A diary study on a random sample of 625 Swiss children aged 0 to 5 yr was conducted in two cities in Switzerland to investigate the association between air pollution and respiratory symptoms. Total suspended particulates (TSP), SO2 and NO2 were measured by city monitor. In addition, passive samplers inside and outside the home measured NO2 concentration during the 6 wk each child was on the diary. Diaries were filled out by parents, and 20% were validated with the attending pediatrician's case notes. Incidence and duration of symptom episodes were examined separately. The study included any episode, episodes of coughing without runny nose, upper respiratory episodes, and episodes of breathing difficulty. In regressions using 6-wk average pollution that controlled for medical history, NO2 measured outdoors but not indoors was associated with the duration of any symptom. Total suspended particulates were a more significant predictor of duration of any symptom than NO2. The 6-wk average TSP was significantly associated with incidence of coughing episodes and marginally significant as a predictor of upper respiratory episodes. Previous day's TSP was a significant predictor of incidence of upper respiratory symptoms. Annual average of NO2 was associated with the duration of any episode and of upper respiratory episodes. We conclude that the incidence and duration of respiratory symptom episodes are likely associated with particulate concentrations and duration may be associated with NO2.

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This document presents a critical evaluation of the equilibrium constants and reaction enthalpies for the complex formation reactions between aqueous Hg(II) and the common environmental inorganic ligands Cl–, OH–, CO32–, SO42–, and PO43–. The analysis used data from the IUPAC Stability Constants database, SC-Database, focusing particularly on values for 25 °C and perchlorate media. Specific ion interaction theory (SIT) was applied to reliable data available for the ionic strength range Ic < 3.0 mol dm–3. Recommended values of log10βp,q,r° and the associated reaction enthalpies, ∆rHm°, valid at Im = 0 mol kg–1 and 25 °C, were obtained by weighted linear regression using the SIT equations. Also reported are the equations and specific ion interaction coefficients required to calculate log10βp,q,r° values at higher ionic strengths and other temperatures. A similar analysis is reported for the reactions of H+ with CO32– and PO43–. Diagrams are presented to show the calculated distribution of Hg(II) amongst these inorganic ligands in model natural waters. Under typical environmental conditions, Hg(II) speciation is dominated by the formation of HgCl2(aq), Hg(OH)Cl(aq), and Hg(OH)2(aq).

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Complex formation between Pb II and the common environmental inorganic ligands, Cl -, OH -, CO 3 2-, SO 4 2-, and PO 4 3-, can be significant in natural waters with low concentrations of organic matter. Numerical modeling of the speciation of Pb II amongst these inorganic ligands requires reliable values for the relevant stability (formation) constants. This paper provides a critical review of such constants and related thermodynamic data. It recommends values of log 10 β p,q,r°v alid at I m = 0 mol kg -1 and 25 °C (298.15 K), along with the equations and empirical coefficients required to calculate log 10 β p,q,r values at higher ionic strengths using the Brønsted-Guggenheim-Scatchard specific ion interaction theory (SIT). Some values for reaction enthalpies, Δ r H, are also reported.In weakly acidic fresh water systems (-log 10 {[H + ]/c°} < 6), the speciation of Pb II is similar to that of Cu II . In the absence of organic ligands, Pb II speciation is dominated by Pb 2+ (aq), with PbSO 4 (aq) as a minor species. In weakly alkaline solutions, 8.0 < -log 10 {[H + ]/c°} < 9.0, the speciation is dominated by the carbonato species PbCO 3 (aq) and Pb(CO 3 ) 2 2-. In weakly acidic saline systems (-log 10 {[H + ]/c°} < 6), the speciation is dominated by PbCl n (2-n)+ complexes, (n = 0-3), with Pb 2+ (aq) as a minor species. In this medium (and in seawater), the speciation contrasts with that of Cu II because of the higher stability of the Pb 2+ -chlorido-complexes. In seawater at -log 10 {[H + ]/c°} = 8.2, the calculated speciation is less well defined, although it is clearly dominated by the uncharged species PbCO 3 (aq) (41 % of [Pb] T ) with a significant contribution (16 %) from Pb(CO 3 )Cl -and minor contributions (5-10 %) from PbCl n (2-n)+ , (n = 0-3) and Pb(CO 3 ) 2 2-. The uncertainty in calculations of Pb II speciation in seawater arises from (a) the large uncertainty in the stability constant for the apparently dominant species PbCO 3 (aq), (b) the reliance on statistical predictions for stability constants of the ternary species Pb(CO 3 )Cl -and Pb(CO 3 )OH -, and (c) the uncertainty in the stability constant for PbCl 4 2-, the available value being considered