Size-dependent influence of NOx on the growth rates of organic aerosol particles

Atmospheric new-particle formation (NPF) affects climate by contributing to a large fraction of the cloud condensation nuclei (CCN). Highly oxygenated organic molecules (HOMs) drive the early particle growth and therefore substantially influence the survival of newly formed particles to CCN. Nitrogen oxide (NOx) is known to suppress the NPF driven by HOMs, but the underlying mechanism remains largely unclear. Here, we examine the response of particle growth to the changes of HOM formation caused by NOx. We show that NOx suppresses particle growth in general, but the suppression is rather nonuniform and size dependent, which can be quantitatively explained by the shifted HOM volatility after adding NOx. By illustrating how NOx affects the early growth of new particles, a critical step of CCN formation, our results help provide a refined assessment of the potential climatic effects caused by the diverse changes of NOx level in forest regions around the globe.

Ion-induced sulfuric acid-ammonia nucleation drives particle formation in coastal Antarctica

Formation of new aerosol particles from trace gases is a major source of cloud condensation nuclei (CCN) in the global atmosphere, with potentially large effects on cloud optical properties and Earth's radiative balance. Controlled laboratory experiments have resolved, in detail, the different nucleation pathways likely responsible for atmospheric new particle formation, yet very little is known from field studies about the molecular steps and compounds involved in different regions of the atmosphere. The scarcity of primary particle sources makes secondary aerosol formation particularly important in the Antarctic atmosphere. Here, we report on the observation of ion-induced nucleation of sulfuric acid and ammonia-a process experimentally investigated by the CERN CLOUD experiment-as a major source of secondary aerosol particles over coastal Antarctica. We further show that measured high sulfuric acid concentrations, exceeding 10⁷ molecules cm^-3, are sufficient to explain the observed new particle growth rates. Our findings show that ion-induced nucleation is the dominant particle formation mechanism, implying that galactic cosmic radiation plays a key role in new particle formation in the pristine Antarctic atmosphere.

Effect of dimethylamine on the gas phase sulfuric acid concentration measured by Chemical Ionization Mass Spectrometry

Sulfuric acid is widely recognized as a very important substance driving atmospheric aerosol nucleation. Based on quantum chemical calculations it has been suggested that the quantitative detection of gas phase sulfuric acid (H₂SO₄) by use of Chemical Ionization Mass Spectrometry (CIMS) could be biased in the presence of gas phase amines such as dimethylamine (DMA). An experiment (CLOUD7 campaign) was set up at the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber to investigate the quantitative detection of H₂SO₄ in the presence of dimethylamine by CIMS at atmospherically relevant concentrations. For the first time in the CLOUD experiment, the monomer sulfuric acid concentration was measured by a CIMS and by two CI-APi-TOF (Chemical Ionization-Atmospheric Pressure interface-Time Of Flight) mass spectrometers. In addition, neutral sulfuric acid clusters were measured with the CI-APi-TOFs. The CLOUD7 measurements show that in the presence of dimethylamine (<5 to 70 pptv) the sulfuric acid monomer measured by the CIMS represents only a fraction of the total H₂SO₄, contained in the monomer and the clusters that is available for particle growth. Although it was found that the addition of dimethylamine dramatically changes the H₂SO₄ cluster distribution compared to binary (H₂SO₄-H₂O) conditions, the CIMS detection efficiency does not seem to depend substantially on whether an individual H₂SO₄ monomer is clustered with a DMA molecule. The experimental observations are supported by numerical simulations based on A Self-contained Atmospheric chemistry coDe coupled with a molecular process model (Sulfuric Acid Water NUCleation) operated in the kinetic limit.

A new atmospherically relevant oxidant of sulphur dioxide

Atmospheric oxidation is a key phenomenon that connects atmospheric chemistry with globally challenging environmental issues, such as climate change, stratospheric ozone loss, acidification of soils and water, and health effects of air quality. Ozone, the hydroxyl radical and the nitrate radical are generally considered to be the dominant oxidants that initiate the removal of trace gases, including pollutants, from the atmosphere. Here we present atmospheric observations from a boreal forest region in Finland, supported by laboratory experiments and theoretical considerations, that allow us to identify another compound, probably a stabilized Criegee intermediate (a carbonyl oxide with two free-radical sites) or its derivative, which has a significant capacity to oxidize sulphur dioxide and potentially other trace gases. This compound probably enhances the reactivity of the atmosphere, particularly with regard to the production of sulphuric acid, and consequently atmospheric aerosol formation. Our findings suggest that this new atmospherically relevant oxidation route is important relative to oxidation by the hydroxyl radical, at least at moderate concentrations of that radical. We also find that the oxidation chemistry of this compound seems to be tightly linked to the presence of alkenes of biogenic origin.

The pure-tone hearing thresholds of otologically healthy 14-year-old children

The mean pure-tone air conduction (AC) and bone conduction (BC) hearing thresholds (HT) of 534 randomly selected, caucasian, white, urban children with normal otoscopy, otomicroscopy and impedance audiometry, i.e. normal middle ear function, are presented here. Children with pathological middle ear findings or abnormal impedance audiometry were excluded. The average age was 13.8 years, SD 0.5, at the date of examination. The mean air conduction thresholds varied between 0.6 dB at 1 kHz and 9.9 dB at 6 kHz, and the bone conduction thresholds varied between -1.1 dB at 0.5 kHz and 1.1 dB at 4 kHz. The pure-tone average (PTA) (the average of AC hearing thresholds of 0.5, 1 and 2 kHz) of all ears was 1.5 dB. Ninety to ninety-eight per cent of pure-tone AC hearing thresholds at frequencies of 0.5-4 kHz were between -5 dB and 10 dB. The distributions are presented and compared.

Assignment of the disease locus for lethal congenital contracture syndrome to a restricted region of chromosome 9q34, by genome scan using five affected individuals

Lethal congenital contracture syndrome (LCCS) is an autosomal recessive disease leading to death before the 32d gestational week. It is characterized by the fetal akinesia phenotype, with highly focused degeneration of motoneurons in the spinal cord as the main neuropathological finding. We report here the assignment of the LCCS locus to a defined region of chromosome 9q34, between markers D9S1825 and D9S1830. The initial genome scan was performed with the DNA samples of only five affected individuals from two unrelated LCCS families. The conventional linkage analysis performed with 20 affected individuals and their families was focused on those chromosomal regions in which the affected siblings were identical by descent in the initial scan. One core haplotype of 3 cM was observed in LCCS alleles, supporting the assumption of one major mutation underlying LCCS, and linkage disequilibrium analysis restricted the critical chromosomal region to <100 kb in the vicinity of marker D9S61. Two genes, NGAL (neutrophil gelatinase-associated lipocalin and NOTCH 1, were excluded as causative genes for LCCS

Extended high frequency hearing and history of acute otitis media in 14-year-old children in Finland

We studied the extended high frequency hearing of 573 white, urban, mean 13.8-year-old unselected children in Tampere, Finland. All their ear-related morbidity had been recorded since their birth and they had been examined at the ages of 7 months, 2 years, and some of them at 5 years. The extended high frequency audiometry was measured from 10 to 18 kHz, with 1 kHz steps, and the results were related to the number of attacks of acute otitis media (AOM) (0, 1-2, 3-7 and > or = 8) they had experienced. The mean pure tone hearing thresholds varied from 10.7 dB at 10 kHz to 37.0 dB at 18 kHz in the right ears and between 11.6 dB at 10 kHz and 37.4 dB at 18 kHz in the left ears. Among those with > or = 8 attacks of AOM the the thresholds were highest, the difference between them and each of the first 3 groups being statistically significant at 13 and 14 kHz. From 11 to 16 kHz the same difference was significant between the last (> or = 8 AOM) and at least 2 of the first 3 AOM groups. Numerous attacks of AOM may have a harmful effect on high frequency hearing in the long term.

Hearing and acute otitis media in 13-year-old children

Air and bone conduction thresholds of 330 unselected urban 13-year-old children with a known history of otitis were measured under ideal conditions, using standard clinical audiometry. In the subgroups of children with different numbers (0, 1-2, 3-7, > or = 8) of attacks of acute otitis media (AOM) in their history, the mean air conduction thresholds varied from 0.2 to 11.5 dB at different frequencies in different AOM subgroups. Air conduction pure tone averages (PTA, mean threshold at 0.5, 1 and 2 kHz) > 20 dB were not found in any of the ears. The mean bone conduction thresholds varied from -0.0 to 1.8 dB, depending on the subgroup and frequency (0.25 to 4.0 kHz) studied. Bone conduction PTAs > 10 dB were measured in 5 (0.8%) ears. Single bone conduction thresholds > 10 dB were found at different frequencies in 3 to 15 (0.5 to 2.3%) of the ears, and thresholds > 20 dB in only 2 ears (0.3%). The mean thresholds and number of ears with decreased hearing were distributed equally between different AOM subgroups, except that some air conduction high frequency losses were more frequent in children with > or = 8 attacks of AOM. We conclude that childhood AOM, even if it occurs frequently, seems not to have a significant harmful long-term effect on hearing.

Sensorineural hearing loss and acute otitis media in children

Sensorineural hearing of 359 otoscopically and tympanometrically normal 5-year-old children with known otitis-history was studied under ideal conditions. In the subgroups of children with a different number (0, 1-2, 3-7, greater than or equal to 8) of attacks of acute otitis media (AOM) in their history, the mean bone conduction thresholds unregularly varied from 0.1 dB to 7.4 dB, depending on the frequency and the subgroup studied. The proportion of the ears with a bone conduction threshold greater than 10 dB at 0.5, 1, 2 or kHz ranged, also unregularly, from 10.8% to 0.5%, the greatest percentages being found at 0.5 and 1 kHz in the children without a history of AOM. Thus, neither AOM nor its treatment, even if frequently occurring, seem to cause permanent sensorineural hearing loss in children.

Hearing and hearing loss in 5-year-old children. Pure-tone thresholds and the effect of acute otitis media

Air and bone conduction pure-tone thresholds of 420 unselected urban children were measured with standard clinical audiometry. The mean of air conduction pure-tone averages (average threshold at 0.5, 1 and 2 kHz) was 8.6 dB HL in girls and 8.3 dB HL in boys. In only 5 ears (0.6%), was this average greater than or equal to 35 dB HL. The threshold greater than or equal to 35 dB HL at 4 kHz was found in 1.4% of the ears and at 8 kHz in 4.1%. The bone conduction threshold greater than 20 dB HL at any of the frequencies from 0.5 to 4 kHz was very rare, and only once, at 4 kHz, was it greater than 35 dB HL. Earlier attacks of acute otitis media seemed to have only a marginal long-term effect on air conduction hearing, and an almost negligible effect on bone conduction hearing.

The Bayesian approach to the evaluation of risk factors in acute and recurrent acute otitis media

A multivariant modelling method was used to analyse the risk, associated with 22 different factors, of contracting acute otitis media (AOM) in a prospective cohort of 1294 urban children followed up to the age of 17-32 (mean 25) months. By far the most important risk factor was the caring of the child at a day-care centre. The importance of this factor further increased with increasing recurrence of the attacks. Next in order came the existence of sibling(s) with AOM attacks during the follow-up. Prolongation of breastfeeding increased the protection against AOM during the first year of life. The frequency of AOM attacks was lowest around midsummer and highest in early winter.

Pneumococcal middle ear fluid antibodies after pneumococcal acute otitis media in infants

Forty-one infants, who during their first (initial) acute otitis media (AOM) had culturable S. pneumoniae (Pn) in 57 middle ear fluids (MEFs) which prolonged or recurred during the follow-up, were observed for 7-15 months for the presence of Pn, Pn-antigens (Pn-ags) and initial-type/group Pn-antibodies (Pn-abs) in these MEFs. Initially, Pn-abs were found in only 3 MEFs. During the follow-up a total of 20 ears (35%) were, at various time-intervals, positive for Pn-abs; they belonged to all three major Ig-classes, but were often slight in quantity. Most regularly, and often with distinct positivity, Pn-abs were found to type 3, 9N and 14. Secretory abs were detected in 5 ears. Within one month after initial AOM, Pn-abs appeared in 9 of the 41 ears with MEF (22%); six of them cleared soon after that. MEFs with Pn-abs usually did not show initial-type Pn/Pn-ag, but new Pn/Pn-ag could later be simultaneously present in recurrent MEF. So, pneumococcal AOM may cause a local and/or systemically mediated immune response in the middle ear in infants. The response may protect the ear from homologous, but still be present in apparently non-homologous otitis media.

Incidence of acute otitis media up to the age of 1 1/2 years in urban infants

The object of this prospective cohort investigation of 1,642 infants was to study the incidence of acute otitis media (AOM) in urban children during the first 18 months of life. The monthly incidence of AOM was greatest at the age of 10 months, and the largest proportion of children with AOM was also found in this 10-month age group. Before the age of 18 months, 56.7% of the infants had had at least one episode of AOM, while 26.9% had had one or two episodes and 29.8% three or more. The corresponding figures before the age of 12 months were: 45.3%; 26.8%; 18.5%, and before the age of 9 months: 30.5%; 22.1%; 8.4%. The AOM incidence, particularly as regards recurrent AOM, was rather higher in boys than in girls.

C-reactive protein in acute otitis media

Serum C-reactive protein (CRP) levels were studied in 79 children with acute otitis media (AOM), aged from 4 months to 5 years. The CRP was less than 10 mg/l in 27 children, greater than or equal to 20 mg/l in 34, and greater than or equal to 40 mg/l in 17 children, 25 of the 41 attacks caused by S. pneumoniae or H. influenzae showed a CRP of greater than or equal to 20 mg/l and 15 CRP greater than or equal to 40 mg/l, in 38 cases without major otitis pathogens, the respective figures were 9 (p less than 0.01) and 2 (p less than 0.001). Although statistically significant correlations between otitis-related clinical parameters and CRP levels were rare, there was a tendency toward higher CRP values among those with a more severe clinical picture. All five attacks with CRP greater than or equal to 100 mg/l were bilateral, caused by major pathogens, and preceded by a respiratory infection. They also tended to have high fever and a large amount of fluid in myringotomy. However, even in these the general course of AOM and other morbidity was not different from the others.

Pneumococcal bacteriology after pneumococcal otitis media with special reference to pneumococcal antigens

Fifty-four ears with evidence of pneumococcus (Pn) in the first acute otitis media (AOM) in 38 infants and with prolongation or recurrence of the MEF during the follow-up were observed for 7-22 months for the presence of Pn by culture or of pneumococcal antigen (Pn-ag) by counterimmunoelectrophoresis or latex agglutination methods in their MEFs. During the first three 1-month observation periods, Pn and/or Pn-ags were detected in 24% to 9% of these ears, always of the initial type/group. Later on new Pn types/groups appeared also. In two of the 9 MEFs persisting for greater than or equal to 3 months, initial Pn-ag, with culturable Pn, was repeatedly found but not for longer than 5 months. Of the 12 ears resulting in secretory otitis media (SOM) only one showed initial Pn-ag (and Pn) in the MEF of SOM. Pneumococcal type/group pattern associated with prolongation or recurrence of infection did not differ from that of initial AOM. In another series of 151 SOM ears in 97 children, Pn-ags were detected in 7 MEFs. Four of them grew Pn, each of the corresponding group. Our studies suggest that the persistence of Pn-ags in the middle ear after AOM is limited and their occurrence in the MEFs of SOM is rare. Thus, the role of the persistence of Pn-ags in prolonged, recurrent or secretory otitis media seems questionable.

Prevention of otitis media in children by pneumococcal vaccination

A total of 3,340 infants, 95 per cent of them 7 to 9 months old, were randomly vaccinated in a double-blind fashion with either the 14-valent pneumococcal (Pn) polysaccharide vaccine or a saline placebo in three urban areas in Finland. The second dose of the vaccine was given 5 months later. Age and sex distribution, recruitment of infants, and their otitis-related treatment and follow-up were similar in the study areas. Side effects after vaccination were mild and fewer than among older children. Antibody responses to vaccine polysaccharides varied from type to type, but were generally poor, especially to types most prevalent in otitis media. After the first dose of vaccine, the occurrence of otitis visits among the Pn-vaccinated, as compared with controls, showed inter-area differences, but ranged from not more than a 30 per cent reduction at its best to an increase in some areas and in some clinical categories. The respective figures for children with acute otitis media were similar between the vaccination groups and the study areas. The effect of the vaccine on acute otitis media caused by specific Pn types/groups represented in the vaccine was variable but generally poor. Group 6 attacks especially seemed to behave problematically. The second dose of the vaccine did not give additional benefit serologically or clinically. The efficacy of currently available pneumococcal vaccine against otitis media seemed poor in infants.

Branhamella catarrhalis in acute otitis media

A total of 5217 middle ear fluid (MEF) samples obtained from 1203 children with otitis media, aged 3 months to 6 years, were studied for the presence of Branhamella catarrhalis (Br) between Oct. 1977 and Sept. 1981. Br grew in 10.2% of 3497 MEFs of acute otitis media (AOM), with almost the same frequency in the very first and subsequent attacks. During the first 4 years of life the percentage did not vary much; among older children it seemed to decrease. The overall prevalence of Br in AOM did not change during the study period. Br alone grew in 72.4% of acute MEFs with Br; with other bacteria the respective figure was 82.9% (p less than 0.001). Acute attacks with bilateral Br were found in 22.8% of attacks with Br. In 1720 non-acute MEFs obtained at postacute control visits, Br was isolated in only 7.0%. The proportion of beta-lactamase-producing strains among the 2419 otitis-Br strains tested in two laboratories of the two study regions showed an increase from 27.1% and 21.1% in 1980 to 57.6% and 38.6% in 1983, respectively (p less than 0.001).

Haemophilus influenzae in acute otitis media

We studied the occurrence of Haemophilus influenzae (Hi) in 2625 middle ear fluid (MEF) specimens obtained from 523 children with otitis media, aged 3 months to 6 years, between October 1977 and May 1979. In clinically acute cases 12.3% of the MEFs grew Hi; 6.3% (13/206) of the strains were of type b and 4.9% (10/206) were beta-lactamase producing. In the very first acute case of a child 8.0% (21/263) of the MEFs grew Hi, but in acute recurrences it was cultured in 17.0% (184/1082) (p less than 0.001). In non-acute persistent MEFs obtained during control visits Hi was found in no less than 21.7% (198/913); as many as 12.6% (25/198) of them were beta-lactamase producing. Both of these figures, but not the proportion of type b strains (8.6%), were significantly (p less than 0.001 and p less than 0.01, respectively) greater than in clinically acute MEFs. Hi was grown in 13.1% of the acute MEFs taken from children less than 4 years old, but in only 8.6% of the older children (p less than 0.05). The annual survey of all the 1816 Hi strains isolated from the MEFs of acute or subacute cases of otitis media in one laboratory in 1976-81 showed the proportion of beta-lactamase producing strains of all Hi strains to be gradually increasing from 8.0% (17/212) in 1976 to 15.2% (16/105) in 1981 (p less than 0.05).

Occurrence and recurrence of acute otitis media among children

The occurrence and recurrence of acute otitis media among 37 570 Finnish children at risk who were under 15 years of age were studied. During a one-year period, 4 337 of the children experienced a total of 6 249 attacks of acute otitis media, giving an annual incidence rate of 16.6%. The highest incidence, 75.5%, was found among infants 6--11 months old. 50% of Finnish children had experienced at least one ear infection before their third birthday and 75% before the age of 10, and among this latter group the total number of otitis attacks per child-year during a lifetime was 0.71. Among children under 10, half of the index attacks were recurrences, and among children under 16, 28% of the index attacks were followed by recurrences during the study year. The highest relative recurrence rate was found during the second year of life. Before the second birthday both incidence and recurrence rates were significantly (p less than 0.001) higher among boys. Acute otitis media was most common in the higher social class families and the lowest incidence and recurrence rates were found among children of farmers.

Incidence of acute otitis media

The occurrence of acute otitis media was studied over a one-year period in a total population of 146822 persons living in different parts of Finland. Of these 146822 persons, 4583 experienced a total of 6518 otitis attacks giving an annual incidence rate of 4.44% (4.48% in males and 4.07% in females, P less than 0.001). Acute otitis media was strikingly concentrated in the youngest age groups, with the highest annual incidence rates, in the order of 50%, found in infants younger than 2 years. Half of all the episodes occurred before the age of 33 months. The relative risk of getting acute otitis media was about 200 times higher during the first 2 years of life than as an adult. The occurrence of otitic episodes followed seasonal variations, and in urban areas the incidence was significantly (P less than 0.001) higher than in the countryside.