Knowledge is a conscious, intentional and individual act to learn object's qualities and is firstly referred to who knows but also to the object thing what is known. Its development has been close to human thought evolution. Epistemology, the science that studies knowledge, is based in scientific research that begins with a hypothesis exposition and develops afterwards with mathematical models to have verifiable and valid conclusions. Scientific research is an accepted and validated process for new facts or questions solutions guided to recognize principles and laws that sustain man's life in the world. It owns methods based on hypothesisdeduction/ induction complemented with statistics and calculation probabilities. Scientific researchers should know its theory and evolution because they are indispensable tools in research and its good handling will allow technical and suitable answers ...

Introduction: Work with lead is a universal industrial problem, especially when done without labor hygiene approach. Lead Peruvian’s mining and metallurgy maintains good quality programs for management of occupational health, but informal Peruvian industry does not. Objectives: To determine the actual heath status of handicraft and informal batteries factories workers using blood lead levels as exposition indicators. Design: Observational and transversal study. Setting: Ilo, Peru’s Occupational Health Service Hospital. Participants: Workers at four handicraft informal batteries factories. Interventions: Information was obtained from 41 workers by direct interview, from August 1999 through January 2000. For blood lead levels determination we used atomic absorption spectrophotometry with graphite oven, and for hemoglobin, microhematocrit. We obtained percentages, averages, ranges, and ...