Nuclear testing has been a concern for decades, with many countries having conducted tests in the past. According to recent data, North Korea was the most recent country to conduct a nuclear test in 2017. The Comprehensive Nuclear-Test-Ban Treaty (CTBT) organization's monitoring system recorded the test, which measured at least 140 kilotons, eight times more powerful than the bomb dropped on Hiroshima.

The use of nuclear bombs has had significant effects on human health and the environment. Studies have shown that radiation-related cancers and leukemia were expected to occur in the United States from nuclear testing-related fallout of the 1950s and 1960s. The Marshall Islands, where the US conducted tests, experienced displacement, loss of traditional lands, social stresses, and impoverishment.

The world's nine current nuclear states have approximately 13,000 nuclear warheads combined. While many countries have not tested their weapons in recent years, there is concern that resumption of testing could prompt other countries to follow suit. The CTBT organization continues to monitor nuclear tests worldwide, encouraging countries that haven't signed the treaty to disclose their testing.

Source: https://www.livescience.com/human-behavior/warfare/how-many-nuclear-bombs-have-been-used