Study design observational

Study design Observational, experimental, correlational, or descriptive Pilot study or full project... 

Soil lead concentrations have been observed to be associated with children s blood lead concentrations using multiple study designs - cross-sectional, ecological spatial, ecological temporal, prospective soil removal and isotopic (Laidlaw Filippelli, 2008). 

In a study designed to gather pharmacokinetic data, two healthy human volunteers were exposed to HFC-134a at 4,000 ppm delivered via a mouthpiece (Vinegar et al. 1997). The exposures were scheduled to last for 30 min. Blood samples were collected throughout the exposures. The exposures were abruptly terminated following an unexpected and uncontrollable rise in pulse rate in one subject and a drop in pulse rate and blood pressure and loss of consciousness in the second. This vasovagal response is sometimes observed... 

Two additional rat studies designed to investigate the reproductive effects of di-w-octylphthalatc exposure provide another observation on the hepatic effects of di-w-octylphthalate. Contrary to what is observed with di(2-ethylhexyl)phthalate, the concentration in liver of the essential element zinc was found not to be significantly reduced after 4 days of gavage exposure to 2,800 mg/kg/day of di-w-octylphthalatc (Foster et al. 1980), or 7 days of dietary exposure to 1,000 mg/kg/day of di-w-octylphthalate (Oishi and Hiraga 1980). 

Initial studies designed to obtain a valid subcellular fractionation scheme for rainbow trout liver illustrated the aryl-hydrocarbon (benzo[a]pyrene] hydroxylase activity separated with glucose-6-phosphatase (35). This observation indicated that the trout hemoprotein P-450-mediated monooxygenation system was located within the endoplasmic reticulum (microsomal fraction). 

Reductive dechlorination of penclomedine was, indeed, observed with liver microsomes under anaerobic conditions, indicating that a composite sequence such as this should not be dismissed without the benefit of further investigations. Given that the dehalogenation reactions exemplified by tri-fluridine and penclomedine may be less uncommon than implied here, mechanistic studies designed to clarify these processes would be most welcome. 

So, after associations are found, epidemiologists need to double check their study design and findings to reach for sources of bias, and must do everything possible to analyze any such bias to determine whether it could have a significant effect on the observed association. Then, confounders need to be similarly evalnated. 

Discussion This was the first study involving volunteers - four members of the laboratory staff who, with minimal baselines, were observed for 48 hours, or until effects appeared to have subsided. No statistical analysis was done with the data, due to the small sample size and the fact that this was essentially a range-finding study, designed to indicate the approximate doses required to produce moderate to severe incapacitation. 

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