or even all of these PACs possess a distinct sensitizing potency. Occasional exposure (particularly of botanists) to field-grown orchids, as well as occupational contact with sawdust of PAC-containing tropical timbers, caused allergic contact dermatitis. However, experimental studies in guinea pigs to determine the sensitizing capacity of PACs have not been performed so far. Guinea pigs were sensitizied by a modified Freund's complete adjuvant method with four naturally occurring and 22 synthetic PACs in order to find out which and how many substituents at the carbons of the three rings of the PAC will influence the sensitizing power of the molecule. Subsequently, the lowest unoccupied molecular orbital (LUMO) coefficients were calculated to show whether a correlation exists between chemical reactivity and sensitizing capacity. Sensitizing capacity was found to be strong in two PACs, moderate in eight PACs, and weak in ten PACs. Five PACs were extremely weak in sensitizing capacity, and one PAC was completely negative. Two substituents on the left-hand carbons C-7 and C-8 of ring C were shown to be responsible for a strong sensitizing capacity. One methoxy group alone or three of them, especially when localized at C-5, decreased the sensitizing capacity to moderate. Substitution with a methoxy group at C-3 and/or at C-2 of the quinonoid ring itself (ring A) led to a weak sensitizing capacity. The ortho-quinones 1,2-PAC and 9,10-PAC were also weakly sensitizing. In fact, LUMO coefficient calculations corroborated a good correlation between chemical reactivity and sensitizing capacity. Substitution with methoxy groups at C-7 and/or at C-8 of ring C of 1,4-phenanthrenequinone increases the LUMO coefficients at the 2,3 double bond of ring A and thus facilitates nucleophilic substitution of protein nitrogen or sulfur nucleophiles at this electron-deficient double bond. The four naturally occurring PACs that were investigated--cypripedin, denbinobin, annoquinone-A, and latinone--do not fulfill these criteria and are thus only weak sensitizers. However, as-yet-unstudied phenanthrenequinones occurring in plants or trees and having no substituents at C-2 or C-3 of the quinonoid ring must be considered potentially strong allergens.

Behavioral and electrophysiological evidence for volatile sex pheromones in Parcoblatta wood cockroaches.

Species within the cockroach genus Parcoblatta are sexually dimorphic for wing length; females have reduced wings and are flightless, while males have long wings that are used in flight. We predicted that Parcoblatta females would release a volatile sex pheromone to attract the more mobile males. Nymphs of the broad wood cockroach, P. lata, and the Caudell's wood cockroach, P. caudelli, were collected in forested areas in North Carolina, USA, and reared in the laboratory for observations of sexual behavior and for pheromone analysis. After several days of sexual maturation, virgin females of both species exhibited distinct calling behaviors. In females of P. lata, calling commenced 6 days after adult emergence. Under a light-dark photoperiod regime, calling behavior in both species was restricted to the scotophase. Calling consisted of a repeated pattern of raising and lowering the abdomen with occasional exposure of the genital vestibulum. To test whether calling behavior is associated with the release of pheromone, volatiles from calling and noncalling females were collected on Super-Q and tested by electroantennogram (EAG) and behavioral assays. Volatile collections from calling females elicited higher male-specific EAG responses than collections from noncalling females of the same physiological stage. In an olfactometer choice test (Y-tube), males preferred volatiles from calling females over those from noncalling females. To determine the anatomical source of the pheromone, solvent extracts of various body parts were analyzed by EAG. The first through seventh tergites were the only body parts that elicited male-specific EAG responses in both species. In P. lata, the activity of the extract increased from 1- to 7-day-old females, but was lower in mated than in virgin females of the same age. The putative pheromone gland appears to consist of numerous class-3 secretory units, each composed of a secretory cell connected to a cuticular pore via a tubular duct. We conclude that female P. lata and P. caudelli produce ex-specific volatile pheromones that are emitted during calling behavior.

Association between exposure to environmental tobacco smoke and the development of acute coronary syndromes: the CARDIO2000 case–control study

Objective: To investigate the association between environmental tobacco smoke (ETS) exposure (at least 30 minutes a day) and the risk of developing acute coronary syndromes (ACS). Design and setting: The...

Effectiveness of a medical surveillance program for the prevention of occupational asthma caused by platinum salts: A nested case-control study

Background: Exposure reduction has proven to be effective in the prevention of occupational asthma. Few data are available on the effectiveness of secondary prevention programs, including medical examinations and removal of workers from exposure sources after detecting symptoms or signs indicative of a beginning disease. Objective: We sought to assess the effectiveness of a medical surveillance program in workers with exposure to platinum salts. Methods: A nested case-control study was performed in 14 workers of a catalyst production plant whose skin prick test (SPT) responses to platinum salt converted from negative to positive during a 5-year prospective cohort study with yearly medical examinations and 42 matched control subjects from the plant who did not experience SPT response conversion. With the exception of 2 subjects, the workers showing SPT response conversion were removed completely from exposure sources and followed for up to 42 months. Results: Work-related new symptoms were reported by 9 of the 14 subjects, and new symptoms without relation to work were reported by 3 subjects at the time of SPT response conversion. Symptoms were not accompanied by a change in FEV1 or bronchial responsiveness to histamine. Symptoms resolved after transferral, but occasional shortness of breath or wheeze persisted in 4 subjects. SPT reactions decreased or became negative in all workers after complete removal but remained unchanged in a craftsman with ongoing occasional exposure to contaminated materials. Conclusion: Although no randomized intervention was performed, this study proves the effectiveness of a medical surveillance program for the prevention of occupational asthma caused by platinum salts. (J Allergy Clin Immunol 2001;107:707-12.)

How does oxygen inhibit central metabolism in the obligate anaerobe Bacteroides thetaiotaomicron.

The molecular basis of obligate anaerobiosis is not well established. Bacteroides thetaiotaomicron is an opportunistic pathogen that cannot grow in fully aerobic habitats. Because microbial niches reflect features of energy-producing strategies, we suspected that aeration would interfere with its central metabolism. In anaerobic medium, this bacterium fermented carbohydrates to a mixture of succinate, propionate and acetate. When cultures were exposed to air, the formation of succinate and propionate ceased abruptly. In vitro analysis demonstrated that the fumarase of the succinate-propionate pathway contains an iron-sulphur cluster that is sensitive to superoxide. In vivo, fumarase activity fell to < 5% when cells were aerated; virtually all activity was recovered after extracts were chemically treated to rebuild iron-sulphur clusters. Aeration minimally affected the remainder of this pathway. However, aeration reduced pyruvate:ferredoxin oxidoreductase (PFOR), the first enzyme in the acetate fermentation branch, to 3% of its anaerobic activity. This cluster-containing enzyme was damaged in vitro by molecular oxygen but not by superoxide. Thus, aerobic growth is precluded by the vulnerability of these iron-sulphur cluster enzymes to oxidation. Importantly, both enzymes were maintained in a stable, inactive form for long periods in aerobic cells; they were then rapidly repaired when the bacterium was returned to anaerobic medium. This result explains how this pathogen can easily recover from occasional exposure to oxygen.

376 Pigeon Fancier's Lung (PFL) by an occasional exposure to pigeons

376 Pigeon Fancier's Lung (PFL) by an occasional exposure to pigeons

A case-control study of lung cancer among refinery workers.

This case-control study examined the relationship between lung cancer and the work histories of male employees at a large Texas refinery. The study included 112 lung cancer deaths observed between 1946 and 1987 and 490 matched controls. Employment histories were obtained from personnel records, and smoking information was available from medical records. Both stratification methods and conditional logistic regression were used in data analyses. Overall employment in four general job categories (administrative, engineering/laboratory, process, maintenance/mechanical) was not associated with lung cancer mortality. Results by hire period (< 1940, 1940+) showed that workers hired into process jobs before 1940 had a nonsignificantly elevated odds ratio (OR) of 1.71 (95% confidence interval [CI] = 0.85-3.45) compared with nonprocess workers hired before 1940. Among process workers hired before 1940, there was a significant trend toward increasing OR with increasing duration of employment in process jobs, and the association with lung cancer was strongest among smokers in the highest duration category of 30+ years (OR = 2.98, 95% CI = 1.07-8.31). Latency analyses of process workers hired before 1940 indicated that their lung cancer risk had peaked between 30 and 50 years since first employment. Definitive statements about causal factors are limited because results among process workers were based on small numbers of subjects in some exposure categories, and there was no information on specific workplace exposures. The OR for maintenance/mechanical jobs after adjustment for smoking was 1.00 (95% CI = 0.55-1.82). Furthermore, there was no pattern in relation to duration of employment in maintenance/mechanical jobs. The results from this study do not support the hypothesis that work in maintenance/mechanical jobs increases lung cancer risk. On the basis of analyses in this study, it is unlikely that asbestos exposure contributed to excess lung cancer mortality. Additional analyses were conducted for specific maintenance jobs with potential exposure to asbestos and by duration in jobs with occasional or routine asbestos exposure. No significant increase in lung cancer was found in any subgroup. Furthermore, there was no significant trend toward lung cancer risk in relation to duration of employment in jobs with asbestos exposure.

Genetic variation and clonal structure in the scleractinian coral Pocillopora damicornis in the Ryukyu Archipelago, southern Japan

Samples of the scleractinian coral Pocillopora damicornis were collected from six sites located around four islands in the Ryukyu Archipelago, southern Japan, and subjected to allozyme electrophoresis. Seven polymorphic loci were examined for their allelic patterns. The ratio of observed to expected genotypic diversity (0.30 < G o :G e < 0.64), the ratio of the observed number of genotypes to the number of individuals (0.47 < N g :N i < 0.75), and deviations from Hardy–Weinberg equilibrium indicated that asexual reproduction plays a major role in the maintenance of established populations. However, populations were not completely dominated by a single or a few clones, and most clones were represented by only a few individual samples. The high frequency of typhoons in the region suggests that, in P. damicornis, fragmentation caused through occasional exposure to powerful waves is a major mode of asexual reproduction, but asexual production of planulae may also be contributing to the maintenance of populations. A significant genetic differentiation (F ST) was found between the six populations examined (0.027 < F ST < 0.092, average F ST = 0.056). The moderate gene flow is discussed according to characteristics of the larval stage of the species, and to circulation patterns in the region.

Occupational hygiene in biowaste composting

Source-separated biowastes from the Helsinki Metropolitan Area have been composted in open air windrows at Ammas suo, the Helsinki regional landfill in Espoo (Finland). The most significant problem encountered in the early stages of the process has been the formation of rancid odor causing human discomfort. The offensive odor was mainly due to car boxylic acids. A total of 110 organic compounds were detected in volatile emissions from windrow composts with an integrated sensory and instrumental method. Occasionally the temperatures in the windrows exceeded 80°C. Bacterial measurements also revealed substantial populations of bacte ria at 75°C. The concentrations of airborne microbes and endotoxins were highest during the crushing of fresh biowaste and the turning of compost, and were relatively high in sum mer and when windrows were dry. The most common fungi in the air were Aspergillus and Penicillium. Dust concentrations were consistently low. The concentrations of microbes were never so high as to constitute an acute health hazard from the occasional exposure. Continuous exposure to such concen trations nevertheless increases the risk of illness. The time, neccessary for the compost to become hygienic improved from four months to four weeks during the project. Drum composting was also tested and was found to be an alternative approach to treating organic wastes. Emissions from the drum composting were low compared to open air composting.

A prospective study of passive smoking and coronary heart disease.

Several epidemiological studies have suggested an association of passive smoking with coronary heart disease (CHD). However, few studies have taken account of exposure to passive smoking in the workplace. Additionally, several studies have been unable to control for the full range of potential confounding factors. We examined prospectively the relationship of passive smoking with risk of CHD in a cohort of women. The study was carried out in an ongoing prospective cohort of US female nurses, in whom we assessed exposure to passive smoking at home and at work as well as duration of years spent living with someone who smoked regularly. We studied 32046 women 36 to 61 years of age in 1982 who had never smoked and were free of diagnosed CHD, stroke, and cancer. During 10 years of follow-up (1982 to 1992), 152 incident cases of CHD (127 nonfatal myocardial infarction and 25 fatal CHD) occurred. Compared with women not exposed to passive smoking, the relative risks of total CHD-adjusted for a broad range of cardiovascular risk factors-were 1.58 (95% CI, 0.93 to 2.68) among those reporting occasional exposure and 1.91 (95% CI, 1.11 to 3.28) among women reporting regular exposure to passive smoking at home or work. There was no relation apparent between duration of living with a smoker and risk of CHD. Despite the fact that exposure to passive smoking was assessed by self-report and only at baseline (as well as other limitations), these data suggest that regular exposure to passive smoking at home or work increases the risk of CHD among nonsmoking women.

The Cometary Activity of Chiron: A Stratigraphic Model

A theoretical model of a comet nucleus composed of H2O ice, a highly volatile ice, and nonvolatile material is used to simulate the recently observed comet-like activity of minor planet Chiron. It is found that even at Chiron's range of heliocentric distances, a continuous low level of activity can be sustained by the sublimation and diffusion of CO and/or CH4ices beneath a water ice and dust mantle and would be sufficient for possible emission of any loose submicrometer H2O ice grains. Due to Chiron's large size this continuous, low level gas flux can result in a significant loss of mass that can produce comet-like activity. The receding volatile ice never reaches an equilibrium depth but continues to recede slowly with time. The gas diffusing through the H2O ice mantle also decreases slowly with time due to the increasing mantle thickness. The mantle keeps the volatile ice interface nearly isothermal throughout an orbit after the first few orbits. This seems to explain the lack of correlation of outburst activity with heliocentric distance as is observed for most comets if Chiron typically contains a large fraction of water ice and if the water ice possesses sufficient strength to resist blowoff. We attempt to show that several processes suggested as a trigger for the apparently stochastic outbursts are not possible such as simple accumulation of highly volatile molecules, impacts, or thermal cracking of an H2O crust. We speculate that the outbursts may be caused by occasional exposure of more active regions on an object of high obliquity. The possible influence of impacts and temperature induced stress cracks on outbursts is discussed. Our results are compatible with previous findings that Chiron must have been inserted into its present orbit very recently.

Lower and lower Middle Pennsylvanian coal palynofloras, southwestern Virginia

Lower and lower Middle Pennsylvanian coals, recovered from an exploratory drilling program in southwestern Virginia, were analyzed for their palynomorph content. Results show them to be dominated by spores produced by arboreous lycopsids. Lycospora pellucida and Lycospora pusilla generally are the most common species, with others, namely Lycospora granulata, L. micropapillata and Lycospora orbicula being locally abundant. Densosporites, Cristatisporites, Radiizonates and Cingulizonates, representing small lycopsids, and Granulatisporites, produced by small ferns, and perhaps some pteridosperms typically are sub-dominant taxa. The recovered palynofloras are similar in overall composition making individual coal bed identification and correlation very difficult, if not impossible. However, the introduction and extinction of a few forms do assist the correlation of packages of strata, on both an intra- and interbasinal scale. Dictyotriletes bireticulatus is first observed in basal Lee Formation strata, at about the level of the Cove Creek coal bed. Radiizonates aligerans and R. striatus also appear more abundantly at this level, although some forms have been observed in older, Pocahontas Formation coals. This level essentially coincides with the Namurian C/Westphalian A boundary, based on plant megafossil evidence. Laevigatosporites minor, L. vulgaris, Endosporites globiformis, E. zonalis and Granasporites medius are first seen consistently just above the Sewell coal bed. Radiizonates aligerans, R. striatus and Densosporites irregularis are last seen in the early Middle Pennsylvanian, at about the level of the Splash Dam coal bed. Schulzospora rara occurs throughout Early and early Middle Pennsylvanian strata, and is last seen in the Manchester coal. The Manchester is directly overlain by the Betsie Shale, a widespread marine unit; the base of the Betsie marks the Westphalian A/B contact. When compared with palynomorph assemblage zonations published for the Western Interior, and Eastern Interior Basins, Early and early Middle Pennsylvanian palynofloras from the Central Appalachian Basin compare most favorably with early Morrowan strata. Analysis of bench samples indicates that Lycospora typically dominates basal and middle portions of Early and early Middle Pennsylvanian coals. More terminal layers often contain higher percentages of Granulatisporites (and related trilete, sphaerotriangular genera, e.g. Lophotriletes, Acanthotriletes, Deltoidspora) and Densosporites (and related trilete, crassicingulate genera, e.g. Cristatisporites, Cingulizonates, Radiizonates). This temporal change is consistently observed and may primarily reflect a water table change within the paleomires from consistently high (covered with water or at least water-logged most of the time) to intermittently low (occasional substrate exposure).

Effects of Blade Bending on Aerodynamic Control of Fluctuating Loads on Teetered HAWT Rotors

Active aerodynamic control, in the form of closed-loop actuation of blade-tip ailerons or all-moveable blades, is investigated as a means of increasing the structural fatigue life of HAWT rotors. The rotor considered is upwind and teetered, with two blades of diameter 29.2 m., fiberglass construction and other properties representative of modern light-weight construction. The paper begins with a review of prior work which studied the problem for an essentially rigid structure. For that and the present research, two loading conditions were invoked: exposure to a Rayleigh distribution of operating winds with vertical shear and a 15 percent superimposed spectrum of turbulence; and occasional exposure to 62 m/s hurricanes. Accounted for herein is the effect of flatwise bending flexibility on the loads spectra of root flatwise bending moment, thrust, and torque (both open loop and closed loop). Using Miner’s rule, the moments are converted to fatigue lives. With aerodynamic control, RMS flatwise moments for the flexible blade in turbulence are found to be less than 1/2 of those without control. At a fixed blade weight of 540 kg when hurricane loads are added, the aileron-controlled blade is “designed” by that limit-load condition. In contrast, the all-moveable blade can be feather controlled in the high wind so that its life is dominated by turbulent loads. Simplified fatigue analysis permits weight reductions to be estimated which yield controlled blades capable of 30 years’ operation with a safety factor of 11. The resulting weights are about 400 kg for the aileron-controlled blade, and 230 kg for the all-moveable blade. However, such light-weight rotors require attention to other design considerations, such as start-stop cycles. Apart from limit loads, the methods of analysis in this paper are linearized (locally for aerodynamic loads). It follows that the results are more likely to be meaningful in terms of comparative, rather than absolute, values of fatigue life and weight.

Lung function in children and adolescents with occasional exposure to environmental tobacco smoke.

We investigated the effects of occasional exposure to environmental tobacco smoke (ETS) on lung function in children. A total of 317 healthy 12- to 15-yr-old nonsmoking children and adolescents, living in households in which none of the adults were active smokers, were selected for the present analysis. The urinary cotinine:creatinine ratio (CCR) was taken as the biologic indicator of exposure, and children were classified according to CCR quartiles. The ratio between FEV1 and FVC (FEV1/FVC) and both early (peak expiratory flow [PEF]) and midexpiratory flow rates (FEF25-75) were lower in children with higher CCR values. In percent terms, the decrease in adjusted lung function for children belonging to the second, third, and fourth quartiles in comparison with those in the first quartile was -1.37, -2.12, and -1.94 for FEV1/FVC (p for trend = 0.012); 0.98, -3.31, and -4.54 for PEF (p for trend = 0.024); and -0.05, -4.85, and -6.13 for FEF25-75 (p for trend = 0.022), respectively. The effects remained significant when possible confounding by father's education and urinary creatinine level had been taken into account, and when children whose parents' smoking status may have been misclassified were excluded. This study suggests an adverse effect on lung function from even low-level exposure to ETS among nonsmoking children living with reportedly nonsmoking parents.

Hazard from impulse noise: Problems and prospects

Research findings continue to challenge the adequacy of existing impulse noise standards while consensus on a better formulation remains elusive. It is generally accepted that frequency weighting (reducing contribution of low frequencies) would be appropriate for impulse noise standards. However, data now present standards with twin problems which are opposite in character. On the one hand, the ear can be destroyed by intense exposures containing little energy (less than 10 J/m2) [Hamernik etal., J. Acoust. Soc. Am. 81, 1118–1129 (1987); Price and Wansack, J. Acoust. Soc. Am. 86, 2185–2191 (1989)]. Conversely, the ear can also tolerate immense amounts of energy at high intensities (≳100 kJ/m2) [Johnson and Paterson, Proc. 1992 Hearing Conserv. Conf. 103–106 (1992)]. A mathematical model of hearing hazard being developed [Price and Kalb, J. Acoust. Soc. Am. 90, 219–227 (1991)] promises to handle this complexity by incorporating a nonlinear stapes as well as middle ear muscle contractions into a hazard assessment, which is based on calculated basilar membrane displacements. Among other things, the model suggests that occasional exposure to intense impulses may be responsible for much of both occupational and nonoccupational noise-induced hearing loss.

Toluene diisocyanate induced asthma: outcome according to persistence or cessation of exposure.

Sixty patients with occupational asthma due to exposure to toluene diisocyanate (TDI) were re-evaluated, five years after the initial diagnosis had been confirmed by a specific bronchial provocation challenge. During both examinations the severity of asthmatic symptoms and the need for antiasthma treatment were graded and lung function tests, measurement of airway responsiveness to methacholine (PD15), and skin tests with common inhalant allergens were carried out. The evolution of the disease was established on the basis of the increase or decrease in asthmatic symptoms, requirements for medication, and FEV1 and PD15 methacholine between the two examinations. At follow up 17 patients (group A, 28.3%) had carried on working in the same environment after relocation to jobs with only occasional exposure to TDI; 15 of them used protective respiratory devices. The remaining 43 (group B, 71.7%) avoided further inhalation of TDI by moving to another sector. Group A showed a significant decrease in FEV1 and PD15 methacholine and significant increases in the severity of symptom score and requirement for medication; 13 subjects (76.5%) were worse, four (23.5%) were stable, and no one had recovered or improved. Group B showed significantly less severe symptoms and a threefold increase in PD15 methacholine; 12 subjects (28.2%) totally recovered, 10 (23.2%) improved, 16 (37.2%) were stable, and five (11.6%) were worse. In group B the duration of exposure to TDI and of symptoms before the initial diagnosis delineated the patients who recovered from those who did not improve; intermediate values in these features characterised the subjects who improved but did not recover. It is inferred that complete removal from exposure is the only effective way of preventing deterioration in patients with occupational asthma due to TDI. Early diagnosis and early removal from exposure after the onset of asthma are important factors for a favourable outcome of the disease.

Early delayed hypersensitivity responses in tuberculin skin tests after heavy occupational exposure to tuberculosis.

The early (six hours) reaction to tuberculin skin testing was studied in 33 Indonesian hospital workers with frequent occupational exposure to M tuberculosis and compared with responses maximal at the usual time (48 hours) in factory workers, from the same locality but with only occasional occupational exposure, to determine the nature of the early reaction. The early reaction had the same general histopathological appearance as that seen in the conventional (48 hour) reaction, and both had an infiltrate consisting largely of T lymphocytes and macrophages. The cell densities were lower in the six hour reactions, but the relative concentration of macrophages was greater in the earlier response. These histometric measurements suggested that the six hour reaction was an accelerated delayed hypersensitivity reaction. Moreover, the absence of a specific IgE response or of particulate masses of Ig or complement, made it unlikely an anaphylactoid or Arthus-type reaction could have been responsible. It is concluded that those with frequent occupational exposure to M tuberculosis have larger numbers of circulating T cells reactive with mycobacterial antigens, so that the development of the skin test response to tuberculin is less dependent on "by-stander" cell infiltration to mediate the delayed hypersensitivity reaction than the reactions in those with less intense and less frequent natural exposure. The skin test response maximal at six hours is probably a hyperimmune reaction to an antigen recognised by T cells.

Occult Exposure to Asbestos in Steel Workers Revealed by Bronchoalveolar Lavage

To investigate the asbestos burden in a steelplant environment, we counted asbestos bodies (ABs) in the bronchoalveolar lavage fluid (BALF) of 65 steel workers who had retired during the previous 5 y. They had worked for at least 15 y in the same area of the plant (coke oven or blast furnace) as maintenance or production workers. On the basis of occupational anamnesis, 28 had occasional past professional exposure to asbestos; the remaining 37 workers denied any contact with asbestos. A total of 54 white-collar workers who had no occupational exposure to asbestos were included in the study as controls. An increased prevalence and concentration of ABs was found in the BALF of steel workers. Electron microscopy and EDAX analysis of AB from steel workers revealed that the core fibers were mainly amphiboles. More ABs were found in the BALF of maintenance workers than in production workers. However, the BALF from steel workers who denied any contact with asbestos revealed an increased AB burden v. controls. This demonstrates that steel workers may be subject to an occult exposure to amphiboles in the steelplant environment.

Skin Typing, Sun Exposure, and Sunscreen Use in a Population of Japanese

Distribution of Japanese skin types (JSTs), sun-exposure habits, and sunscreen use were surveyed in 379 new outpatients. The largest number of subjects belonged to JST class J-II (65%), J-I was second (24%), and J-III was third (11%). Eighty-eight percent of those studied had occasional or habitual sun exposure during the summer, and many were exposed for more than three hours per exposure day (80% of those with occasional exposure; 62% of those with habitual exposure). More younger persons had occasional sun exposure than older persons. More males had habitual sun exposure than females. Sunscreens were used by 41% of the subjects, but 77% of these used them without accurate understanding of the definition of the sun protection factor. More J-I subjects used sunscreens than J-II and J-III subjects. More females than males used them.

A prospective study of cow's milk allergy in exclusively breast-fed infants. Incidence, pathogenetic role of early inadvertent exposure to cow's milk formula, and characterization of bovine milk protein in human milk.

A cohort of 1,749 newborns in the municipality of Odense were followed prospectively for the development of cow's milk allergy (CMA) during their first year of life. Altogether 39 fulfilled the criteria for CMA (2.2%). Out of the 39 infants, 17 developed symptoms of CMA during breast-feeding, in all cases before the age of 3 months. Nine of these were solely breast-fed at the time of diagnosis, giving a one year incidence of CMA in exclusively breast-fed infants of 0.5% (9/1,749) in a study population with a frequency of exclusive breast-feeding of 52% at 3 months of age. None of the infants had signs of CMA in the neonatal period. Review of records from the newborn nursery revealed that all 9 infants had been exposed to cow's milk formula in amounts corresponding to approximately 0.4-3.0 g of beta-lactoglobulin (BLG) during the first three days of life. Human milk samples were analyzed by enzyme-linked immunosorbent assay (ELISA) for the content of bovine BLG. Detectable amounts (0.5-45 ng/ml) were found in 3/9 samples of human milk against which the infants reacted clinically. Analysis of the size distribution by high pressure liquid gel permeation chromatography in combination with ELISA indicated a molecular weight of BLG corresponding to that of monomeric BLG (18 kD). Possibly early inadvertent and occasional exposure to cow's milk proteins may initiate sensitization in predisposed neonates. Subsequent exposure to minute amounts of bovine milk proteins in human milk may act as booster doses eliciting allergic reactions.