The use of a safety factor in setting health based permissible levels for occupational exposure

Summary When adequate human observations are not or scarcely available, permissible levels for occupational exposure have to be extrapolated from animal experiments. Taking into account experimental conditions, e. g., duration of exposure ( 3 months), animal species, knowledge of no- (adverse-) effect level or minim al-(adverse-) level, presence of data on human observations, the authors worked out a procedure for extrapolation. This procedure should only be applied for systemic non-carcinogenic effects. The proposed procedure is to be regarded as tentative and as suggestion for international discussion.The evaluation starts with a safety factor = 10 for extrapolation from dose/kg b. w. in long-term animal experiments to exposure of adult workers (40 h/wk); this factor corresponds to a safety factor = 3–10 for extrapolation from doses presented as concentrations in air. If long-term experimental exposure is 24 h daily, the safety factor can be lowered to the minimum value of 1. If only short-term exposure studies are available, the safety factor may have to be increased to a maximum of 400.     

人工耳蜗植入后不同言语处理器编程方案的比较

目的　了解和认识体佩式 (SPrint)和耳背式言语处理器 (ESPrit 3G)在调试中的不同特点 ,以便更好地进行人工耳蜗调式。方法　对 9例年龄 2～ 5 4岁的全聋患者于手术后 6～ 2 4个月由使用SPrint转换使用ESPrit 3G ,比较使用不同言语处理器调试所创建的电听力图之阈值 (thresholdlevel,T -L)和舒适阈 (comfortablelevel,C -L)、以及在ESPrit 3G使用不同程序时的声场测试和问卷调查结果 ,并进行统计学分析。结果　使用由SPrint获得的程序佩戴ESPrit 3G ,4例患者 (1组 )感觉聆听效果满意 ,与以往佩戴SPrint无差异。有 5例患者 (2组 )从不同言语处理器所获得的T -L和C -L有显著差异 (P <0 .0 1) ;使用不同的编程佩戴ESPrit3G进行声场 (啭音 )听阈测试 ,结果有显著差异 (P <0 .0 1) ;问卷调查显示使用经ESPrit3G直接调试获得的程序较使用由SPrint转换而来的程序有更好的聆听效果。 1组与使用ESPrit 3G调试获得程序的 2组的声场测试结果无差异 (P >0 .0 5 )。 1组与使用由SPrint转换而来程序的 2组的声场测试结果有显著差异 (P <0 .0 1)。结论　由佩戴SPrint转为使用ESPrit3G时 ,部分患者直接使用由SPrint转化而来的程序可能存在音量感受不足的情况 ,因此为了使患者获得更好的聆听效果 ,应经ESPrit 3G重新进行     

手工搬举作业的最大可接受搬举重量

目的对手工搬举作业的最大可接受搬举重量（MAWL）进行研究,为我国制订手工搬举作业劳动负荷的标准提供依据.方法 用心理物理学方法对13名男性和10名女性受试者的MAWL进行了研究,并与推荐搬举重量限值进行比较.结果 男女受试者的MAWL均随着搬举高度的上升逐渐降低.当搬举高度超过肩关节时,MAWL急剧下降.男性受试者在水平距离25 cm处,其推荐搬举重量均大于MAWL,但在水平距离45、63cm处,推荐值均小于MAWL.男性受试者的平均MAWL比女性受试者高30.8%.在同一高度,随着水平距离的增加,MAWL逐渐下降,男女受试者结果一致.男性受试者不对称搬举时,扭转的角度越大,MAWL越低.扭转角度和搬举能力呈负相关（r=-0.996 6,P＜0.01）.不同扭转角度的推荐搬举重量限值均比MAWL低,且差异有统计学意义（P＜0.01）.结论 美国国家职业安全卫生研究所（NIOSH）搬举方程对于水平距离和不对称的校正是充分的,但对于高度的校正是不足的,尤其是对于过肩的搬举作业是不适合的,对于过肩搬举作业的推荐搬举重量限值还应降低.NIOSH搬举方程应考虑性别因素的影响,可加入性别常数项S;如果性别为男性,则S=1;如果性别为女性,则S=0.692.     

基于数字乳腺图像分割算法的比较研究

乳腺疾病的发病率近年来不断增高,为增加诊断乳腺疾病的正确率和减轻医生的诊断负担,计算机辅助诊断技术应运而生。本文主要介绍运用阈值法和边缘检测法分割数字乳腺图像,实现对乳腺钙化点边缘的检测。     

正骨胶囊对小鼠消炎镇痛作用的实验研究

目的:观察正骨胶囊的消炎镇痛作用。方法:将经过筛选的60只雌性KM小鼠随机分为空白对照组,正骨胶囊高、中、低剂量组和云南白药组,每组12只,分别给予蒸馏水,3.45 g.mL-1正骨胶囊水溶液、1.72 g.mL-1正骨胶囊水溶液、0.86 g.mL-1正骨胶囊水溶液、0.37 g.mL-1云南白药水溶液按每10 g体重0.2 mL灌胃,并分别于给药前和末次给药后30 min测各鼠痛阈值。另取KM小鼠60只,随机分为空白组,正骨胶囊高、中、低剂量组和云南白药组,每组12只,分别给予蒸馏水、3.45 g.mL-1正骨胶囊水溶液、1.72 g.mL-1正骨胶囊水溶液、0.86 g.mL-1正骨胶囊水溶液、0.37 g.mL-1云南白药水溶液灌胃。测定其耳肿胀度和血清中白介素-1含量。结果:①给药后各组痛阈值比较,差异有统计学意义(F=3.989,P=0.006)。组间两两比较:云南白药组与空白组(q=4.03,P=0.007)、正骨胶囊高剂量组与空白组比较(q=3.47,P=0.046),差异有统计学意义;正骨胶囊中、低剂量组与空白组、云南白药组与正骨胶囊各剂量组及正骨胶囊各剂量组之间比较,差异均无统计学意义(P0.05)。②给药后各组小鼠耳肿胀度比较,差异有统计学意义(F=5.683,P=0.002)。组间两两比较:云南白药组与空白组(q=2.88,P=0.047)、正骨胶囊高剂量组与空白组比较(q=3.45,P=0.049),差异有统计学意义;正骨胶囊中、低剂量组与空白组、云南白药组与正骨胶囊各剂量组、正骨胶囊各剂量组之间比较,差异均无统计学意义(P0.05)。③给药后各组小鼠白介素-1值比较,差异有统计学意义(F=5.549,P=0.004)。组间两两比较:云南白药组与空白组(q=3.52,P=0.043)、正骨胶囊高剂量组与空白组(q=5.46,P=0.006)、正骨胶囊中剂量组与空白组(q=5.07,P=0.008)、正骨胶囊低剂量组与空白组比较(q=4.48,P=0.037),差异有统计学意义;云南白药组与正骨胶囊各剂量组、正骨胶囊各剂量组之间比较,差异均无统计学意义(P0.05)。结论:正骨胶囊能抑制白介素-1释放,有较好的抗炎作用,其效果与云南白药相当,剂量对其抗炎作用无明显影响;正骨胶囊在提高痛阈,改善耳肿胀度方面可能有效。     

Cocaine self-administration on a hold-down schedule of reinforcement in rats

Rationale and objective  Although many contingencies operating in the natural environment include continuous dimensions of responses and reinforcers, previous studies of drug self-administration have almost exclusively used discrete dimensions of responses (e.g., a lever press) and reinforcers (e.g., 1.0 mg/kg/injection cocaine). Therefore, the present study provides an initial examination under experimental conditions with both responses and reinforcers measured along continuous dimensions. Materials and methods  Cocaine-maintained responding was studied in rats under a novel, hold-down schedule of reinforcement wherein the duration of the response was directly related to the magnitude of the reinforcer. These conditions were established by activating the syringe pump when the lever was pressed down and turning the pump off when the lever was released. The concentration of cocaine available in the syringe was varied across sessions. Results  Cocaine self-administration was readily maintained under these conditions and remained stable across sessions. Responding was concentration dependent, with the number of responses and total duration of the response inversely related to concentration, and overall session intake of cocaine was stable across concentrations. In general, the duration of the responses were less than 0.5 s and did not vary as a function of concentration. Conclusions  Stability of responding under these schedule conditions was acquired quickly. This schedule of reinforcement may be useful for comparing across drug classes, can be extended for use with other types of responses and reinforcers, and may be more representative of the natural world where response-reinforcer contingencies are more likely to be experienced along continuous, rather than discrete, dimensions. Drake Morgan and Yu Liu contributed equally to this publication.     

老年人的颅顶慢电位阈值

应用测定颅顶慢电位(SVP)阈值的方法,研究了23～80岁健康人总计39人70耳的客观听力。结果表明听觉系统的老化在40岁即已开始,50岁后比较明显,并随年龄的增长而愈加明显。     

食管癌调强放疗靶区与肺体积比和处方剂量的关系

目的 研究食管癌调强放射治疗中能够做出既定目标的放疗计划时,靶区体积与肺体积比值和处方剂量的关系,从而帮助临床医生根据靶区情况,选择适合的处方剂量.方法 随机选取临床上己进行放射治疗的食管癌患者80例;其中病变范围包括全部食管癌类型,靶区根据ICRU(International Commission Radiologi...     

Threshold and non-threshold chemical carcinogens: A survey of the present regulatory landscape

For the proper regulation of a carcinogenic material it is necessary to fully understand its mode of action, and in particular whether it demonstrates a threshold of effect. This paper explores our present understanding of carcinogenicity and the mechanisms underlying the carcinogenic response. The concepts of genotoxic and non-genotoxic and threshold and non-threshold carcinogens are fully described. We provide summary tables of the types of cancer considered to be associated with exposure to a number of carcinogens and the available evidence relating to whether carcinogenicity occurs through a threshold or non-threshold mechanism. In light of these observations we consider how different regulatory bodies approach the question of chemical carcinogenesis, looking in particular at the definitions and methodologies used to derive Occupational Exposure Levels (OELs) for carcinogens. We conclude that unless proper differentiation is made between threshold and non-threshold carcinogens, inappropriate risk management measures may be put in place - and lead also to difficulties in translating carcinogenicity research findings into appropriate health policies. We recommend that clear differentiation between threshold and non-threshold carcinogens should be made by all expert groups and regulatory bodies dealing with carcinogen classification and risk assessment.     

不同背景波脑电图大鼠戊四氮致痫域值的探讨

目的 通过脑电图定量分析及戊四氮(PTZ)致痫观察,探讨不同背景波脑电图大鼠PTZ的致痫域值.方法 健康成年大鼠30只,采用头皮和皮层电极两种方法进行脑电图定量分析比较；建立大鼠急性脑外伤模型,采用头皮电极分别描记急性脑外伤组和对照组大鼠脑电图,并对各波段进行定量分析；探讨PTZ最小致痫量.结果 大鼠皮层脑电图的波形基本上与头皮导联的波形相似,但波幅较大,二者各波段的相对功率值比较差异无统计学意义(P＞0.05)；大鼠脑损伤组定量脑电图慢波(δ、θ波段)较健康大鼠对照组显著增加,快波α波显著减少,α、β、θ波相对功率值比较差异有统计学意义(P＜0.05)；大鼠脑损伤组致痫所需最小PTZ量值较对照组值要小(P＜0.05).结论 脑电图应用于临床非精确定位时,头皮导联可代替皮层导联；脑外伤后大鼠脑电图定量分析δ、θ慢波波段相对功率值明显增加,α、β快波波段相对功率值下降,其中α波减少更为显著；脑外伤后大鼠PTZ致痫域值下降.