The toxicology of chrysotile-containing brake debris: implications for mesothelioma

Abstract

The global use of “asbestos” in various commercial products has led to a wide range and pervasive legacy of disease. One such use of chrysotile asbestos was brake pads and was utilized commonly in automobiles and heavy vehicles. The result of incorporation of chrysotile into brake pads is associated with the exposure of mechanics fitting and servicing vehicles to liberated chrysotile fibers. Despite the proven exposure, the relative risk of malignant mesothelioma (MM) in this occupational population is broadly seen as low. The toxicity of particulates, including fibers such as chrysotile, is driven by a combination of dose and physicochemical properties. As such, it is plausible that chrysotile released from brake pads may have undergone modification, thereby altering the pathogenicity profile. The impact of high sheer stress causing shortening of long fibers, heat modification, binding of resin matrix to the fiber surface on the relative toxicity of brake debris with regards to MM is considered. It is apparent that released chrysotile can undergo significant modification, reducing the long fiber dose although not all modifications may lead to reduced toxicity.     

Doctor when can I drive? Braking response after knee arthroplasty: A systematic review & meta-analysis of brake reaction time

BackgroundThere is limited evidence available on return to driving for patients undergoing knee arthroplasty (KA). Primarily, surgeons have used brake reaction time as a surrogate measure of safe return to driving. The purpose of this study was to review existing literature and provide guidance on the recovery of braking performance following knee arthroplasty.MethodsA literature search was performed for prospective studies on driving after KA. Two reviewers screened citations for inclusion, assessed methodological quality, and extracted data. Values for total brake reaction-time (TBRT), movement-time (MT), reaction-time (RT), and braking-force (BF) were included for meta-analysis.ResultsTwelve studies with 368 subjects were identified. TBRT, RT, MT, and BF relative to preoperative baseline were assessed. Meta-analysis of TBRT showed a significant improvement from preoperative baseline at 3 months & 1 year (p = 0.003 & p = 0.0001). MT showed a significant increase at 2 and 4 weeks (p = 0.00001 & p = 0.03) before returning to no being significantly different at 6 weeks and beyond. In contrast RTs were noted to improve significantly 2 weeks (p = 0.006), 4 weeks (p = 0.03), and 1 year (p = 0.0002).ConclusionMeta-analysis showed no significant difference in TBRT up until 3 months. RT increased significantly post-operatively suggesting it is not a reliable indicator. MT in contrast was significantly decreased post KA and may represent a more reliable measure of braking performance post KA. Surgeons should consider these recommendations and other patient factors that determine fitness to drive prior to advising their patients on a safe to return to driving.     

Effects of tianeptine and mianserin on car driving skills

RATIONALE: Tianeptine is a novel antidepressant which enhances the reuptake of serotonin (5-HT). Previous studies suggest that tianeptine has a non-sedative side-effect profile, but its effects on everyday activities including car driving have not been fully explored. OBJECTIVES: To assess the effects of tianeptine on tests related to car driving performance. METHOD: Sixteen healthy volunteers received acute doses of tianeptine 12.5 mg and 37.5 mg, mianserin 30 mg and placebo in a double blind four-way crossover study. The effects of treatment on self assessed ratings of sedation (LARS), two valid and reliable laboratory performance measures, critical flicker fusion (CFF) and choice reaction time (CRT) and an "on-the-road" measure of one aspect of car driving performance, brake reaction time (BRT) were examined. The BRT test was administered at baseline and at 1.5, 3, 4.5 and 6 h post-dose, while LARS, CFF and CRT were administered at baseline and at 1, 2, 4 and 5 h post-dose. For all data, the maximum change from baseline was calculated and used in the analysis. RESULTS: Tianeptine had no measurable effect on performance, compared to placebo, on any of the variables investigated. Compared to placebo, mianserin was shown to lower CFF thresholds (P = 0.01), increase reaction times on both the CRT (P = 0.001) and the BRT (P = 0.01) tests and was subjectively rated as more sedative than placebo (P = 0.01). CONCLUSION: The apparent lack of counter-therapeutic side-effects produced by an acute dose of tianeptine suggest that it may be a suitable antidepressant for use in an ambulant population.     

Evaluation of the deposition,translocation and pathological response of brake dust with and without added chrysotile in comparison to crocidolite asbestos following short-term inhalation: Interim results

Chrysotile has been frequently used in the past in manufacturing brakes and continues to be used in brakes in many countries. This study was designed to provide an understanding of the biokinetics and potential toxicology following inhalation of brake dust following short term exposure in rats. The deposition, translocation and pathological response of brake dust derived from brake pads manufactured with chrysotile were evaluated in comparison to the amphibole, crocidolite asbestos. Rats were exposed by inhalation 6 h/day for 5 days to either brake dust obtained by sanding of brake-drums manufactured with chrysotile, a mixture of chrysotile and the brake dust or crocidolite asbestos. No significant pathological response was observed at any time point in either the brake dust or chrysotile/brake dust exposure groups. The long chrysotile fibers (> 20 μm) cleared quickly with T_1/2 estimated as 30 and 33 days, respectively in the brake dust and the chrysotile/brake dust exposure groups. In contrast, the long crocidolite fibers had a T_1/2 > 1000 days and initiated a rapid inflammatory response in the lung following exposure resulting in a 5-fold increase in fibrotic response within 91 days. These results provide support that brake dust derived from chrysotile containing brake drums would not initiate a pathological response in the lung following short term inhalation.     

Evaluation of driving skills after anterior cruciate ligament reconstruction with hamstring autograft

Background

There are no well-established guidelines for safe driving after injury or surgical treatment. The purpose of this study was to assess the aptitude to regain driving skills and brake reaction abilities after anterior cruciate ligament (ACL) surgery.

Evaluation of exposure to the airborne asbestos in an automobile brake and clutch manufacturing industry in Iran

About 2000 tons of chrysotile is used annually to produce friction materials in Islamic Republic of Iran. Approximately, 3000 workers are exposed to the asbestos fibers in the different processes of brake and clutch manufacturing. In the current study, asbestos fiber concentrations during brake and clutch manufacture were measured. This study also evaluated the fiber size and morphology distribution according to the Asbestos International Association (AIA) for standardization analytical method for asbestos.     

芳砜纶增强的新型摩擦材料研究

研究了芳砜纶纤维增强新型摩擦材料。采用分步干式开松法解决了芳砜纶的散问题，应用正交设计法优化芳砜纶磨擦材料的配方。研究表明该摩擦材料性能优于半金属摩擦材料和石棉摩擦材料。     

Standardizing the RT-2S Brake Reaction Time Tester

The purpose of the study was to standardize the RT-2S brake reaction time tester as an alternative brake reaction timer to the American Automobile Association's (AAA) blue box that is no longer manufactured. Three hundred ninety-six subjects across the lifespan participated by using the RT-2S in a standard manner. Results were analyzed using the age groups used by AAA. Results indicated that male reaction times are faster, and as age increases, reaction times decrease. Although the RT-2S reaction times were slower than the norms for AAA, results suggest that the RT-2S is a reliable and valid tool for measuring simple brake reaction time.     

综合康复治疗对膝关节骨折术后功能恢复的疗效观察

目的观察膝关节周围骨折术后综合康复治疗的效果。方法将沈阳市骨科医院于2010年3月至2012年3月收治的90例膝关节周围骨折患者随机分为治疗组和对照组,各45例,治疗组采用术后实施心理疏导、物理因子治疗、牵伸技术、关节松功术、肌力训练等一系列综合康复治疗措施,对照组采用骨科常规处理,患者自主锻炼治疗。所有患者均行美国特种外科医院膝关节评分和膝关节活动范围测量。结果两组治疗前后关节活动度比较,均有较大提高,治疗组较对照组改善更显著,比较差异均有统计学意义(P<0.05);治疗组优良率显著高于对照组(P<0.01)。结论综合康复治疗可显著提高膝关节活动范围,恢复膝关节的功能。     

Brake reaction time before and after surgery for patients with sequestrectomy versus conventional microdiscectomy

The aim of this study was to compare the effects of sequestrectomy versus conventional microdiscectomy on breaking response time (BRT) for lumbar disc herniation (LDH). BRT is the key factor for return to drive recommendations after surgery.A prospective clinical study was conducted. Patients aged 25–65 years who underwent surgery for lumbar disc herniation and held a valid motorcar driving license were recruited in a single institution. The patients were assessed before surgery, immediately after the surgery and at the follow up examination 30 days post-surgery. BRT was measured using a driving simulator, a visual analogue scale (VAS) was used for pain assessment. BRT values were compared with BRT values of a healthy control group.In patients treated with microdiscectomy BRT reduced from 749 (±223) msec before surgery to 649 (±223) msec immediately after the surgery. In the sequestrectomy group BRT reduced from 852 (±561) msec before surgery to 693 (±173) msec immediately after the surgery. BRT at follow up was 610 (±145) msec for patients treated with microdiscectomy and 630 (±98) msec for patients operated with sequestrectomy. BRT for healthy controls was 487 (±116) msec. Pain improved significantly for both patient samples.Sequestrectomy and microdiscectomy were associated with similar effects on pain and BRT after surgery. There was no statistically significant difference between BRT of both patient samples at 30 days follow up examination. Both surgical techniques showed a positive effect on BRT. No statistically significant difference between sequestrectomy and microdiscectomy on BRT could be found.