Characterizing worker exposure to bitumen during hot mix paving and asphalt mixing operations

A survey of bitumen exposure was carried out during hot mix paving and asphalt mixing. Four methods of characterizing and quantifying bitumen fume in inhalable particles were used: gravimetric, infrared spectroscopy, gas chromatography, and total absorbance (of the particle filter surface). Dermal deposition of bitumen was assessed by determination of cyclohexanesoluble matter in the material collected by paper or cotton pads worn on the inside of a person's wrists. The researchers studied the correlation patterns between results of these methods using pairwise correlation coefficients and principal component analysis (for air concentrations only). For hot mix paving, within- and between-worker variance components were evaluated, adjusting for area paved. Collected fume was dark in color and mainly consisted of aliphatic hydrocarbons of less than 20 carbon atoms. Inconsistent correlation patterns between dermal deposition and air levels were observed. Quantification of organic matter using either infrared spectroscopy or gas chromatography appeared to be good methods for monitoring inhalable bitumen fume. Cotton pads seem to be more promising than paper pads for measuring dermal exposure during paving. Paving workers were uniformly exposed to bitumen fume. Assessment of the uniformity of dermal exposure depended on the type of pad used. Day-to-day variability and intensity of inhalable and dermal bitumen exposures depended on area paved. The small size of the study limits the potential application of the results to the asphalt industry in general. More research is needed to develop a valid and inexpensive method of assessing total bitumen exposure.     

B lymphocytes on the front line of autoimmunity

The paradigm that B cell response to self antigens (Ag) is promoted by antibodies (Ab) has become unsatisfactory. Studies over the last decade have indeed revealed that B cells serve extraordinarily diverse functions within the immune system other than Ab production. They normally play a role in the development in the regulation, as well as the activation of lymphoid architecture, regulating dentritic cells and T cell subsets function through cytokine production. Receptor editing is also essential in B cells and aids in preventing autoimmunity. Both abnormalities in the distribution of B cells subsets and clinical benefit response to B cell depletion in autoimmune states illustrate their importance. Transgenic animal models have demonstrated that sensitivity of B cells to Ag receptor cross-linking correlates to autoimmunity: negative signaling by CD5 and CD22 in maintaining tolerance through recruitment of phosphatase has thus been documented. In short, a new area has been reached, whereby B lymphocytes return as a significant contributor to autoimmune disorders.     

TLR9 responses of B cells are repressed by intravenous immunoglobulin through the recruitment of phosphatase

One way for intravenous Ig (IVIg) to affect responses of the B cells might be to operate through their TLR7 and TLR9. We confirm the ability of TLR agonists to induce CD25 expression in B cells. For this to occur, sialylated Fc-gamma of IgG included in the IVIg preparation are required. As a result, IVIg suppresses TLR-induced production of the proinflammatory IL-6, but not that of the anti-inflammatory IL-10. That is, IVIg mimics the effects of the MyD88 inhibitor. Finally, as we previously showed that IVIg induces CD22 to recruit the inhibitory SHP-1, we established that this enzyme was also involved in IVIg-induced inhibition of TLR9 signaling. This is the first report to demonstrate such a mechanism underlying the negative impact of IVIg on B lymphocytes.