Orders of magnitude (radiation) Orders of magnitude (radiation) Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning. Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1000 of a rem and 1 rem equals 0.01 Sv. Light radiation sickness begins at about 50–100 rad (0.5–1 gray (Gy), 0.5–1 Sv, 50–100 rem, 50,000–100,000 mrem). The following table includes some dosages for comparison purposes, using millisieverts (mSv) (one thousandth of
Samut Prakan radiation accident symbol. Although the symbol was displayed on the teletherapy head, none of those handling the device were aware of its meaning, nor were there written warnings in Thai. Together with the International Organization for Standardization (ISO), the IAEA developed a new symbol that would serve as an intuitive warning for large sources of ionizing radiation. The new symbol was published in 2007 as ISO 21482, and is intended to accompany the trefoil on internal components of devices containing dangerous sources to prevent persons from unknowingly disassembling them. In Thailand, however, substantial efforts to prevent further such occurrences had not materialized