Air exchange rates and advection-diffusion of CO2 and aerosols in a route bus for evaluation of infection risk.

As COVID-19 continues to spread, infection risk on public transport is concerning. Air exchange rates (ACH) and advection-diffusion of CO2 and particles were determined in a route bus to evaluate the infection risk. ACH increased with bus speed whether windows were open or closed, and ACH were greater when more windows were open. With two open windows, ACH was greater when a front and rear window were open than when two rear windows were open. With both front and rear ventilation fans set to exhaust, ACH was more than double that when both were set to supply. With air conditioning (AC) off, CO2 and particles spread proportionally at the same rate from a source, whereas with the AC on, the spread rate of particles was about half that of CO2 , because particles might be trapped by a prefilter on the AC unit. Infection risk can be reduced by equipping AC unit with an appropriate filter. Calculations with a modified Wells-Riley equation showed that average infection risk was reduced by 92% in the moving bus with windows open comparing to with windows closed. When the bus was moving with windows closed, exhaust fan operation reduced the average risk by 35%.

Simultaneous determination of the size and concentration of fine bubbles in water by laser-light scattering.

The preparation of nanoscale fine bubbles in water is an innovative technology, but no precise method for simultaneously measuring the size and concentration of such bubbles had previously been developed. We have developed a method for simultaneously determining the size and concentration of fine bubbles in water by a light-scattering technique. Dynamic light scattering gives the diffusion constant and particle size of fine bubbles, whereas static light scattering provides their concentration or molar mass. Static light scattering also provides the radius of gyration of the bubbles, thereby providing a means for validating measurements of the sizes of the fine bubbles.

Optimization of Flow Imaging Microscopy Setting Using Spherical Beads with Optical Properties Similar to Those of Biopharmaceuticals.

Flow imaging microscopy (FIM) is widely used to characterize biopharmaceutical subvisible particles (SVPs). The segmentation threshold, which defines the boundary between the particle and the background based on pixel intensity, should be properly set for accurate SVP quantification. However, segmentation thresholds are often subjectively and empirically set, potentially leading to variations in measurements across instruments and operators. In the present study, we developed an objective method to optimize the FIM segmentation threshold using poly(methyl methacrylate) (PMMA) beads with a refractive index similar to that of biomolecules. Among several candidate particles that were evaluated, 2.5-µm PMMA beads were the most reliable in size and number, suggesting that the PMMA bead size analyzed by FIM could objectively be used to determine the segmentation threshold for SVP measurements. The PMMA bead concentrations measured by FIM were highly consistent with the indicative concentrations, whereas the PMMA bead size analyzed by FIM decreased with increasing segmentation threshold. The optimal segmentation threshold where the analyzed size was closest to the indicative size differed between an instrument with a black-and-white camera and that with a color camera. Inter-instrument differences in SVP concentrations in acid-stressed recombinant adeno-associated virus (AAV) and protein aggregates were successfully minimized by setting an optimized segmentation threshold specific to the instrument. These results reveal that PMMA beads can aid in determining a more appropriate segmentation threshold to evaluate biopharmaceutical SVPs using FIM.

Oral administration of Bis(aspirinato)zinc(II) complex ameliorates hyperglycemia and metabolic syndrome-like disorders in spontaneously diabetic KK-A(y) mice: structure-activity relationship on zinc-salicylate complexes.

In recent years, the number of patients suffering from diseases, such as cancer, apoplexy, osteoporosis, hypertension, and type 2 diabetes mellitus is increasing worldwide. Type 2 diabetes, a lifestyle-related disease, is recognized as a serious disease. Various types of pharmaceutics for diabetes have been used. Since the relationship between diabetes and biometals such as vanadium, copper, and zinc ions has been recognized for many years, we have been developing the anti-diabetic metal complexes as new candidates. We found that several zinc(II) (Zn) complexes exhibit glucose-lowering activity for treating type 2 diabetes. High doses of salicylates have been known to reverse hyperglycemia and hyperinsulinemia in type 2 diabetic patients. These findings strongly suggest that the combined use of Zn and salicylates achieves the synergism in treating type 2 diabetes. Because aspirin, acetyl salicylic acid, has a chelating ability, we used it as a ligand to Zn. Several Zn-salicylate complexes were prepared and their biological activities were examined in this study. The complexes with an electron-withdrawing group in the ligand exhibited higher in vitro insulinomimetic activity than those of Zn complexes with an electron-donating group in the ligand. When bis(aspirinato)Zn (Zn(asp)2) complex was orally administered on KK-A(y) mice with hereditary type 2 diabetes, the diabetic state was improved. In addition, this complex exhibited normalizing effects on serum adiponectin level and high blood pressure in metabolic syndrome. In conclusion, Zn(asp)2 complex is newly proposed as a potent anti-diabetic and anti-metabolic syndrome agent.

Determination of the Rayleigh Ratio with an Uncertainty Analysis by Static Light-Scattering Measurements of Certified Reference Materials for Molecular Weight.

The most important parameter for light-scattering measurements in the Rayleigh scattering region is the Rayleigh ratio, which is necessary to obtain the absolute scattered light intensity from the relative scattered light intensity. The absolute scattered light intensity is directly related to the molar masses of polymers, colloids, biomolecules, and the like. A new Rayleigh ratio was determined by measuring static light scattering from certified reference materials with highly accurate certified values of the molecular weight determined by several other techniques, such as MALDI-TOF mass spectrometry or size-exclusion chromatography. The new Rayleigh ratio can be used for evaluating the uncertainty of the molecular weight of polymers and macromolecules, as measured by light scattering.

Improvement of aging-associated cardiovascular dysfunction by the orally administered copper(II)-aspirinate complex.

BACKGROUND: Aging-associated nitro-oxidative stress causes tissue injury and activates proinflammatory pathways that play an important role in the pathogenesis of aging-associated cardiovascular dysfunction. It has been recently reported, that the copper(II)-aspirinate complex (CuAsp) exerts not only the well-known anti-inflammatory and platelet antiaggregating effects of aspirin, but, due to its superoxide dismutase mimetic activity, it acts as a potent antioxidant as well. In this study we investigated the effects of CuAsp on aging-associated myocardial and endothelial dysfunction. METHODS AND RESULTS: Aging and young rats were treated for 3 weeks with vehicle, or with CuAsp (200 mg/kg per day per os). Left ventricular pressure-volume relations were measured by using a microtip pressure-volume conductance catheter, and indexes of contractility (e.g., slope of end-systolic pressure-volume relationships [ESPVR] [E(es)], and dP/dt(max) - end-diastolic volume [EDV]) were calculated. In organ bath experiments for isometric tension with isolated aortic rings, endothelium-dependent and -independent vasorelaxation were investigated by using acetylcholine and sodium nitroprusside. When compared to the young controls, aging rats showed impaired left ventricular contractility (E(es), 0.51 +/- 0.04 vs. 2.16 +/- 0.28 mmHg/microL; dP/dt(max) - EDV, 10.71 +/- 2.02 vs. 37.23 +/- 4.18 mmHg/sec per microL; p < 0.05) and a marked endothelial dysfunction (maximal relaxation to acetylcholine: 66.66 +/- 1.30 vs. 87.09 +/- 1.35%; p < 0.05). Treatment with CuAsp resulted in reduced nitro-oxidative stress, improved cardiac function (E(es), 1.21 +/- 0.17 vs. 0.51 +/- 0.04 mmHg/microL; dP/dt(max) - EDV, 23.40 +/- 3.34 vs. 10.71 +/- 2.02 mmHg/sec per microL; p < 0.05) and higher vasorelaxation to acetylcholine in aging animals (94.83 +/- 0.73 vs. 66.66 +/- 1.30%; p < 0.05). The treatment did not influence the cardiovascular functions of young rats. CONCLUSIONS: Our results demonstrate that oxidative stress and inflammatory pathways contribute to the pathogenesis of cardiovascular dysfunction in the aging organism, which can be reversed by CuAsp.

Visualization and characterization of UVB-induced reactive oxygen species in a human skin equivalent model.

Reactive oxygen species (ROS) play important roles in the process of ultraviolet-induced skin damage or photoaging. Although many enzymatic and chemical methods have been developed for evaluating ROS, evaluation methods for ROS generation in living systems are quite limited. Here we propose a unique system to visualize UVB-induced ROS and investigate the biological impact of ROS. In brief, a human skin equivalent model (HSEM) was exposed to UVB. Emitted luminescence from the HSEM was visualized and semi-quantified by using a chemiluminescent probe (CLA) and an ultra low-light imaging apparatus. The effects of anti-oxidative compounds such as ascorbate, beta-carotene, superoxide dismutase (SOD), and yeast ferment filtrate (YFF) on the HSEM were evaluated by semi-quantification of emitted chemiluminescence (CL) intensities, MTT assay and 8-hydroxy-2'-deoxyguanosine (8-OHdG) staining. Visualization of time- and space-dependent dynamics of ROS generation in the HSEM was successfully achieved by utilizing a sensitive two-dimensional ultra-low light luminograph. Treatments with beta-carotene and SOD effectively suppressed CL intensity, indicating the generation of 1O2 and O2 .- in the HSEM under UVB exposure. Tested anti-oxidative compounds also attenuated UVB-induced CL and ameliorated the induced skin damages in terms of 8-OHdG formation and cell death. As a conclusion, this model is useful for not only visualizing the production of UVB-induced ROS in real-time but also evaluating the efficacy of topically applied anti-oxidative compounds to suppress ROS generation and attenuate sequential chemical and biological responses.

Antidiabetic activity of the orally effective vanadyl-poly (gamma-glutamic acid) complex in streptozotocin(STZ)-induced type 1 diabetic mice.

Newly synthesized vanadyl-poly(gamma-glutamic acid) complex (VO-gamma-PGA) with a VO(O4) coordination mode was found to have potent antidiabetic activity in streptozotocin (STZ)-induced type 1 diabetic mice (STZ-mice), compared with that of a solution containing only vanadyl sulfate, VOSO4. This was the first example of orally active vanadyl complex of gamma-PGA for treating STZ-mice. To better define its efficacy, we examined here the effects of VO-gamma-PGA treatment in STZ-mice by oral administration at the dose of 10 mg V/kg body mass for a longer period time than our previous study. The improvement in diabetic states in STZ-mice compared with saline-treated nondiabetic normal Std ddY mice. It was found that the elevated blood glucose levels in STZ-mice significantly decreased after 3 days and sustained the normalized blood glucose level around 180-200 mg/dL (10-11.1 mM) for the last 14 days, which is close to the blood glucose levels 100-200 mg/dL (5.6-11.1 mM) in nondiabetic normal Std ddY mice. The improvement in diabetes was strongly corelated by the improvement in oral glucose tolerance ability, glycosylated hemoglobin (HbA1c) levels and blood pressure, and serum parameters. The present results confirmed that VO-gamma-PGA complex is a promising, orally active insulin-mimetic agent to treat type 1 diabetic mice.

Action mechanism of insulin-mimetic vanadyl-allixin complex.

In the 21st century, there has been a dramatic worldwide increase in the prevalence of metabolic syndromes, including diabetes mellitus (DM). Several synthetic pharmaceutical agents have been developed and used for the treatment of type-2 DM; however, these compounds have several problems such as side effects, hypoglycemia, and weight gain. Therefore, new drugs are required for DM therapy. We have proposed that some vanadyl complexes function as potent insulin-mimetic and antidiabetic agents in type-1 and type-2 DM animal models. In this article, we review the possible action mechanism of insulin-mimetic and antidiabetic vanadyl complexes, focusing on a recently proposed complex, bis(allixinato)oxovanadium(IV), with respect to the insulin-signaling pathway in cultured adipocytes.

[Treatment of diabetes in experimental animals by metallocomplexes].

The number of patients suffered from diabetes mellitus has increased over the decades probably because of both lifestyle- and diet-changes. There are two types of diabetes mellitus. Type 1 diabetes mellitus is due to the autoimmune-mediated destruction of pancreatic B cells, which results in absolute insulin deficiency, thus the patients require insulin injections. Type 2 diabetes mellitus is due to the insulin resistance and abnormal insulin secretion, thus the patients require exercise, diet control and/or oral hypoglycemic medicines. Each treatment, however, has some problems involving physical and mental burden, and formation of self-antibodies for insulin injections, and the severe side effects and discontinuation of insulin synthesis in the pancreas for hypoglycemic medicines. To overcome these important problems and find the replacements for the insulin injections and synthetic medicines, we attempted to develop new antidiabetic metallocomplexes with novel structures and mechanisms. In 1990, we first presented orally active vanadyl (+4 oxidation state of oxo-vanadium) complexes including vanadyl-cysteine methyl ester complex, which normalized hyperglycemia in the streptozocin (STZ)-induced type 1 diabetic rats. Based on these findings, we have developed a wide variety of vanadyl complexes with different coordination environments around vanadyl ion. Following the study, we also challenged to develop orally active zinc complexes since 2002. This review focuses on our recent development of vanadyl and zinc complexes for anti-diabetic and anti-metabolic syndromes, together with the propose for the possible action mechanism of these complexes in adipocytes.

Overexpression of endothelial nitric oxide synthase accelerates atherosclerotic lesion formation in apoE-deficient mice.

Nitric oxide (NO) derived from endothelial NO synthase (eNOS) is regarded as a protective factor against atherosclerosis. Therefore, augmentation of eNOS expression or NO production by pharmacological intervention is postulated to inhibit atherosclerosis. We crossed eNOS-overexpressing (eNOS-Tg) mice with atherogenic apoE-deficient (apoE-KO) mice to determine whether eNOS overexpression in the endothelium could inhibit the development of atherosclerosis. After 8 weeks on a high-cholesterol diet, the atherosclerotic lesion areas in the aortic sinus were unexpectedly increased by more than twofold in apoE-KO/eNOS-Tg mice compared with apoE-KO mice. Also, aortic tree lesion areas were approximately 50% larger in apoE-KO/eNOS-Tg mice after 12 weeks on a high-cholesterol diet. Expression of eNOS and NO production in aortas from apoE-KO/eNOS-Tg mice were significantly higher than those in apoE-KO mice. However, eNOS dysfunction, demonstrated by lower NO production relative to eNOS expression and enhanced superoxide production in the endothelium, was observed in apoE-KO/eNOS-Tg mice. Supplementation with tetrahydrobiopterin, an NOS cofactor, reduced the atherosclerotic lesion size in apoE-KO/eNOS-Tg mice to the level comparable to apoE-KO mice, possibly through the improvement of eNOS dysfunction. These data demonstrate that chronic overexpression of eNOS does not inhibit, but accelerates, atherosclerosis under hypercholesterolemia and that eNOS dysfunction appears to play important roles in the progression of atherosclerosis in apoE-KO/eNOS-Tg mice.

Identification of free radical species derived from caffeic acid and related polyphenols.

Polyphenols are widely distributed in various fruits, vegetables and seasonings. It is well known that they have several physiological effects due to their antioxidative activities. Their activities depend on structural characteristics that favour the formation of their corresponding stable radicals. During the examination at which pH values, the polyphenol radicals are stabilized, we confirmed that polyphenol radicals were stabilized in NaHCO3/Na2CO3 buffer (pH 10) rather than in physiological pH region. Then, we measured electron spin resonance (ESR) spectra at pH 10 to examine the characteristics of free radical species derived from caffeic acid (CA) with an unsaturated side chain, dihydrocaffeic acid (DCA) with a saturated side chain, chlorogenic acid (ChA) and rosmarinic acid (RA). In analyzing the radical structures, ESR simulation, determinations of macroscopic and microscopic acid dissociation constants and molecular orbital (MO) calculation were performed. In CA, the monophenolate forms were assumed to participate in the formation of free radical species, while in DCA, the diphenol form and the monophenolate forms were presumed to contribute to the formation of free radical species. On the basis of the results, we propose the possible structures of the free radical species formed from polyphenols under alkaline conditions.

A new type of orally active anti-diabetic Zn(II)-dithiocarbamate complex.

In order to find orally active Zn(II) complexes that can treat diabetes mellitus (DM) at low doses, four new Zn(II)-dithiocarbamate complexes with Zn(II)-sulfur coordination bonds were prepared and their in vitro insulinomimetic activity and in vivo anti-diabetic ability were evaluated. Among the Zn(II)-dithiocarbamate complexes, the bis(pyrrolidine-N-dithiocarbamate)zinc(II) (Zn(pdc)(2)) complex was found to be the most effective in terms of inhibiting free fatty acid-release and enhancing glucose-uptake in adipocytes. After oral administration of the Zn(pdc)(2) complex to KK-A(y) mice with obesity and type 2 DM, we observed that the high blood glucose levels in the mice were lowered from approximately 500 mg/dL to 350 mg/dL within 6 days, and the effect was maintained during the administration period. Also, indicators of insulin resistance such as serum insulin, leptin, and triglyceride levels were also reduced compared with those in untreated mice. Moreover, the Zn(pdc)(2) complex improved not only the hypertension in the mice, but also the adiponectin level in the serum. On the basis of the results, the Zn(pdc)(2) complex is proposed to improve hyperglycemia and insulin resistance in type 2 DM animals on daily oral administrations.

Insulinomimetic Zn complex (Zn(opt)2) enhances insulin signaling pathway in 3T3-L1 adipocytes.

Zinc (Zn) is an essential trace element with multiple regulatory functions, involving insulin synthesis, secretion, signaling and glucose transport. Since 2000, we have proposed that Zn complexes with different coordination environments exhibit high insulinomimetic and antidiabetic activities in type 2 diabetic animals. However, the molecular mechanism for the activities is still unsolved. The purpose of this study was to reveal the molecular mechanism of several types of Zn complexes in 3T3-L1 adipocytes, with respect to insulin signaling pathway. Obtained results shows that bis(1-oxy-2-pyridine-thiolato)Zn(II), Zn(opt)2, with S(2)O(2) coordination environment induced most strongly Akt/protein kinase B (Akt/PKB) phosphorylation, in which the optimal phosphorylation was achieved at a concentration of 25 microM, and this Zn(opt)2-induced Akt/PKB phosphorylation was inhibited by wortmannin at 100 nM. Further, the phosphorylation was maximal at 5-10 min stimulation, in agreement with the Zn uptake which was also maximal at 5-10 min stimulation. The Akt/PKB phosphorylation was in concentration- and time-dependent manners. Zn(opt)2 was also capable to translocate GLUT4 protein to the plasma membrane. We conclude that Zn(opt)2 was revealed to exhibit both insulinomimetic and antidiabetic activities by activating insulin signaling cascade through Akt/PKB phosphorylation, which in turn caused the GLUT4 translocation from the cytosol to the plasma membrane.

Aluminum compounds enhance lipid peroxidation in liposomes: insight into cellular damage caused by oxidative stress.

Aluminum (Al) has been proposed as one of the critical environmental factors responsible for several neurodegenerative diseases such as Alzheimer's disease. However, the suggested mechanism involving the contribution of reactive oxygen species still remains controversial. We have first attempted to identify Al compounds either in its ionic or complexed forms that cause oxidative stress in biological systems. For this purpose, we examined the effect of inorganic Fe(2+)- and organic radical initiator (2,2'-azobis (2-amidinopopane) hydrochloride; AAPH)-induced lipid peroxidation by using aluminum (Al(3+)) nitrate and tris(maltolato)aluminum(III) complex (ALM) with respect to molecular oxygen (O(2)) consumption and membrane fluidity change in liposomes as biological membrane models. The following important results were obtained: (1) ALM enhanced the lipid peroxidation induced by Fe(2+) and AAPH in phosphatidylcholine liposomes; this corresponded well with the promotion of O(2) uptake in the same liposomes, (2) Al(3+) increased both lipid peroxidation and O(2) consumption in phosphatidylserine liposomes in the presence of Fe(2+), and (3) both Al(3+) and ALM affected the membrane fluidity on the inner side. It has been concluded that ALM induces higher lipid peroxidation in liposomes than Al(3+); this finding will be useful to gain an insight into the role of Al in cellular damage in relation to oxidative stress.

Investigation of a Cu(II)-poly(gamma-glutamic acid) complex in aqueous solution and its insulin-mimetic activity.

The complexation between cupric ions (Cu(II)) and poly(gamma-glutamic acid) (gamma-PGA) in aqueous solutions (pH 3-11) has been studied by UV-visible absorption and electron spin resonance (ESR) techniques. Formation of the Cu(II)-gamma-PGA complex is confirmed by the observation of the blue shift of the absorption band in the visible region, anisotropic line shapes in the ESR spectrum at room temperature, and a computer simulation of the visible absorption spectrum of the complex. The structure of the Cu(II)-gamma-PGA complex, depending on the pH, has been determined. The in vitro insulin-mimetic activity of the Cu(II)-gamma-PGA complex is examined by determining both inhibition of free fatty acid release and glucose uptake in isolated rat adipocytes treated with epinephrine, in which the concentration of the Cu(II)-gamma-PGA complex for 50% inhibition of free fatty acid release is very similar to that of CuSO4. However, it is significantly lower than that of a previously reported insulin-mimetic bis(3-hydroxypicolinato)copper(II), [Cu(3hpic)2], complex.

Improvement of hyperglycaemia and metabolic syndromes in type 2 diabetic KKAy mice by oral treatment with [meso-tetrakis(4-sulfonatophenyl) porphyrinato]oxovanadium(IV)(4-) complex.

Recently, we reported that [meso-tetrakis(4-sulfonatophenyl)porphyrinato]oxovanadium(IV)(4-), VO(tpps), shows in-vitro insulin-mimetic and in-vivo anti-diabetic activity in streptozotocin (STZ)-induced type 1 diabetic mice. This result prompted us to examine its ability in type 2 diabetic model KKA(y) mice with insulin resistance. We studied the in-vivo anti-diabetic activity of VO(tpps), compared with that of vanadium(IV) oxide sulfate, VS, as control. Both compounds were orally administered at doses of 5-10 mg (0.1-0.2 mmol) V/kg body weight to the KKA(y) mice for 28 days. VO(tpps) normalized the hyperglycaemia within 15 days, while VS lowered the blood glucose concentration only by a small degree. In addition, metabolic syndromes characterized by insulin and leptin resistance were significantly improved in VO(tpps)-treated KKA(y) mice compared with those treated with VS. The improvement in diabetes was validated by oral glucose tolerance test and decrease in HbA(1c) concentration. Based on these observations, VO(tpps) is proposed to be an orally active oxovanadium(IV)-porphyrin complex for treating not only type 2 diabetes but also metabolic syndromes in animals.

Relationship between trace metal concentration and antioxidative activity of ancient rice bran (red and black rice) and a present-day rice bran (Koshihikari).

Antioxidative activity and polyphenol and trace metal content in bran from ancient rice varieties (red and black rice) and a present-day variety of rice (Koshihikari) were measured. The antioxidative properties of rice bran in terms of scavenging and quenching activity for reactive oxygen species (ROS), including superoxide anion radicals (*O(2)(-)), hydroxyl radicals (*OH), singlet oxygen ((1)O(2)) and lipid peroxide (LOO*), correlated well with polyphenol and trace metal content. In particular, the possibly that Mn content greatly contributes to the antioxidative properties of rice bran was revealed.

Antidiabetic zinc(II)-N-acetyl-L-cysteine complex: evaluations of in vitro insulinomimetic and in vivo blood glucose-lowering activities.

The diabetic state is known to induce oxidative stress in its mechanism, which in turn is responsible for the complications of diabetes mellitus (DM). Recently, we found that Zn(II) complexes have in vitro insulinomimetic and in vivo blood glucose-lowering activities. During our study on the development of new Zn(II) complexes with antioxidative ligands involving L-cysteine, L-cysteine-methylester, and N-acetyl-L-cysteine (nac), we found a new (N-acetyl-L-cysteinato)Zn(II) (Zn(nac)) complex by evaluating of both its in vitro insulinomimetic and in vivo potencies. The insulinomimetic activity of Zn(nac) with respect to the inhibition of free fatty acid release in isolated rat adipocytes treated with epinephrine was higher than that of a well-known insulinomimetic VOSO4, being equivalent to that of ZnSO4. The blood glucose level of hyperglycemic KK-Ay mice with type 2 DM was reduced by daily intraperitoneal injections of Zn(nac) for 28 days. Their serum insulin, HbA1c, TCHO, and UN levels were remarkably decreased, indicating that Zn(nac) improved the insulin resistance of the mice. The improvement of DM by Zn(nac) was also confirmed by the oral glucose tolerance test. In conclusion, Zn(nac) complex is proposed to attenuate both hyperglycemia and hyperinsulinemia in KK-Ay mice by decreasing serum insulin, HbA1c, UN, and TCHO levels.

Use of the electrical aerosol detector as an indicator of the surface area of fine particles deposited in the lung.

Because of recent concerns about the health effects of ultrafine particles and the indication that particle toxicity is related to surface area, we have been examining techniques for measuring parameters related to the surface area of fine particles, especially in the 0.003- to 0.5-microm size range. In an earlier study, we suggested that the charge attached to particles, as measured by a prototype of the Electrical Aerosol Detector (EAD, TSI Inc., Model 3070), was related to the 1.16 power of the mobility diameter. An inspection of the pattern of particle deposition in the lung as a function of particle size suggested that the EAD measurement might be a useful indicator of the surface area of particles deposited in the lung. In this study, we calculate the particle surface area (micrometer squared) deposited in the lung per cubic centimeter of air inhaled as a function of particle size using atmospheric particle size distributions measured in Minneapolis, MN, and East St. Louis, IL. The correlations of powers of the mobility diameter, Dx, were highest for X = 1.1-1.6 for the deposited surface area and for X = 1.25 with the EAD signal. This overlap suggested a correspondence between the EAD signal and the deposited surface area. The correlation coefficients of the EAD signal and particle surface area deposited in the alveolar and tracheobronchial regions of the lung for three breathing patterns are in the range of Pearson's r = 0.91-0.95 (coefficient of determination, R2 = 0.82-0.90). These statistical relationships suggest that the EAD could serve as a useful indicator of particle surface area deposited in the lung in exposure and epidemiologic studies of the human health effects of atmospheric particles and as a measure of the potential surface area dose for the characterization of occupational environments.