Speed of light less uncertain than the previously accepted value. The remaining uncertainty was mainly related to the definition of the metre. As similar experiments found comparable results for "c", the 15th General Conference on Weights and Measures in 1975 recommended using the value for the speed of light. In 1983 the 17th CGPM found that wavelengths from frequency measurements and a given value for the speed of light are more reproducible than the previous standard. They kept the 1967 definition of second, so the caesium hyperfine frequency would now determine both the second and the metre. To do this, they redefined the
Hazard symbol carry a significant health risk (biohazards), including viral samples and used hypodermic needles (see sharps waste). The biohazard symbol was developed by the Dow Chemical Company in 1966 for their containment products. According to Charles Baldwin, an environmental-health engineer who contributed to its development: "We wanted something that was memorable but meaningless, so we could educate people as to what it means." In an article in "Science" in 1967, the symbol was presented as the new standard for all biological hazards ("biohazards"). The article explained that over 40 symbols were drawn up by Dow artists, and all of the symbols