Immune cell counts and risks of respiratory infections among infants exposed pre- and postnatally to organochlorine compounds: a prospective study

<p>Abstract</p> <p>Background</p> <p>Early-life chemical exposure may influence immune system development, subsequently affecting child health. We investigated immunomodulatory potentials of polychlorinated biphenyls (PCBs) and <it>p,p'</it>-DDE in infants.</p> <p>Methods</p> <p>Prenatal exposure to PCBs and <it>p,p'</it>-DDE was estimated from maternal serum concentrations during pregnancy. Postnatal exposure was calculated from concentrations of the compounds in mother's milk, total number of nursing days, and percentage of full nursing each week during the 3 month nursing period. Number and types of infections among infants were registered by the mothers (N = 190). White blood cell counts (N = 86) and lymphocyte subsets (N = 52) were analyzed in a subgroup of infants at 3 months of age.</p> <p>Results</p> <p>Infants with the highest prenatal exposure to PCB congeners CB-28, CB-52 and CB-101 had an increased risk of respiratory infection during the study period. In contrast, the infection odds ratios (ORs) were highest among infants with the lowest prenatal mono-<it>ortho </it>PCB (CB-105, CB-118, CB-156, CB-167) and di-<it>ortho </it>PCB (CB-138, CB-153, CB-180) exposure, and postnatal mono- and di-<it>ortho </it>PCB, and <it>p,p'</it>-DDE exposure. Similar results were found for pre- and postnatal CB-153 exposure, a good marker for total PCB exposure. Altogether, a negative relationship was indicated between infections and total organochlorine compound exposure during the whole pre- and postnatal period. Prenatal exposure to CB-28, CB-52 and CB-101 was positively associated with numbers of lymphocytes and monocytes in infants 3 months after delivery. Prenatal exposure to <it>p,p'</it>-DDE was negatively associated with the percentage of eosinophils. No significant associations were found between PCB and <it>p,p'</it>-DDE exposure and numbers/percentages of lymphocyte subsets, after adjustment for potential confounders.</p> <p>Conclusion</p> <p>This hypothesis generating study suggests that background exposure to PCBs and <it>p,p'</it>-DDE early in life modulate immune system development. Strong correlations between mono- and di-<it>ortho </it>PCBs, and <it>p,p'</it>-DDE exposures make it difficult to identify the most important contributor to the suggested immunomodulation, and to separate effects due to pre- and postnatal exposure. The suggested PCB and <it>p,p'</it>-DDE modulation of infection risks may have consequences for the health development during childhood, since respiratory infections early in life may be risk factors for asthma and middle ear infections.</p

Extraction of galactoglucomannan from thermomechanical pulp mill process water by microfiltration and ultrafiltration-Influence of microfiltration membrane pore size on ultrafiltration performance

Galactoglucomannan is the major hemicellulose in process water from thermomechanical pulping of spruce. The recovery of hemicelluloses from this process water would both reduce the load on pulp mill water treatment plants and yield a biopolymer suitable as a raw material for renewable products. One method of recovering these hemicelluloses is two-stage filtration employing microfiltration to remove large contaminants, such as suspended matter and colloidal extractives, followed by ultrafiltration to concentrate and purify the hemicelluloses from low molecular mass contaminants. This investigation shows that a microfiltration membrane with a pore size of 0.1μm removes colloidal extractives while still maintaining a high amount of high molecular mass hemicelluloses in the microfiltration permeate. The removal of extractives resulted in an increase in the initial flux during the subsequent ultrafiltration step from 90 L/m2h to over 200 L/m2h

Influence of air and nitrogen sparging on flux during ultrafiltration of hemicelluloses extracted from wheat bran

Ultrafiltration can be used to concentrate arabinoxylan isolated from wheat bran. Prefiltration with diatomaceous earth and air sparging during ultrafiltration of the alkaline hemicellulose solution were both found to increase the flux, while nitrogen sparging had no effect. The flux of the untreated solution was 51 L/m2 h, while the flux after prefiltration of the solution with diatomaceous earth was 62 L/m2 h. After 5 h of air sparging during ultrafiltration of the prefiltered solution the flux was 230 L/m2 h. However, sparging the prefiltered solution with nitrogen gas had no effect on the flux. This shows that the increase in flux was not due to the reduction of concentration polarization by sparging per se. Size-exclusion chromatography showed that sparging with air caused a reduction in the size of hemicelluloses >100 kDa to 10–100 kDa, which is believed to be due to oxidative degradation of hemicelluloses. This size reduction of the hemicelluloses is likely the main cause of the increased flux. The retention of hemicelluloses during ultrafiltration with a ceramic membrane with a nominal cut-off of 10 kDa was 96% in all experiments, except at the end of the experiment with the prefiltered, air-sparged solution, when the retention decreased to 93% due to the size reduction of the hemicelluloses. Air sparging seems to be an efficient flux enhancing method with limited negative influence on the molecular size of hemicelluloses

Techno-economic impact of air sparging prior to purification of alkaline extracted wheat bran hemicelluloses by membrane filtration

Air sparging of alkaline-extracted wheat bran hemicelluloses prior to ultrafiltration has been shown to increase the flux. The techno-economic impact of air sparging on the cost of concentration and purification of wheat bran hemicelluloses by ultrafiltration and diafiltration was studied in this work. Two alkaline hemicellulose solutions were purified until the conductivity of the diafiltration permeate was <1 mS/cm. Both solutions were pretreated by the removal of suspended matter using dead-end filtration with diatomaceous earth as filter aid. One of the solutions was further pretreated by air sparging for 4 h at 80 °C prior to concentration by ultrafiltration. Air sparging increased the average flux during ultrafiltration from 52 L/m2 h to 151 L/m2 h, and during diafiltration from 46 L/m2 h to 130 L/m2 h. A higher diafiltration factor was needed for the air-sparged solution, requiring a higher amount of diafiltration water. However, the cost of purifying the hemicelluloses was reduced from 1375 €/ton hemicelluloses to 1122 €/ton by sparging the solution with air prior to membrane filtration

Enzymatic treatment of hemicelluloses and lignin isolated from thermomechanical pulp mill process water

Hemicelluloses dissolved in thermomechanical pulp (TMP) mill process streams can be used to manufacture high-value-added products. The molecular mass of the dissolved hemicelluloses is about 10 kDa. In some applications, it would be beneficial with larger molecules. It was therefore investigated whether it is possible to increase the size of hemicelluloses isolated by microfiltration and ultrafiltration from TMP process water using enzymatic treatment with laccase. No significant increase of the size of hemicelluloses was achieved, probably due to only a small percentage of lignin carbohydrate complexes in the process water. The molecular mass of lignin increased however markedly from a peak molecular mass of 1 kDa to about 60 kDa. Diafiltration was used to purify large molecules after the enzymatic treatment. Low-molecular-mass sugar and lignin molecules in the diafiltration permeate were concentrated by nanofiltration. The retention of sugars and lignin was about 98% during nanofiltration to a volume reduction of 80%. Average flux during nanofiltration was 49 l/m2 h

On-Site Recovery of Hemicelluloses from Thermomechanical Pulp Mill Process Water by Microfiltration and Ultrafiltration

During mechanical defibration of wood, a minor fraction of the wood mass is dissolved in the process water. These dissolved substances represent an extra energy demand when they are treated in the mill’s wastewater treatment plant. Galactoglucomannan, the main hemicellulose in spruce, can be recovered from thermomechanical pulp mill process water by a process based on microfiltration (MF) and ultrafiltration (UF). The purpose of this work was to study the scale-up of the process from laboratory scale to continuous industrial scale. MF was first studied in the laboratory, and then combined with UF in a continuous pilot process on-site at a pulp mill. The data obtained were used to estimate the cost of the membrane processes for galactoglucomannan recovery which was found to be about €1160 per ton hemicelluloses

Centrifugation as pretreatment before ultrafiltration of hemicelluloses extracted from wheat bran

Hemicelluloses recovered by alkaline extraction of wheat bran can be isolated and purified by ultrafiltration and used to produce high-value products such as barrier films for food packaging. The flux during ultrafiltration depends to a large extent on the pretreatment of the solution. It has been shown previously that dead-end filtration with kieselguhr can increase the flux during ultrafiltration. In the present study, pretreatment by centrifugation and a combination of centrifugation and dead-end filtration was compared with dead-end filtration alone. Centrifugation reduced the turbidity and viscosity of the solution but did not significantly improve the flux during ultrafiltration. The flux of the untreated and the centrifuged solutions was about 65 l/m2 h at 1 bar transmembrane pressure. The flux after dead-end filtration was 150 l/m2 h. After combining centrifugation and dead-end filtration the flux was 200 l/m2 h. In addition to the higher UF flux, filtration resistance during dead-end filtration was markedly reduced after pre-centrifugation of the solution

Reduction of energy demand by use of air sparging during ultrafiltration of alkali-extracted wheat bran hemicelluloses

The flux during membrane filtration can be enhanced by the use of a two-phase gas–liquid flow. This has been shown to be an energy-efficient alternative to increasing the cross-flow velocity. In this work, air sparging was used to increase the flux during ultrafiltration of alkali-extracted wheat bran hemicelluloses. Batch filtration was performed in a pilot unit with a ceramic ultrafiltration membrane with a nominal cut-off of 10 kDa. Parametric studies with and without air sparging were performed at temperatures of 30 °C, 50 °C and 80 °C and cross-flow velocities of 1, 3, 5 and 7 m/s. The limiting flux was not affected by air sparging at 30 °C, while a slight increase was observed at 50 °C and a considerable increase was obtained at 80 °C. Air sparging reduced the energy demand per m3 permeate produced during dead-end batch ultrafiltration at 80 °C and 1 m/s from 0.96 kWh/m3 to 0.51 kWh/m3

Evaluation of membrane performance and cost estimates during recovery of sodium hydroxide in a hemicellulose extraction process by nanofiltration

The recovery the alkaline solvent from of a residual stream after the extraction of hemicelluloses in wheat bran was investigated. The solution was withdrawn from an ultrafiltration (UF) process in which hemicelluloses were recovered. The UF permeate, containing mainly NaOH, lignin and mono- and oligosaccharides, was treated by nanofiltration (NF). Seven NF membranes were tested in a parametric study, and the two membranes showing the best performance were further evaluated in a concentration study. The mean flux of a Koch SelRO MPF 36 and a Microdyn-Nadir NP010 membrane was about 200 l/m2 h during concentration to a volume reduction of 0.75. The retention of NaOH was 95%, respectively. Cost estimates for a NaOH recovery process indicated that an NF plant would have a pay-back time of less than 2 months if the plant was run continuously, and 7 months if it was used 25% of the time