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Polychlorinated biphenyls. Indoor air contamination due to thiokol-rubber sealants in an office building

The paper presents results of statistical analyses of indoor PCB air concentrations related to building characteristics, time trends and resident behavior. More than 150 measurements of air concentrations were made in five high-rise apartment buildings with PCB containing sealants in an estate in Denmark. The indoor air concentrations consists of two datasets. Data set A are short-term nighttime measurements in both kitchen and living room taken during the period from 2010 to 2017. Data set B consists of 24-h measurement taken in the living room late 2017. Data set B also holds information from a questionnaire of among other things cleaning habits filled out by the residents and concentrations of PCB in dust from the vacuum cleaner bag of the homes. Both data sets show higher air concentrations associated with higher indoor temperature. Data set A further show, that this was associated with wintertime and it is speculated, that the higher air concentrations in cold weather are due to underfloor PCB sources being heated by radiator pipes. Building, floor level and apartment type were used as variable as the apartments were very similar and the type included many characteristic parameters. No relations were seen between air concentrations and these parameters. Repeated measurements of air concentrations from a number of apartments between 2010 and 2017 showed some variation over time, though no clear tendency was observed. Frequent cleaning habits had a minor influence on lowering the air and dust concentrations.

Efficient and environmentally friendly methods for the remediation of polychlorinated biphenyls (PCBs)-contaminated wastewater have become an important issue. In this study, persulfate (PS) was activated with sodium thiosulfate (TS) to degrade 2,2′-dichlorobiphenyl (DCB) at an extraordinarily high rate at pH ≤ 4.0 at room temperature. The PS/TS system exhibited much higher activity than systems with PS or TS alone at pH 2.0: 90.3% DCB was removed within 120 min, a much higher removal rate than those of the latter systems. Sulfate radical (SO₄⁻) was verified to be the main reactive substance through scavenging and trapping experiments; sulfate radicals can decompose and detoxify DCB by dechlorination and hydroxylation processes. The removal efficiency of DCB (58.5% in 120 min) was also satisfactory in the TS system, in which TS could perform nucleophilic substitution on the DCB molecule at pH ≤ 4.0, followed by DCB dechlorination and the generation of hydroxy-biphenyl. Plausible mechanisms and reaction pathways involving nucleophilic substitution in the TS system and the formation of reactive oxygen species (ROS) in the PS/TS system to attack the carbon atom on DCB were proposed and calculated by density functional theory (DFT). The presence of Cl⁻, NO₃⁻, HCO₃⁻ and humic acid (HA) may have inhibited the removal of DCB in the PS/TS system, while the effect was not significant in the TS system. Our work introduces novel and rapid removal methods for the removal of PCBs and may be significant for the development of efficient strategies for halogenated pollutant control in real water.

As part of an investigation of the total indoor exposure of residents in PCB contaminated apartments in a building estate in Denmark, 73 homes were visited. Samples of air, vacuum cleaner dust and surface wipes were taken and analysed for 15 PCB congeners. The 53 apartments located in high-rise buildings with indoor PCB containing sealants showed significant elevated total concentrations of PCB in air, dust and surface wipes compared to 20 reference homes. The average concentration in exposed homes was 2330 ng PCB_total/m³ in air, 12.000 ng PCB_sum15/g in dust and for surface wipes 529 ng PCB_sum15/wipe. These values were respectively 40, 25 and 50 times higher than the averages found in reference homes. The air concentration in all exposed homes was higher than the lower recommended action level of 300 ng PCB_total/m³ from the Danish Health Authority, whereas all reference homes were below. The air concentrations in exposed homes were variating, partly due to indoor temperature. The concentrations in air and dust samples were significantly correlated for PCB_sum7 in exposed homes. No significant correlation was observed between samples of air and surface wipes, despite surface wipes from exposed homes were significantly different from wipes taken in reference homes. Both dust samples and surface wipes have a potential as screening tool for identifying elevated levels of the less chlorinated PCBs in air. Additional short-term measurements of air concentrations in a subgroup of exposed homes indicated limited diurnal variations within the individual homes. The congener patterns were rather uniform within the respective media from the exposed homes and dominated by tri- and tetraPCBs. The pattern of air differed from that of dust and surface wipes, which were more alike. The study demonstrates a wide spread PCB contamination of the indoor environment in buildings with PCB in indoor sealants and confirms the need for identifying and alleviate PCB in buildings causing a health concern to the occupants.

Paired indoor air and floor dust samples were collected from residential houses and offices (n = 28) in two Australian cities in 2015. For the air samples, a modified passive air sampler (PAS) was used to collect semi-volatile organic compounds (SVOCs) in gaseous phase and airborne particles simultaneously. Sampling rates (R) of the PAS for gaseous SVOCs ranged from 0.69 to 3.4 m³ sampler⁻¹ day⁻¹. Out of the 33 analytes, 22, 14 and 17 compounds were detected (above the method detection limit) in over 50% of air, airborne particles and floor dust samples respectively. The highest median level in air, airborne particles and floor dust was observed for phenanthrene (2.0 ng m⁻³), permethrin (8800 ng g⁻¹) and permethrin (5100 ng g⁻¹) respectively. Among polychlorinated biphenyl (PCB) congeners, with few exceptions, the largest contribution was from 3,3′-dichlorobiphenyl (PCB11) for both indoor air and floor dust samples. In these houses and offices, the indoor level of polycyclic aromatic hydrocarbons (PAHs) was mainly influenced by ambient (outdoor) air. Primary sources of PCBs were from within indoor environments and generally older houses have higher concentrations in air. Among pesticides, hexachlorobenzene in indoor environments appeared to be due to transfer from outdoor sources whereas chlordanes and pyrethroids were associated with past and current household application respectively. Compared to data from other countries/regions, concentrations of chlordanes, chlorpyrifos and pyrethroids in indoor air and dust samples from Australia were among the highest whereas PCB and PAH levels were among the lowest. The sum of estimated daily intakes (EDIs) via inhalation and dust contact and ingestion were calculated. The highest median value of EDI was observed for permethrin at 2.8 (for adults) and 74 ng kg⁻¹ day⁻¹ (for toddlers), which are <0.15% of the U.S. EPA reference dose.

Buildings contaminated with polychlorinated biphenyls (PCBs) are a health concern for the building occupants. Inhalation exposure is linked to indoor air concentrations of PCBs, which are known to be affected by indoor temperatures. In this study, a highly PCB contaminated room was heated to six temperature levels between 20 and 30  C, i.e. within the normal fluctuation of indoor temperatures, while the air exchange rate was constant. The steady-state air concentrations of seven PCBs were determined at each temperature level. A model based on Clausius–Clapeyron equation, ln(P) = −ΔH/RT + a₀, where changes in steady-state air concentrations in relation to temperature, was tested. The model was valid for PCB-28, PCB-52 and PCB-101; the four other congeners were sporadic or non-detected. For each congener, the model described a large proportion (R²>94%) of the variation in indoor air PCB levels. The results showed that one measured concentration of PCB at a known steady-state temperature can be used to predict the steady-state concentrations at other temperatures under circumstances where e.g. direct sunlight does not influence temperatures and the air exchange rate is constant. The model was also tested on field data from a PCB remediation case in an apartment in another contaminated building complex where PCB concentrations and temperature were measured simultaneously and regularly throughout one year. The model fitted relatively well with the regression of measured PCB air concentrations, ln(P) vs. 1/T, at varying temperature between 16.3 and 28.2 °C, even though the measurements were carried out under uncontrolled environmental condition.

The emissions of polychlorinated biphenyl (PCB) congeners from thirteen caulk samples were tested in a micro-chamber system. Twelve samples were from PCB-contaminated buildings and one was prepared in the laboratory. Nineteen light ballasts collected from buildings that represent 13 different models from five manufacturers were tested in 53-L environmental chambers. The rates of PCB congener emissions from caulking materials and light ballasts were determined. Several factors that may have affected the emission rates were evaluated. The experimentally determined emission factors showed that, for a given PCB congener, there is a linear correlation between the emission factor and the concentration of the PCB congener in the source. Furthermore, the test results showed that an excellent log-linear correlation exists between the normalized emission factor and the vapor pressure (coefficient of determination, r² ⩾ 0.8846). The PCB congener emissions from ballasts at or near room temperature were relatively low with or without electrical load. However, the PCB congener emission rates increased significantly as the temperature increased. The results of this research provide new data and models for ranking the primary sources of PCBs and supports the development and refinement of exposure assessment models for PCBs.