Single exposure

Acute oral exposure, single dose No deaths Some deaths Persistent residues Tissue residues at death Brain Liver... 

Single exposure Multiple exposure Single exposure Multiple exposure... 

All of the previously mentioned exposure methods can be used to estimate either chronic exposure (over a period of years) or acute exposure (single day) for the United States population and population subgroups. Both chronic and acute assessments are usually based on a no observed adverse effect level (NOAEL) in an animal species. Acute exposure is defined relative to an acute (single dose) toxicological endpoint (usually a NOAEL) and may be expressed as a margin of exposure (MOE) or as a percentage of an acute reference dose that is based on a NOAEL and an uncertainty factor (see below). 

According to the ICH Harmonized Tripartite Guideline, particularly in cases of low or no toxicity, but also in cases of chronic exposure, single and two study designs in rodents are also possible and acceptable. 

Aggregate exposure (single pesticide) The combined exposure of a target to a single pesticide via all relevant pathways and sources (Norman, Ch. 10). 

Kind of exposure Single radiation dose Average radiation dose per capitem of the population... 

Acute Exposure single, short-term exposure. 

Worsening or complete relapse of melasma lesions from one episode of UV exposure single exposure to UV radiation increases size of melanocytes and increases tyrosinase activity [16]. 

Acute exposure Single exposure or several short-term exposures to a toxic substance. ... 

In a case-control study in 543 lung transplant recipients, 17 (3.1%) developed squamous cell carcinomas Mer a median follow-up of 36 months [62 ]. The median time to development was 19 months after transplantation. Risk factors by univariate analysis included older age, residence in locations with high levels of sun exposure, single-lung transplantation, and duration and cumulative dose of voriconazole. The duration of voriconazole therapy and residence in locations with high sun exposure were independent risk factors by multivariate analysis. The lesions were located on the head and neck in 94% of cases and 53% had multiple lesions. After surgery at least one further independent lesion developed in 47% of patients. There was local spread and distant metastases in 7% of cases. There were no deaths. 

Many different cancers are caused by exposures single chemicals and many different compounds are known to induce some cancers. Some compounds are known to cause more than one cancer type. It is not the purpose of this book to exhaustively explore the hundreds of known single chemical carcinogens and the cancers they induce. The following, however, are some illustrative examples of these. 

The dose rates shown in both Figures B-1 and B-2 are for a single pin. Dose rates from even a near full exposure single pin decay to le.ss than 100 rem/hr at the 3-ft dose point after only about three years. If the pins are left in a complete assembly, the 100-rem/hr level is reached at considerably longer decay times. Photon transport... 

Clearance of foreign materials (particles) from the lung and airways depends on the function of macrophages, ciliated cells and secretory cells, and on the physical and chemical properties of the alveolar cells. All these are affected by ozone exposure. Single acute exposure of animals and humans to ozone concentrations less than 0.6 ppm have been shown to accelerate clearance of particles from the tracheobronchial tree whereas acute exposures to ozone levels greater than 0.6 ppm caused a delay in particles clearance [79, 261]. Repeated exposures (2 h daily for 14 days) to 0.1 ppm ozone gave rise to acceleration in alveolar clearance of latex particles but had no effect on tracheobronchial clearance. These results, related to morphological studies, are consistent with certain adaptation [278-283]. 

---