Episodic exposure events

Estimating the risk to workers or the public from episodic events involving a one-time exposure to potentially harmful substances or activities... 

When spills and releases of hazardous gases or liquids occur, the concentration of the hazardous material in the vicinity of the release is often the greatest concern, since potential health effects on those nearby will be determined by the concentration of the substance at the time of the acute exposure. There are many models of routine continuous discharges (e.g., discharges arising from leaky valves in chemical plants), but these carmot be applied to single episodic events. Research on the ambient behavior of short-term environmental releases and the development of models for concentration profiles in episodic releases are cmcial if we are to plan appropriate safety and abatement measures. 

Factors associated with increased risk for recurrence in naturalistic studies of depressed children and adolescents may serve as guidance to the clinician to decide who needs maintenance treatment. These factors include history of prior depressive episodes, female sex, late onset, suicidality, double depression, subsyndromal symptoms, poor functioning, personality disorders, exposure to negative events (e.g., abuse, conflicts), and family history of recurrent MDD (<2 episodes) (Birmaher et ah, 1996 a,b Goodyer et ah, 1998 Fewin-sohn et ah, 1999 Rao et ah, 1999 Rueter et al., 1999 Weissman et ah, 1999a, b Klein et ah, 2001). 

Long-term AA-EQSs are intended to protect against long-term continuous exposure, and MAC-EQSs are intended to protect against short-term episodic events. It should be noted that the use of acute toxicity data for deriving AA-EQSs is considered permissible by some jurisdictions, for example, when suitable chronic toxicity data are not available (e.g., CCME, 2007), although the use of chronic data for this purpose is always preferable. 

Urban levels of air pollution (downtown Sao Paulo) modified the progression of urethane (3 g/ kg)-induced lung tumours in mice (Cury etal. 2000). Urban particles consist of three modes ul-trafine particles, accumulation mode particles (which together form the fine particle mode) and coarse mode particles. Ultrafine particles (those of <100nm diameter) contribute very little to the overall mass, but are very high in number, which in episodic events can reach several hundred thou-sand/cm in the urban air. The hypothesis that ultrafine particles are causally involved in adverse responses seen in sensitive humans is based on several studies summarised by OberdOrster (2001). Timblin etal. (2002) demonstrated the development of dose-related proliferation and apoptosis after exposure of an alveolar epithelial cell line (CIO) to particulate matter or to ultrafine carbon black, a component of particulate matter. Ribonuclease protection assays demonstrated that increases in mRNA levels of the early response protooncogenes c-jun, junB, fra-l, and/ra-2 accompanied cell pro-hferation at low concentrations of particulate matter whereas apoptotic concentrations of particulate... 

When an employee experiences the signs or symptoms of an injury or illness as a result of an event or exposure in the workplace, such as an episode of occupational asthma, must I treat the episode as a new case Yes, because the episode or recurrence was caused by an event... 

Yes. The incident must be treated as a new case because the episode or recurrence was caused by an event or exposure in the workplace. 

---