Neuropsychological effects of chronic low-dose exposure to polychlorinated biphenyls (PCBs): A cross-sectional study

BACKGROUND: Exposure to indoor air of private or public buildings contaminated with polychlorinated biphenyls (PCBs) has raised health concerns in long-term users. This exploratory neuropsychological group study investigated the potential adverse effects of chronic low-dose exposure to specific air-borne low chlorinated PCBs on well-being and behavioral measures in adult humans. METHODS: Thirty employees exposed to indoor air contaminated with PCBs from elastic sealants in a school building were compared to 30 non-exposed controls matched for education and age, controlling for gender (age range 37–61 years). PCB exposure was verified by external exposure data and biological monitoring (PCB 28, 101, 138, 153, 180). Subjective complaints, learning and memory, executive function, and visual-spatial function was assessed by standardized neuropsychological testing. Since exposure status depended on the use of contaminated rooms, an objectively exposed subgroup (N = 16; PCB 28 = 0.20 μg/l; weighted exposure duration 17.9 ± 7 years) was identified and compared with 16 paired controls. RESULTS: Blood analyses indicated a moderate exposure effect size (d) relative to expected background exposure for total PCB (4.45 ± 2.44 μg/l; d = 0.4). A significant exposure effect was found for the low chlorinated PCBs 28 (0.28 ± 0.25 μg/l; d = 1.5) and 101 (0.07 ± 0.09 μg/l; d = 0.7). Although no neuropsychological effects exceeded the adjusted significance level, estimation statistics showed elevated effect sizes for several variables. The objectively exposed subgroup showed a trend towards increased subjective attentional and emotional complaints (tiredness and slowing of practical activities, emotional state) as well as attenuated attentional performance (response shifting and alertness in a cued reaction task). CONCLUSION: Chronic inhalation of low chlorinated PCBs that involved elevated blood levels was associated with a subtle attenuation of emotional well-being and attentional function. Extended research is needed to replicate the potential long-term low PCB effects in a larger sample

Ectomycorrhizal Helper Bacteria: The Third Partner in the Symbiosis

In natural conditions, mycorrhizal fungi are surrounded by complex microbial communities, which may trigger various responses, from enhancement of the establishment of mycorrhizal symbiosis to mycelial growth inhibition or cell death. The symbiosis between mycorrhizal soil fungi and higher plants takes advantage of active collaboration with specific helper bacteria. Thus, a symbiosis so far thought of involving two components could be the result of the interaction among at least three different partners. This chapter focuses on the relationship between edible ectomycorrhizal mushrooms and soil bacteria, in particular nitrogen-fixing bacteria associated with Tuber species. The ability of these bacteria to modify nutrient availability during the fructification phase is very important to truffle development. This chapter will also discuss perspectives on the beneficial use of ectomycorrhizal symbiosis with nitrogen-fixing bacteria to develop predictive models that could be used to improve the mycorrhization processes with the further aim of obtaining plants infected with Tuber magnatum Pico, the most economically important truffle species that remains difficult to cultivat