# Latex allergen in respirable particulate

air pollution

P. Brock Williams, PhD, Martin P. Buhr, PhD, Richard W. Weber, MD, Micheal A. Volz, MD, Jerald W. Koepke, MD, and John C. Selner, MD Denver, Colo.

Objective."Urbanairsamples contain numerous irregularrespirableblackparticles, which may be airborne tire

fragments. A major component oftiresis natural latex.Proteins ofnatural latex can act as adjuvants and as antigens capable ofelicitingimmediate hypersensitivity, making theirpresence inparticulate airpollution an important clinical issue. Methods:Particulate airpollutants werecollected by volumetric sampling devices and characterizedby optical microscopy, chemical solubility tests,and mass"spectrometry.Extracts ofrubber tire

fragments weretested

for elutable latexantigens by antibody inhibition assays. Results:Identification oflatex in airsamples and milled materialfrom automobile tireswas supported by mass spectrometry resultsand wasfurther confirmed byphysical appearance and chemical solubility studies. Competitive immunoassay confirmed thepresence ofextractable latexantigensfrom rubber tire fragments. Conclusions:Latex antigens are extractable from rubber tire

fragments, which are abundant in urban airsamples. Given the adjuvant andsensitizing effectsoflatex, these airborneparticles could contribute, through directand indirectmechanisms, to the increasein both latex sensitization and asthma. The impact oftheseparticles should be considered in the issueof morbidity and mortality ratesassociated with respiratorydiseasesand airpollution. (J ALLERGYCLIN

IMMUNOL1995;95.'88-95.) Key words:Latex, rubber tires;airpollution, asthma

Natural latex is used in a wide variety of products that have become part of our everyday environment. The main source of natural latex is the sap of the tropical rubber tree, Hevea brasiliensis, and over 7 million metric tons are produced annually? Native latex coagulates by forming polymers of cis-l,4 isoprene several thousand units in length.2 Proteins comprise about 2% of the total solids of uncoagulated latex? Two of these proteins involved in the polymerization of isoprene units have been implicated in hypersensitivity reactions to latex products.4,5 Sensitivity to latex had not been considered a major clinical problem until recent years. The

From the AllergyRespiratoryInstituteofColoradoand UniversityofColoradoHealth SciencesCenter,Departmentof Immunology,Denver. ReceivedforpublicationMar.4, 1994;revisedJune 16, 1994; acceptedforpublicationJune 23, 1994. Reprintrequests:P.BrockWilliams,PhD,AllergyRespiratory Institute of Colorado, 5800 East EvansAve., Suite 100, Denver,CO 80222. Copyright© 1995byMosby-YearBook,Inc. 0091-6749/95$3.00+ 0 1/1/58674

88 marked increase in the use of latex products, particularly in the health care industry, has likely contributed to the increase in latex sensitization.6 Clinical reactions vary from skin rashes and mild rhinitis to more severe bronchial asthma and lifethreatening anaphylactic reactions.7,8Risk factors identified include frequency of exposure and atopy.9 Recent studies indicate that up to 14% of health care workers are affected, as well as 64% of patients with spina bifida who undergo repeated surgery and catherization.1°,11 Latex sensitization ofnearly 10% has been reported in atopic individuals undergoing routine aeroallergen skin testing.9 Relatively low concentrations of respirable particulate matter have been significantly associated with increases in daily mortality rates, acute bronchitis, and hospital visits for treatment of lower respiratory tract symptoms.12-~5 Both morbidity and mortality rates for respiratory asthma have increased dramatically, particularly in urban areas throughout the world,a6-22Children seem to be at particular risk, and particulate air pollution of 2 to 10 ~m has been implicated.2329 A significant portion ofparticulate air pollutionJ ALLERGYCLIN IMMUNOL Williams et al. 89

VOLUME 95, NUMBER 1, PART I

in urban areas may consist of small irregularly shaped black particles. The most likely source of these particles is the abrasion of rubber tires on road surfaces. Tires are made of various mixtures of natural and synthetic rubber along with sulfur, carbon black, and zinc oxide. This results in a flexibleyet sturdy material that can withstand heat and friction well.3° However, tire wear releases particles of varying size, which may add to atmospheric pollution burden. In this study we confirmed that a large number ofrespirable tire fragments are found in urban air. We investigated the hypothesis that these fragments contain latex proteins. These particles could be partially responsible for the increase in latex sensitization, as well as the respiratory problems associated with air pollution.


### METHODS Physical and chemical characterization of particles
Particulate samples were collected by three different procedures: rotary impaction sampling (Rotorod; Sampling Technologies Inc., Los Angeles, Calif.); highvolume air samplingwith a PM~osamplerequippedwith

an inlet that discriminated against particles larger than 10 Ixm (Sierra Instruments, Monterey, Calif.); and passive gravimetric air sampling with glass plates (20 × 20 cm) coated with silicone grease. The impaction sampler was stationed 7.4 m above ground level, 48 m from a four-lane, moderately travelled road. The PMlo samplerswere located attwo differentColorado Department of Health sampling stations in the Denver metropolitan area. Rotorod samples were stained with Calberla's solution to facilitate pollen and particulate counting.31 The glass plates were exposed at ground level 30 m from roadside air for 6 hours, and samples

were harvested by scraping with a flat surgical blade. The size of the particles was determined with an optical microscope and a 45× achromatic lens. The eyepiece (10x) of the microscope was fitted with a graduated reticle to permit measurement of particle sizes. The reticle was calibratedwith a 22mm glass slide

cover. Particle sizes were reported as their orthogonal

mean diameters. Particle counts were performed by counting 1000 consecutive particles on five separate samples (n = 5000). Chemicalidentification ofthe particleswas attempted by both qualitative solubility tests and semiquantitative gas chromatography/mass spectrometric analysis. The solvents used for the solubility tests included 5N HCL, 5N NaOH, 20% sodium lauryl sulfate, 1,3-dichlorobenzene, 1,2-dichlorobenzene, chloroform, and 95% ethanol. Extracts in 1,3-dichlorobenzene of an authentic latex samplederived fromlatex gloves, a tire dust sample,and a PMao air sample were analyzed with a Hewlett Packard 5890/5882 gas chromatography/mass spectrometry system (Hewlett-Packard Co., Palo Alto, Calif.). Extraction of samples was performed with a heated (50°C) ultrasonic bath.Thechromatographicanalysiswasperformedwithan HP-1 capillary column operated in a temperature-controlled oven, programmed from 120° to 280°C at 10 degrees per minute. The mass spectrometrydetector was operated in electron impact mode and maintained at 250°C.The massrangerecordedwasfrommassto charge ratio = 30 to 500.



### Protein extraction and antigen studies
A rubber tire (Turanza-QL10, steel-belted radial; Bridgestone Tires, Warren County, Tenn.) with moderate wear was milled with a fine-tooth electric handsaw. Fragmentswerecollected onfilter paper (Whatman Qualitative;WhatmanPLC, Maidstone, Kent,England). A 100 gm sample was extracted for 30 seconds with 200 ml of distilledwaterinahigh-speedblender (Vitamix,Cleveland, Ohio). The preparation was filtered (Whatman Qualitative), dialyzed in cellulose dialysis tubing against distilled
water (Spectroporwith a nominal molecularweight cutoff of 1000 kd; Spectrum, Houston, Texas), concentrated fore'fold by evaporation at room temperature and lyophilized. The rubber glove extractwas prepared according to themethodofKurup et ald2with powderless latexmedical gloves (Aladan Co., Dothan, Ala.). Competitiveinhibition assays were performed in duplicate with the Pharmacia CAP system (Kabi Pharmacia, Uppsala, Sweden). Equal volumes of serum and either lyophilized tire extract dissolved in saline solution, latex rubber glove extract dissolved in saline solution, or saline solution alone were incubated overnight at 4°C. Fifty-microliter aliquots of these sampleswere assayed in duplicate with native latex 

### (Heveabrasiliensis)protein extractas the solid-phase allergen source (Pharmacia CAP system). Individual serum samples containing latex-specific IgE from patients with clinical histories of latex reactivity were used. Identical inhibitions were performedwith a serum sample containing 5.3 kUa/L

### Altemaria-specific IgE for specificity controls. Inhibitionwas calculated with the formula:

Percent inhibition

= 100 x (1 - [response sample/responsesaline])



### RESULTS
The particles observed in the ambient air samples were black, rarely spherical, and typically

coarse with ragged edges (Fig. 1). The airborne quantity ranged from 3800 to 6900 particles per cubic meter. Their size varied greatly, but over 90% were between 2.2 and 35.2 Ixm in mean orthogonal diameter with a mode of 6.6 p~m (Fig. 2). A birch pollen grain, which is consistently around 35 p~m (in Calberla's solution), was included in the photograph for reference.31 A high percentage (58.5%) of the particles were in the90 Williams et al. JALLERGY CLINIMMUNOL JANUARY1995

FIG. 1. Photomicrograph of ambient air sample collected on impact sampler. A birch pollen grain (35 txm in diameter) was included for reference. (x450.)

AIRBORNE TIRE DEBRIS SIZE DISTRIBUTION

AMBIENT VOLUMETRIC SAMPLER COLLECTION

Percentage ofTotal Particles (n=5000) 20%

10% 15%

5%

0%2.2 6.6 11 15.4 19.8 24.2 28.6 33

FIG. 2. Distribution of tire debris size from impact sampler (n = 5000). Particle sizes were determined with a calibrated reticule with light microscopy. (x450.)



### respirable range ofless than 10 ~m.33 

### There was a sharp drop in the number ofparticles below4 p~m. Attempts to tease this material apart under the microscope indicated that it was pliable and resilient, regaining its original shape after stretching. In chloroform and the dichlorobenzenes the fragments underwent swelling, as is characteristic of cross-linked hydrophobic polymers. The smaller particles, in the range of 2 txm, seemed more rounded in shape and resembled oil droplets. However, these did not dissolve in any of the solvents, indicating that they were not simple bydrocarbons. The fragments produced in the laboratory exhibited similar characteristics and behaved similarly in the solvent tests. The total ion chromatograms for each of the three samples analyzed with gas chromatography/

mass spectrometry are shown in Fig. 3. The broad peak located between 16.5 and 18.5 minutes' retention time in each of the chromatograms is characteristic of a polymeric substance and produced similar mass spectra in each of the three samples. The most abundant ions in the mass spectrawere at mass to charge ratio = 75, 149, and 265, which is consistent with spectra observed for latex and cross-linked rubber.34 The results of the inhibition experiments are presented in Table I. All but one of the sera containing latex-specific IgE were inhibited bythe rubber tire extract, with varying degrees of inhibition. For each serum sample, the inhibition was generally equivalent to that achieved with a latex glove extract (1 mg of protein per milliliter) but occasionally higher with the rubber tire fragment
extract. The specificity of this cross-reactivity was confirmed bydemonstrating no inhibition 

### ofAlternaria-specific IgE by the rubber tire extract.
DISCUSSION

This study supports the hypothesis that latex allergens arepresent inparticulate airpollutants inJ ALLERGYCLINIMMUNOL Williams et al. 91

VOLUME95, NUMBER 1, PART 1



### 8000 Latexrubber glovesample

6o00

e~ < 4000 4

s 

### 2ooo~ i

~ tD 1~ 0 5 " 20

5000-

4000.:

3000

2000

1000

0 

### i Milled tire sample

10 15 20

5000

4000



### 3O0O

200O

1000 

### Iiil i Ambient air sample 

# lli!

lo 15 2-b

Retentiontime(minutes)

FIG. 3. Total ion chromatograms for each of the three samples extracted in dichlorobenzene. The broad peak observed in each of the samples at 16 to 18 minutes of retention time is indicative of a polymeric structure. The mass spectra obtained for the species in these peaks
were similar in each of the samples and were consistent with mass spectra observed for authentic latex samples.



### urban areas. The abundance of these black particles at a station 7.4 m above the surface ranged from 3800 to 6900 per cubic meter. The most prevalent size in our samples was 6 to 7 Ixm mean orthogonal diameter, and over 58.5% were of a sizethat is fullyrespirable.33Our hypothesis is that these particles represent abraded tire fragments, and it is supported bymass spectroscopic,physical, and chemical data. The mass spectroscopy indicated a similar spectrum for rubber tire fragments, latex gloves, and material collected from ambient air with a PMlo sampler. Physically, the particles

were resilient, regaining their original shape after they were teased apart; and the inability of a variety of solvents to dissolve these fragments suggests that they are composed of highly structured polymeric material. The use ofnatural latex as a constituent ofmost tires presents the possibility that tire fragments could be immunologically active. This possibility

was verified by demonstrating elutable latex antigen activity by the inhibition assays. Collectively, these data strongly indicate that respirable tire fragments, containing readily elutable latex antigens, are present in large quantities in urban air. Earlier studies on tire wear characterization failed to detect tire particles in the respirable rangeY37 In a series of studies in 1974, Pierson92 Williams et al. JALLERGY CLINIMMUNOL
JANUARY 1995

TABLE I. Inhibition of latex-specific IgE with glove and tire fragment extracts

Response to Response to % Inhibition Response % Inhibition Sample saline GE glove TE tire



### 1 4,378 177 95.96 277 93.67 2 4,762 815 82.88 594 87.53 3 4,853 1,028 78.81 640 86.81 4 6,665 1,345 79.82 1,742 73.86 5 10,180 6,725 33.94 4,899 51.87 6 11,848 10,071 14.99 7,955 32.86 7 14,414 12,058 16.34 14,311 0.71
GE, 

### Gloveextract;TE, 

### tireextract.

and Brachaczek3s concluded that although tire

wear was a significant pollutant (600,000 metric
tons per year in the United States), most of this

was in the form of nonsuspendable particles deposited adjacent to roadways. The majority of these data were derived from samples collected at ground level. They concluded that the average airborne amount (50,000 tons/yr) is equivalent to 20% of airborne particulate matter from gasoline engine exhaust, which is a substantial amount of airborne material. Consumption ofnatural rubber for tires and associated products worldwide has increased since this time and measures approximately 3.9 million metric tons yearly.39 In 1981,

an Environmental Protection Agency laboratory study characterized tire wear particulates with the

use ofa stainless steelwearing surface.4°This study failed to demonstrate rubber particles in the 1 to 10 ~m range but suggested that the lack of small particles may have resulted from their experimental design. It is possible that freshly worn rubber particles without additional abrasive material would form aggregates, excluding small particles

on cascade-type collectors. When cornstarch was added to their system as an abrasive, smaller particles were in fact observed. More recent studies indicate that tire dust of respirable size is a significant contribution to the carbonaceous aerosol of less than 3.5 txm in Los Angeles.41 Rubber tires are manufactured with varying concentrations of natural latex (cis 1,4-polyisoprene) and synthetic rubber (1,4-styrene polybutadiene).3° Truck tires have higher amounts of natural latex.4°The natural latex is desirable because it causes less friction and can withstand higher temperatures but has the propensity to release smaller particles on abrasive wear. Wear ofradial,

as opposed to bias ply, constructed tires also results in smaller particles,g°The increased prevalence of radial tire use over the past 2 decades could account for the smaller particle sizes seen in

our study. The factthat wewere ableto extract functionally intact latex antigens from abraded tire fragments

was somewhat surprising, considering the high temperatures ofvulcanization (130°C) and extensivecross-linking.5This extends other findings that latex allergens are thermally stable.8 The serum samples used for these experiments were from patients clinically sensitive to products containing natural latex. All contained high amounts of IgE specificto latex-derived antigens. Our experiments demonstrate essentially equivalent results at maximal inhibition with latex glove antigens and the rubber tire extract in all the serum samples tested. This indicates that a close relationship exists between the specificities of the antibodies being inhibited. Further studies are in progress to define the quantitative relationships on a protein basis. Chronic exposure to respirable fragments of rubber that contain carbon black, latex antigens, and sulfur wouldbe expected to have a number of health consequences. Respirable particles can act

as irritants, inducing nonspecific inflammation. Small particles suspended in polluted air have been significantly linked to hospital admissions for
treatment of asthma, particularly in young children.42 Furthermore, several studies have linked fineparticulate air pollution to increased mortality
rates in infants, aswell asin the general population in a number ofU.S. cities.23-25It has been demonstrated that respiratory irritants stimulate IgE responses to environmental allergens.43,44Thus the rubber particles by themselves or in conjunction with other particulates could contribute to allergic responses in respiratory tissues by acting as nonspecific adjuvants. Latexallergens mayalso act as specificadjuvants for IgE responses. Kurup et al. demonstrated high levels of IgE and blood eosinophilia in mice ex-J ALLERGYCLIN IMMUNOL Williams et ai. 93

VOLUME 95, NUMBER 1, PART 1


### posed to latex proteins by intranasal and intraperitoneal routes.45 

### The latex antigen exposed mice developed high levels of interleukins 4 and 5, consistent with the stimulation of CD4÷ T.e lymphocytes. Preferential stimulation of CD4+ T~etype lymphocytes results in enhanced production and secretion of IgE (interleukin-4 effect) and eosinophil differentiation (interleukin-5 effect).46 

### Thus latex allergens, by acting as an adjuvant for IgE responses, might contribute to allergic responses to unrelated allergens. Japanese studies have suggested an adjuvant effect of diesel fuel particulates.47 These authors demonstrated that enhanced IgE responses occur in animals exposed to diesel fuel exhaust particulates. Experiments with suspendedparticulate matter from urban districts of Japan have also been shown to have potent adjuvant effects on IgE responses.4sA dose of0.25 txggiven intranasally at 3-week intervals was sufficient to obtain an appreciable IgE effect. The air along busy roads had concentrations of 200 to 480 txg/m3of this material.48Although not addressed bythe authors, these samples of ambient polluted air were likely to contain rubber tire fragments, which could have contributed to the adjuvant effects observed. The interaction of airborne particulate matter with pollen grains has been studied, indicating a direct interaction between pollen surfaces and airborne particulates causing preactivation and altered antigenicity.49,5o Such effects were prominent in industrialized regions and near roads with heavy traffic.51 These interactions, coupled to the adjuvant effects predicted for rubber tire fragments, might explain the elevated incidence of pollinosis in urban areas, as seen in a study that compared the incidence of Japanese red cedar 

## (Cryptomeriajaponica) pollinosis in urban and rural areas,s2 Pollen counts were similar in both
areas, but an incidence of 13.2% among residents located near intercity roads was seen, whereas the incidence of cedar pollinosis among forest residents (exposedto little orno motorized traffic)was 5.1%. These results support the concept that pollinosis is augmented by air pollution and automobile by-products. An additional consequence ofexposure to latexcontaining airborne particles could be direct sensitization to latex antigens. The prevalence oflatex sensitization has been increasing at an alarming
rate. Recent reports indicate that up to 14% of health care workers and nearly 10% of atopic individuals are sensitized to latex; and the rate of sensitization in atopie individuals who are frequently exposed to latex has reached 36%.9 Although increased use of latex gloves and other products has been suggested, an additional risk factor may be breathing urban air polluted with respirable tire fragments containing latex antigens. These fragments could be acting both specifically and nonspecifically as an adjuvant for enhancing IgE responses. For example, a nonspecific irritant effect could enhance sensitization to inhaled antigens, which could include latex itself. A variety of inhaled particulates have been linked to adverse health effects including declining lung function, shortness of breath, wheezing, asthma attacks, chronic obstructivepulmonary disease, increased rates of hospitalization, and increased mortality rates.12-29These may be due to inert physical properties, direct toxic effects, carcinogens, or stimulation ofinflammatol~y reactions. We suggest that respirable rubber tire fragments,
not mentioned in these prior studies, may represent a potent stimulus for both specific and nonspecific inflammatory responses, which are not mutually exclusive possibilities. In light of the potential adjuvant and antigenic properties of these fragments, serious consideration must be given to the possible role of these particles in the initiation and perpetuation of respiratory tract diseases such as asthma, allergic rhinitis, and allergic conjunctivitis. The role ofthese particles in the sensitization to latex revealed by subsequent acute systemic reactions to latex exposure in a medical
context must also be considered. These observations permit the organization of systematic epidemiologic and immunologic studies to clarify the role of latex-bearing particulate air pollutants in pulmonary diseases and clinical latex allergy.

We thank Timothy Sullivan,MD, (Emory University School of Medicine) for his adviceand reviewof the manuscript; Don Steadman, PhD, (University of Denver); Robert Barkley,PhD, and Robert SieversPhD, (UniversityofColorado) fortheir assistance and advice. We also thank Kabi Pharmacia for providing reagent support; StevenArnold ofthe Colorado Department of Health for providingDenver ambient air filters; and Henry Van Engelen (Wolverine, Mich.)for his help in preparing the tire fragments.

REFERENCES

1. Greek BF, Rubber demand is expected to grow after 1991. Chem Engin News 1991;69:37-54. 2. Light DR, Dennis MS. Purification of a phenyltransferase that elongates cis-polyisoprene rubber from the latex of Hevea brasiliensis. J Biol Chem 1989;264:18589-97.94 Williams et al. J ALLERGYCLIN IMMUNOL JANUARY 1995

3. Semegen ST. Natural rubber. In: Morton M, ed. Rubber technology.NewYork: Von Nostrand Reinhold, 1973:152- 77. 4. Jaeger D, Kleinhans D, Czuppon AB, Xaver B. Latex specificproteins causing immediate-type cutaneous, nasal, bronchial, and systemic reactions. J ALLERGYCLIN1MMUROE 1992;89:759-68. 5. Czuppon AB, Chen Z, Rennert S, et al. The rubber elongation factor of rubber trees (Hevea brasiliensis) is the major allergenin latex. J ALLERGY CLINIMMUNOL1993;92:690-7. 6. IacobelliAM,McCuIloughJA, OwnbyDR. Theprevalence oflatex allergyin high risk medicalpersonnel [Abstract]. J ALLERGYCLINIMMUNOL1993;91:216. 7. Eghrari-Sabet JS, Slater JE. Latex allergy: a potentially serious respiratory disorder. J Respir Dis 1993;14:473-82. 8. Hamann CP. Natural rubber latex protein sensitivity in review.Am J Contact Dermatitis 1993;4:4-21. 9. Moneret-Vautrin D-A, Beaudouin E, Widmer S, et al. Prospective study of risk factors in natural rubber latex hypersensitivity. J ALLERGY CLINIMMUNOL1993;92:668-77. i0. Yassin MS, Sanyurah S, LieriMB, et al. Evaluation oflatex allergy in patients with meningomyelocele. Ann Allergy 1992;69:207-11. 11. Turjanmaa K. Incidence ofimmediate allergy to latex gloves in hospital personnel. Contact Dermatitis 1987;17:270-5. 12. Dockery DW, Pope CA, Xu X, et al. An association between air pollution and mortality in six U.S. Cities. N Engl J Med 1993;329:1753-9. 13. Pope CAIII, DockeryDW. Acute health effects ofPM-10 pollution on symptomatic and asymptomatic children. Am Rev Respir Dis 1992;145:1123-8. 14. Chestnut LG, Schwartz J, Savitz DA, Burchfiel CM. Pulmonary function and ambient particulate matter: epidemiological evidence from NHANES I. Arch Environ Health 1991;46:135-44. 15. XuXP, DockeryDW, WangLH. Effectsofairpollution on adult pulmonary function. Arch Environ Health 1991;46: 198-206. 16. Weiss KB, Wagener DK. Changing patterns of asthma mortality. JAMA 1990;294:1683-7. 17. National Center for Health Statistics. Economic costs of respiratory diseases. Washington DC, U.S. Government Printing Office, 1986. 18. Centers for Disease Control. Asthma-United States, 1980- 1987. MMWR 1990;39:493-7. 19. Gergen PJ, Mullally DI, Evans R. National survey of prevalence ofasthma among children in the United States, 1976-1980. Pediatrics 1988;81:1-7. 20. Williams MH. Increasing severity of asthma from 1960- 1987. N Engl J Med 1989;320:1015-6. 21. FlemingDM, Crombie DL. Prevalence of asthma and hay fever in England and Wales. Br Med J 1987;294:279-83. 22. Kagamimori S, Katoh T, Naruse Y, et al. The changing prevalence of respiratory symptoms in atopic children in response to air pollution. ClinAllergy 1986;16:299-308. 23. Rennick GJ,Jarman FC.Are childrenwith asthma affected by smog? Med J Aust 1992;156:837-41. 24. Braun-Fahrlander C, Ackermann-Liebrich U, Schwartz J, GnehmHP, Rutishauser M,Wanner HU.Airpollutionand respiratory symptoms in preschool children. Am Rev Respir Dis 1992;145:42-7. 25. Dockery DW, Ware JH, Ferris BG Jr, Speizer FE, Cook NR, Herman SM. Change in pulmonary function in children associated with air pollution episodes. J Air Pollut Control Assoc 1982;32:937-42. 26. Schwartz J. Particulate air pollution and daily mortality in Detroit. Environ Res 1991;56:204-13. 27. FairleyD. The relationship ofdailymortality to suspended particulates in Santa Clara County, 1980-1986. Environ Health Perspect 1990;89:159-68. 28. Schwartz J, Dockery DW. Particulate air pollution and daily mortality in Steubenville, Ohio. Am J Epidemiol 1992;135:12-9. 29. Pope CAIII, SchwartzJ, Ransom MR. Dailymortalityand PM-10 pollution in Utah Valley. Arch Environ Health 1992;47:211-7. 30. Stephens HL. The compounding and vulcanization ofrubber. In:Norton M, ed. Rubber technology.NewYork: Von Nostrand Reinhold, 1973:19-50. 31. SmithEG. Sampling and identifyingallergenicpollens and molds. San Antonio: Blewstone Press, 1984:22. 32. Kurup VP, KellyKJ, ResnickA, Bansal NK. Characterization of latex antigen and demonstration of latex-specific antibodies by enzyme-linked immunosorbent assay in patientswithlatexhypersensitivity. AllergyProc 1992;13:329- 34. 33. Martini R. Fundamentals of anatomy and physiology. 2nd ed. Englewood Cliffs,NewJersey: Prentice-Hall, 1992;758- 69. 34. Akhtar S, Micheal RS, Ooij WJ. Static SIMS of some aliphatic hydrocarbon polymers. Polym Mater Sci Eng 1988;59:1135-8. 35. Dannis ML Rubber dust from normal wear of tires. Rubber Chem Tech 1974;47:1011-37. 36. Cadle SH, Williams RE Gas and particle emissions from automobile tires in laboratory and field studies. GM Research Publication GMR-2542R, May 1978. 37. Evans JV, Hites RD. Emission ofpollutants from tirewear phase Ipreliminaryreport M71-166 EPAProject 6132, Oct 1971. Ann Arbor: Calspan Corporation, 1971. 38. Pierson WR, Brachaczek WW. Airborne particulate debris from rubber tires. Rubber Chem Technol 1974;47:1275-99. 39. Reisch MS. Rubber, slow growth ahead. Chem Engineer News 1993;71:24-33. 40. Bogdan L, Albrechinski TM. Characterization of tire wear particles. US Dept ofCommerce EPA PB82-153586, 1981. 41. Hildemann LM, Markowski GR, Cass GR. Chemicalcomposition of emissions from urban sources of fine organic aerosol. Environ SciTech 1991;25:744-59. 42. Tseng RY, Li CK, Spinks JA. Particulate air pollution and hospitalization for asthma. Ann Allergy 1993;68:425-32. 43. Zetterstrom O, Osterman K, Machado L, Johansson SG. Another smoking hazard: raised serum IgE concentration and increased risk of occupational allergy. Br Med J 198l;283:1215-7. 44. Takafuji S, Suzuki S, KoizumiK, et al. Enhancing effectof suspended particulate matter on the IgE antibody production in mice. Int Arch AllergyImmnnol 1989;90:1-7. 45. Kurup VP, Kumar A, Choi H, et al. Latex antigens induce IgE and eosinophils in mice. Int Arch Allergy Immunol 1994;103:370-7. 46. Mario R. T cells, cytokines, IgE and allergicinflammation. Int Arch AllergyAppl Immunol 1992;99:165-71. 47. Muranaka M, Suzuki S, KoizumiK, et al. Adjuvant activity of diesel exhause particulates for the production of IgE antibody in mice. J ALLERGYCLrNIMMUNOL1986;77:616- 23. 48. Takafuji S, Suzuki S, Ko/zumi K, et al. Diesel-exhaust particulates innoculated by the intranasal route have anJ ALLERGYCLIN IMMUNOL Williams et aL 95

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adjuvant activity for IgE production in mice. J ALLERGY CLINIMMUNOL1987;79:639-45. 49. Behrendt H, Becket WM, Friedrichs KH, Darsow U, Tomingas R. Interaction between aeroallergens and airborne particulate matter. Int Arch AllergyAppl Immunol 1992;99:425-8. 50. Wolters JHB, Matens MJM. Effects of air pollutants on pollen. Botany Rev 1987;53:372-414. 51. Kainka-Stanicke E, Behrendt H, Fredrichs KH, Tomingas R. Morphological alterations ofpollen and spores induced by airborne pollutants: observations from two differently polluted areas in West Germany. Allergy 1988;43:57. 52. Ishizaka T, Koizumi K, IlkemoriR, Ishiyama Y, Kushibiki E. Studies of prevalence of Japanese cedar pollinosis among residents in a densely cultivated area. Ann A!lerg7 1987;58:265-70.



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