Controlled exposure

X-rays find wide applications in X-ray photography and in crystallography. Prolonged exposure of the human body to the rays induces a dangerous form of dermatitis, and even sterility, but controlled exposures are applied to alleviate cancer. 

Clinical studies Experimental Controlled exposure Artificial exposure... 

Before starting any work which is liable to expose employees to asbestos dust, an assessment of the work is required to help decide the measures necessary to control exposure. This should ... 

Control exposures by engineering techniques, e.g. containment, shielding, ventilation (consider need for in-duct filters to remove contamination prior to exhausting to atmosphere), backed up by systems of work and personal protection including approved respirators where necessary. 

Major hazard aspects of the transport of dangerous substances 1991 Recommendations for training users of non-agricultural pesticides Health surveillance under COSHH. Guidance for employers Anaesthetic agents. Controlling exposure under COSHH Risk assessments of notified new substances... 

Relocating or rotating susceptible individuals Move susceptible individuals away from the area where they experience symptoms. Controlling exposure by relocating susceptible individuals may be the only practical approach in a limited number of cases, but it is probably the least desirable option and should be used only when all other strategies are ineffective in resolving complaints. 

The best way to control exposure is to replace dangerous agents with safer ones. Today, highly toxic solvents, such as benzene, bromobenzenc, carbon tetrachloride, and chloroform are no longer extensively used. Benzene remains, however, an important chemical in the petrochemical industry, but the processes where it is used are clc)sed. 

Most packaged foods require a barrier against gases, flavors, or odors to maintain product quality and provide acceptable shelf life. Baked foods usually need moisture protection, while fresh meats and vegetables require low or controlled exposure to oxygen... 

In choosing method(s) to control exposure, COSHH limits the use of personal protective equipment (e.g. respirators, dust masks, protective clothing) as the means of protection to those situations only where other measures cannot adequately control exposure. 

If for a carcinogen prevention of exposure is not reasonably practicable by using an alternative substance or process there is a requirement to apply all the measures fisted in Table 5.21. If these measures do not provide adequate control then suitable personal protective equipment as will adequately control exposure must be provided. 

Konietzko H, Elster I, Bengsath A. 1975a. [EEG variation with controlled exposure to trichloroethylene.] Int Arch Occup Environ Health 35 257-264. (German)... 

Historically, risk reduction strategies have been focused on the exposure side of the risk equation and in many cases have been very successful. However, there are inherent flaws in focusing primarily on controlling exposure that will be identified here. 

Article 3(37) of REACH defines exposure scenarios as the set of conditions, including operational conditions and risk management measures, that describe how the substance is manufactured or used during its life-cycle and how the manufacturer or importer controls, or recommends downstream users to control, exposures of humans and the environment [...] . 

In humans, metabolites of acrylonitrile have been identified in urine following occupational exposure (assumed to be by the inhalation route), and also in controlled exposure studies. Metabolites identified in humans were the same as those in animals (Jakubowski et al. 1987 Sakurai et al. 

The deterioration of the physical properties of rubber products when exposed to service conditions also the controlled exposure of rubber samples to a variety of deteriorating influences in the evaluation of antioxidants and antiozonants. See Accelerated Ageing. 

For vapour detection there are three aspects that are modelled sensitivity, response time, and regeneration. The sensitivity determines at which concentration level the detector will respond. The theoretical detector output (alarm or no alarm) is calculated by comparing the input data (concentration, relative humidity) with empirical detector display outputs, obtained during controlled exposure laboratory experiments. The response time determines how long it takes before the detector actually shows the response and it depends on the concentration level. The regeneration time determines how long it takes, after a positive detection, before the detector can do a new measurement. 

Female ability to control exposure to male scent at critical times may help to explain why similar pregnancy-blocking stimuli have produced conflicting results in different experiments. For example in one study manipulating male social status (Labov 1981a), females were housed directly below males, while a similar study (Huck 1982) housed females adjacent to males, separated by mesh. The pregnancy... 

Time (hours) before/after MP-conditioning or control exposure... 

Testing of the subjects consisted of both subjective evaluations and physiological and central nervous system responses observed under medical supervision. The lowest concentration at which odor was detected was 0.2 ppm (four of nine subjects), but the ability to detect the odor disappeared within 5 min. Subjective symptoms consisted of headache and eye irritation. At 0.1 ppm, two of the subjects experienced mild headache (Table 2-3). One of these subjects had developed headache during each of the control exposures and during the exposure at 0.03 ppm. The other subject developed headache after 6 h, and the headache continued for several hours postexposure. 

Barcroft (1931) described the controlled exposure of a 45-year-old, 70-kg man and a 12-kg dog to a concentration of HCN at 500-625 ppm in an airtight chamber. The human volunteer attempted to maintain the same level of activity as the dog. The dog became unsteady at 50 seconds (s), unconscious at 75 s, and convulsive at 90 s. One second later, the man walked out of the exposure chamber with no apparent effect. At 5 min after initiation of exposure, the man experienced a momentary feeling of nausea, and at 10 min from the... 

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