Health assessment of future PM2.5 exposures from indoor, outdoor, and secondhand tobacco smoke concentrations under alternative policy pathways in Ulaanbaatar, Mongolia

INTRODUCTION

Winter air pollution in Ulaanbaatar, Mongolia is among the worst in the world. The health impacts of policy decisions affecting air pollution exposures in Ulaanbaatar were modeled and evaluated under business as usual and two more-strict alternative emissions pathways through 2024. Previous studies have relied on either outdoor or indoor concentrations to assesses the health risks of air pollution, but the burden is really a function of total exposure. This study combined projections of indoor and outdoor concentrations of PM2.5 with population time-activity estimates to develop trajectories of total age-specific PM2.5 exposure for the Ulaanbaatar population. Indoor PM2.5 contributions from secondhand tobacco smoke (SHS) were estimated in order to fill out total exposures, and changes in population and background disease were modeled. The health impacts were derived using integrated exposure-response curves from the Global Burden of Disease Study.

RESULTS

Annual average population-weighted PM2.5 exposures at baseline (2014) were estimated at 59 μg/m3. These were dominated by exposures occurring indoors, influenced considerably by infiltrated outdoor pollution. Under current control policies, exposures increased slightly to 60 μg/m3 by 2024; under moderate emissions reductions and under a switch to clean technologies, exposures were reduced from baseline levels by 45% and 80%, respectively. The moderate improvement pathway decreased per capita annual disability-adjusted life year (DALY) and death burdens by approximately 40%. A switch to clean fuels decreased per capita annual DALY and death burdens by about 85% by 2024 with the relative SHS contribution increasing substantially.

CONCLUSION

This study demonstrates a way to combine estimated changes in total exposure, background disease and population levels, and exposure-response functions to project the health impacts of alternative policy pathways. The resulting burden analysis highlights the need for aggressive action, including the elimination of residential coal burning and the reduction of current smoking rates.

Substrate specificity of isopenicillin N synthase

Highly purified isopenicillin N synthase (IPNS) from two sources (naturally occurring in Penicillium chrysogenum and that expressed in Escherichia coli via a cloned gene derived from Cephalosporium acremonium) have been isolated and utilized in vitro to test synthetic modifications of the natural substrate, (L-alpha-amino-delta-adipyl)-L-cysteinyl-D-valine (ACV). A very sensitive procedure utilizing the ability of beta-lactams to induce the synthesis of beta-lactamase was employed to determine whether an ACV analogue could serve as a substrate for IPNS. A wide variety of amino and carboxyl terminal tripeptide substitutions were examined and found to elicit positive beta-lactamase induction profiles. However, none of these modifications were found to function as efficiently as a substrate as ACV. One of the beta-lactam products which was formed from the reaction of IPNS and the tripeptide analogue was independently synthesized and evaluated for antibacterial activity. Modification of the L-cysteine residue in the second position of ACV resulted in tripeptides that were unable to serve as substrates. Conversion of the D-valine residue in the third position of ACV to an aromatic amino acid or to a highly electronegative residue such as trifluorovaline resulted in elimination of substrate activity and creation of an inhibitor of the enzyme.

Antibacterial properties of the bicyclic pyrazolidinones

LY173013 and LY186826 are bicyclic pyrazolidinones containing a novel aza-gamma-lactam ring structure. The antibacterial properties of these compounds appear to be related to those of beta-lactam antibiotics in that both classes of compounds share certain common binding molecules such as beta-lactamases and penicillin-binding proteins.

Pharmaceutical interventions for obesity: a public health perspective

The prevalence of obesity, a major risk factor for many chronic diseases, has risen in most developed countries over the past several decades. The economic burden for both public and private health care systems is substantial. Although certain non-pharmaceutical interventions have been proven efficacious in specific populations, the lack of scalability has caused many of these programmes to fail in sustainably decreasing the percent of patients who are overweight or obese. The benefits of other interventions, such as pharmaceutical agents, medical devices and surgery, should therefore be carefully considered: this article focuses on the first of these strategies. Various pharmaceutical products have been plagued with safety concerns or patient non-adherence because of unpleasant side effects. Therefore, the need for additional antiobesity drugs that are both safe and effective is considerable. This article discusses the regulatory landscape for the development of new antiobesity compounds in the United States and Europe and considers the ramifications of greater or lesser regulatory burdens.

Stress-induced changes in the rate of sodium excretion in healthy black and white men

The effects of exposure to competitive mental stressors on rates of excretion of sodium (Na), potassium (K) and fluid, together with cardiovascular responses, were evaluated in 14 black and 14 white normotensive men after 3 days of controlled diet (200 mEq Na, 100 mEq K daily). In the first hour of a 5-hr protocol, subjects ingested a standard dinner and drank 1 liter of water. In hours 2-5, they voided to provide urine collections every 30 min, and drank 200 ml additional water after each collection. Hours 1-2 were for stabilization of excretion, hour 3 was baseline, hour 4 was stress and hour 5 was post-stress rest. During stress, 20 men showed faster natriuresis and 8 showed slower natriuresis than at baseline. These subgroups did not differ in any excretion measure at baseline. During stress, the slow stress natriuresis group showed slower excretion of potassium and fluid as well as sodium; slow natriuresis and kaliuresis persisted 30 min after stress. Creatinine clearance rate was also decreased, but only during the first 30 min of stress. Slow stress natriuresis subjects were found to have higher blood pressures during baseline and stress, greater heart rate and cardiac output increases during stress, and a larger percentage had hypertensive parents (63 vs 37%) compared to fast stress natriuresis subjects. Slow stress natriuresis was observed in 50 vs 17% of men with resting diastolic levels above vs below 80 mmHg, and in 43% of blacks vs 18% of whites tested. Overall, black subjects tended to excrete sodium more slowly than whites at baseline, and showed significantly lesser increases in sodium excretion rate when pressures rose during stress.

Reactivity to stress and psychological adjustment in adults with pituitary insufficiency

OBJECTIVE

Hypopituitary adults who were affected during childhood have a below-average rate of marriage, a rate of unemployment that exceeds national norms, and often indicate dissatisfaction with their life circumstances. We undertook the present study to determine the effects of short stature versus those of pituitary hormone deficiency.

DESIGN AND PATIENTS

We compared hypopituitary adults (n = 25) with normal short adults (n = 25) who were matched for height, sex, age and socioeconomic status.

MEASUREMENTS

In these two groups of subjects, we compared the physiological responses to a simulated social stressor, a public speaking task, and we measured the psychometric attributes that are indicators of social assertiveness and extraversion.

RESULTS

Before, during and after the stress of public speaking, patients with multiple pituitary hormone deficiencies (n = 20) had lower mean systolic and diastolic blood pressures than controls, while patients with isolated growth hormone deficiency (n = 5) were equivalent to controls. The reactivity to stress, assessed using delta scores based on changes in blood pressure and heart rate, was also decreased in multiple hormone deficient patients. Psychometric test results indicated that patients with multiple hormone deficiencies showed lower openness, lower assertiveness, greater neuroticism and a tendency towards less extraversion than did controls. The responses of patients with isolated GH deficiency on the psychometric tests were not statistically different from controls, but the number of subjects in this group (n = 5) was too small to draw conclusions.

CONCLUSIONS

The impaired cardiovascular responses to stress in patients with multiple hormone deficiencies, compared to short control subjects and to patients with GH deficiency leads us to conclude that factors other than stature and GH are responsible for these observations. The differences might be related to insufficiency of catecholamines or cortisol in the patients with multiple hormone deficiencies. These hormonal deficiencies might also account for the socially inhibited behaviour of these patients. Our results suggest that more attention needs to be directed at preparing hypopituitary patients for the challenges of adulthood. Also, these patients may be helped by more intensive efforts at hormonal replacement in adulthood.

Fine Particulate Matter and Parkinson Disease Risk Among Medicare Beneficiaries

BACKGROUND AND OBJECTIVES

Numerous studies suggest that environmental exposures play a critical role in Parkinson disease (PD) pathogenesis, and large, population-based studies have the potential to advance substantially the identification of novel PD risk factors. We sought to study the nationwide geographic relationship between PD and air pollution, specifically PM2.5 (particulate matter with a diameter <2.5 micrometers), using population-based US Medicare data.

METHODS

We conducted a population-based geographic study of Medicare beneficiaries aged 66-90 years geocoded to US counties and zip+4. We used integrated nested Laplace approximation to create age, sex, race, smoking, and health care utilization-adjusted relative risk (RR) at the county level for geographic analyses with PM2.5 as the primary exposure of interest. We also performed an individual-level analysis using logistic regression with cases and controls with zip+4 centroid PM2.5. We adjusted a priori for the same covariates and verified no confounding by indicators of socioeconomic status or neurologist density.

RESULTS

Among 21,639,190 Medicare beneficiaries, 89,390 had incident PD in 2009. There was a nationwide association between average annual PM2.5 and PD risk whereby the RR of PD was 56% (95% CI 47%-66%) greater for those exposed to the median level of PM2.5 compared with those with the lowest level of PM2.5. This association was linear up to 13 μg/m3 corresponding to a 4.2% (95% CI 3.7%-4.8%) greater risk of PD for each additional μg/m3 of PM2.5 (p trend < 0.0001). We identified a region with high PD risk in the Mississippi-Ohio River Valley, where the risk of PD was 19% greater compared with the rest of the nation. The strongest association between PM2.5 and PD was found in a region with low PD risk in the Rocky Mountains. PM2.5 was also associated with PD in the Mississippi-Ohio River Valley where the association was relatively weaker, due to a possible ceiling effect at average annual PM2.5 levels of ∼13 μg/m3.

DISCUSSION

State-of-the-art geographic analytic techniques revealed an association between PM2.5 and PD that varied in strength by region. A deeper investigation into the specific subfractions of PM2.5 may provide additional insight into regional variability in the PM2.5-PD association.

Severity of parkinsonism associated with environmental manganese exposure

BACKGROUND

Exposure to occupational manganese (Mn) is associated with neurotoxic brain injury, manifesting primarily as parkinsonism. The association between environmental Mn exposure and parkinsonism is unclear. To characterize the association between environmental Mn exposure and parkinsonism, we performed population-based sampling of residents older than 40 in Meyerton, South Africa (N = 621) in residential settlements adjacent to a large Mn smelter and in a comparable non-exposed settlement in Ethembalethu, South Africa (N = 95) in 2016-2020.

METHODS

A movement disorders specialist examined all participants using the Unified Parkinson Disease Rating Scale motor subsection part 3 (UPDRS3). Participants also completed an accelerometry-based kinematic test and a grooved pegboard test. We compared performance on the UPDRS3, grooved pegboard, and the accelerometry-based kinematic test between the settlements using linear regression, adjusting for covariates. We also measured airborne PM_2.5-Mn in the study settlements.

RESULTS

Mean PM_2.5-Mn concentration at a long-term fixed site in Meyerton was 203 ng/m³ in 2016-2017 - approximately double that measured at two other neighborhoods in Meyerton. The mean Mn concentration in Ethembalethu was ~ 20 times lower than that of the long-term Meyerton site. UPDRS3 scores were 6.6 (CI 5.2, 7.9) points higher in Meyerton than Ethembalethu residents. Mean angular velocity for finger-tapping on the accelerometry-based kinematic test was slower in Meyerton than Ethembalethu residents [dominant hand 74.9 (CI 48.7, 101.2) and non-dominant hand 82.6 (CI 55.2, 110.1) degrees/second slower]. Similarly, Meyerton residents took longer to complete the grooved pegboard, especially for the non-dominant hand (6.9, CI -2.6, 16.3 s longer).

CONCLUSIONS

Environmental airborne Mn exposures at levels substantially lower than current occupational exposure thresholds in the United States may be associated with clinical parkinsonism.

Comparison of cardiac versus vascular reactors and ethnic groups in plasma epinephrine and norepinephrine responses to stress

This study examined differences in plasma epinephrine (EPI) and norepinephrine (NOREPI) responses to stressors in 67 healthy African-American and Caucasian American men and women of the ages 18 to 49. Subjects were divided into three groups: (a) those who showed high blood pressure (BPI responses to stress associated with consistently high cardiac output (CO) increases with no substantial increases in total peripheral resistance (TPR), labeled cardiac reactors: (b) those with equally high BP increases associated with consistently higher TPR increases and lesser CO increases. labeled vascular reactors; (c) those who showed mixed hemodynamic responses or were low BP reactors. Ethnic and gender group differences in EPI and NOREPI responses were also examined. Cardiac reactors, vascular reactors and mixed + low reactors did not differ in EPI or NOREPI levels at baseline. During stressors, cardiac reactors showed greater increases in plasma EPI than vascular reactors or others during math, reaction time, and passive and active speech tasks: they also showed a weak trend toward greater NOREPI increases during these challenges as well. No differences were seen during the cold pressor: this stressor evoked the least change in EPI of all tasks, whereas the active speech elicited the greatest increases in both EPI and NOREPI of all tasks. Vascular reactors did not differ from mixed + low reactors in EPI or NOREPI reactivity, and men and women did not differ in EPI or NOREPI reactivity to any task. In contrast, Black subjects showed greater increases in NOREPI levels across all stressors compared to White subjects. These findings have implications for investigations of the role of sympathetic nervous system activity in the pathogenesis of hypertension in both African-American and Caucasian American populations.

Race and gender comparisons: II. Predictions of work blood pressure from laboratory baseline and cardiovascular reactivity measures

In 148 Black and White men and women, laboratory measures of blood pressure (BP), heart rate, stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) during baseline and 5 stressors were examined in relationship to ambulatory systolic (SBP) and diastolic (DBP) blood pressures at work. Baseline BP strongly predicted mean work levels in all groups. For White men and Black women, higher SV and CO responses to the active speech and averaged across all tasks predicted higher work SBP individually and also when added to a model based on baseline SBP, age, and diary information. For White women, higher SBP increases to the passive speech similarly predicted mean work SBP. For Black men, higher TPR response to the cold pressor test correlated with higher work SBP but did not improve a predictor model involving baseline SBP and age. Reactivity measures did not consistently contribute to prediction of work DBP.

Induction of kynureninase in Neurospora

Induction of kynureninase in a homogeneous population of mycelia in balanced growth was studied. Induced synthesis of enzyme was apparent 10 min after addition of inducers (tryptophan, kynurenine, and N-formylkynurenine). Experiments with cycloheximide-inhibited cells indicated that initiation of message transcription occurred about 4 min after addition of inducers. Lifetime of the message in the absence of inducer was of the order of 5 min. Experiments with mutants showed that N-formylkynurenine was the probable inducer of physiological importance.

Intertask consistency of hemodynamic responses to laboratory stressors in a biracial sample of men and women

Cardiovascular responses were examined in a community sample of 128 subjects, comprised of 58 African American and 70 Caucasian American men and women. Subjects completed a battery of laboratory stressors including mental arithmetic, reaction time, a speech task, and the cold pressor test. In addition to systolic and diastolic blood pressures, the underlying hemodynamic parameters of cardiac output and total peripheral resistance were assessed. In order to explore intertask consistency of response in both ethnic groups and both gender groups, correlational analyses were conducted separately for each group. For the psychological tasks, unanimously significant coefficients were observed. Intertask consistency between psychological tasks and the cold pressor was also considerable, but was somewhat less impressive (particularly for blood pressure) than that observed among the psychological tasks themselves. With regard to hemodynamic responses, cardiac output and total peripheral resistance demonstrated intertask consistency equal to, if not greater than, that shown by systolic and diastolic blood pressure, this consistency being evident for each ethnic and each gender group.

Race and gender comparisons: I. Hemodynamic responses to a series of stressors

A sample of 155 adults, age 18-49 years, including nearly equal subgroups of Black and White men and women, underwent evaluation of cardiovascular reactivity during 5 behavioral stressors. Among the men, overall blood pressure increases to tasks did not differ, but Blacks showed generally higher total peripheral resistance, whereas Whites showed greater heart rate and cardiac output increases. Among the women, the same racial-group differences were evident during certain tasks, but not during others. Men showed greater overall systolic blood pressure increases than did women, and they also showed less recovery toward baseline levels in systolic and diastolic pressure and stroke volume 5 min after the stressors. Other gender differences were task specific. The possible contributions of structural changes in the myocardium and vasculature, of altered sympathetic receptor distribution, and of task-specific behavioral factors influencing task involvement are discussed.

Lack of correlation between beta-lactamase production and susceptibility to cefamandole or cefoxitin among spontaneous mutants of Enterobacteriaceae

A large number of cultures of gram-negative bacteria were examined for their susceptibility to various concentrations of cefamandole, cefoxitin, carbenicillin, and nalidixic acid. Heterogeneity of susceptibility was demonstrated in individual cultures to all of these antibiotics. Resistant clones isolated from cefamandole or cefoxitin plates were examined for beta-lactamase production. Approximately 13% of 262 resistant clones acquired the ability to produce a beta-lactamase. Examination of the substrate profile of the beta-lactamases from some of these clones revealed no change in the specific activity of these enzymes for cefamandole, cephaloridine, or compound 87/312 as compared with their parental enzymes. This study clearly shows that some resistant clones do not produce beta-lactamases, whereas some susceptible strains produced significant amounts of these enzymes. We conclude from these findings that little correlation exists between beta-lactamase production and decreased susceptibility to cefamandole or cefoxitin. The results suggest the possibility that characteristics other than beta-lactamase production may be responsible for resistance in Enterobacteriaceae.

Colonization of the intestinal tract of conventional mice with Candida albicans and treatment with antifungal agents

Conventional mice inoculated with Candida albicans per os were unable to maintain this organism in the intestinal tract as judged by decreasing numbers of yeast recoverable from feces. After inoculation with 10(7) cells/mouse, fecal counts ranged from 10(5) cells per g of feces to 5 x 10(3) cells per g of feces during a 12-day experimental period. Addition of various antibiotics to the drinking water did not result in any improvement in maintenance or stability of the gut population. A combination of X irradiation and administration of tobramycin or gentamicin, however, resulted in a stable population of C. albicans in the intestinal tract, with cell counts in the feces remaining constant at a level of about 10(6)/g of feces for a period of 10 to 15 days. The usefulness of this model in assessing the effect of experimental drugs on C. albicans infections of the gut was demonstrated by the fact that treatment with a new antifungal antibiotic (A9145), amphotericin B, 5-fluorocytosine, or nystatin resulted in a reduction in the fecal counts of C. albicans from experimentally infected animals.

Depression and anxiety in a manganese-exposed community

OBJECTIVE

To characterize the association between residential environmental manganese (Mn) exposure and depression and anxiety, given prior associations among occupationally-exposed workers.

METHODS

We administered the Beck Depression Inventory (BDI) and the State-Trait Anxiety Inventory (STAI) to 697 study participants in their preferred languages. These participants represented a population-based sample of residents aged ≥40 from two predominantly Black African communities in Gauteng province, South Africa: 605 in Meyerton, adjacent to a large Mn smelter, and 92 in Ethembalethu, a comparable non-exposed community. We investigated the associations between community (Meyerton vs. Ethembalethu) and severity of depression and anxiety, using linear regression, adjusting for age and sex. To document community-level differences in Mn exposure, we measured airborne PM_2.5-Mn.

RESULTS

Meyerton residents had BDI scores 5.63 points (95 % CI 3.07, 8.20) higher than Ethembalethu residents, with all questions contributing to this significant difference. STAI-state scores were marginally higher in Meyerton than Ethembalethu residents [2.12 (95 % CI -0.17, 4.41)], whereas STAI-trait scores were more similar between the communities [1.26 (95 % CI -0.82, 3.35)]. Mean PM_2.5-Mn concentration was 203 ng/m³ at a long-term fixed site in Meyerton and 10 ng/m³ in Ethembalethu.

CONCLUSION

Residence near Mn emission sources may be associated with greater depression symptomatology, and possibly current, but not lifetime, anxiety.

Generalization of cardiovascular response: supportive evidence for the reactivity hypothesis

Cardiovascular responses were monitored while 36 subjects completed a battery of laboratory stressors comprising mental arithmetic, a reaction time task, a speech task, and the forehead cold pressor. Inter-task consistency was assessed for each of 6 physiological parameters for all task pairings. Considerable inter-task consistency for reactivity scores was seen among the psychological stressors for all variables. The question of such consistency between the cold pressor and the psychological tasks was then addressed. The pattern of consistency was not as clear-cut in this case. For systolic blood pressure and pre-ejection period, reactivity scores to the cold pressor did not correlate with those to any of the psychological tasks. In contrast, cardiac output and total peripheral resistance responses showed considerable consistency. The importance of determining the nature of the relationship between psychological and physical stressors is discussed.

Branched-chain fatty acids produced by mutants of Streptomyces fradiae, putative precursors of the lactone ring of tylosin

Three branched-chain fatty acids (7-hydroxy-4,6-dimethylnona-2,4-dienoic acid [compound 1], its 7-epimer [compound 2], and 7-keto-4,6-dimethylnona-2,4-dienoic acid [compound 3]) and a ketone (9-hydroxy-6,8-dimethylundeca-4,6-dien-3-one [compound 4]) were isolated from the culture broth of mutants of Streptomyces fradiae which were blocked in the biosynthesis of the macrolide antibiotic tylosin. Two phenotypic classes of mutants of this organism which were blocked in the addition of mycaminose to tylactone (compound 6) accumulated these compounds. These compounds were not produced by mutants which were blocked in lactone synthesis, in steps beyond mycaminose addition, or by the wild-type strain. Synthesis of these compounds, like synthesis of tylosin, was inhibited by the addition of cerulenin. Compounds 1, 2, and 3 were partially interconvertible by these mutants; but they were not produced from the degradation of tylactone and they were not directly incorporated into tylosin by intact cells. The structures of compounds 1 and 2 were equivalent to that of a predicted intermediate (S. Yue, J. S. Duncan, Y. Yamamoto, and C. R. Hutchinson, J. Am. Chem. Soc. 109:1253-1255, 1987) in the biosynthesis of tylactone. The ketone (compound 4) reported previously (N. D. Jones, M. O. Chaney, H. A. Kirst, G. M. Wild, R. H. Baltz, R. L. Hamill, and J. W. Paschal, J. Antibiot. 35:420-425, 1982) appears to be the decarboxylation product of the intermediate following that represented by compound 1. This represents the first report of the isolation of putative precursors of tylactone from tylosin-producing organisms.

Familial and individual influences on blood pressure

Although familial aggregation of blood pressure is well documented, few studies have considered the changing contribution of genetic and environmental influences during adulthood. Applying maximum likelihood model fitting to blood pressure covariation in balanced pedigrees including both parents and their young adult twin offsprings (25 MZ, 32 DZ, aged between 16 and 24 years), it is shown that the increased variation in parents is explained by such developmental changes. For DBP, an apparent reduction in heritability from 68% to 38% from young adulthood to middle age results from the increasing impact of individual environmental experience (E1), with little or no influence from shared family environmental (E2). For SBP, shared environmental effects may play a part. Given the relatively small size of the present sample, the conclusions are to be seen as tentative. An augmented family study, incorporating middle aged twins and their young adult offspring, will clarify the causation of these developmental changes.

Development of a wet-chemical method for the speciation of iron in atmospheric aerosols

The ability to quantify the chemical and physical forms of transition metals in atmospheric particulate matter (PM) is essential in determining potential human health and ecological effects. A method for the speciation of iron in atmospheric PM has been adapted which involves extraction in a well-defined solution followed by oxidation state specific detection. The method was applied to a suite of environmental aerosols. Ambient atmospheric aerosols in an urban area of St. Louis (the St. Louis-Midwest Supersite) were collected on Teflon substrates and were leached in one of four different solutions: (1) >18.0 Momega water; (2) 140 microM NaCl solution; (3) pH = 7.4 NaHCO3 solution; and (4) pH = 4.3 acetate buffering system. Fe(ll) was determined directly using the Ferrozine method as adapted to liquid waveguide spectrophotometry using a 1 m path-length cell. Fe(lll) was determined similarly after reduction to Fe(ll). It was found that, at low ionic strength, pH exerted a major influence on Fe(ll) solubility with the greatest Fe(ll) concentration consistently found in the pH = 4.3 acetate buffer. Soluble Fe(lll) (as defined by a 0.2 microm filter) varied little with extractant, which implies that most of the Fe(lll) detected was colloidal. To characterize well-defined materials for future reference, NIST standard reference materials were also analyzed for soluble Fe(ll) and Fe(lll). For all SRMs tested, a maximum of 2.4% of the total iron (Urban Dust 1649a) was soluble in pH = 4.3 acetate buffer. For calibration curves covering the ranges of 0.5-20 microg/L Fe(ll), excellent linearity was observed in all leaching solutions with R2 values of > 0.999. Co-located filters were used to test the effect of storage time on iron oxidation state in the ambient particles as a function of time. On two samples, an average Fe(ll) decay rate of 0.89 and 0.57 ng Fe(ll) g(-1) PM day(-1) was determined from the slope of the regression, however this decrease was determined not to be significant over 3 months (95% confidence). As an application of this method to mobile source emissions, size-resolved PM10 samples were collected at the inlet and outlet of the Caldecott Motor Vehicle Tunnel in northern California. These samples indicate that the coarse fraction (PM10-PM2.5) contains almost 50% of the total soluble Fe(ll) in the aerosol.