Some traditional cured meat (such as authentic Parma ham and some authentic Spanish chorizo and Italian salami) are cured with salt alone. Today, potassium nitrate and sodium nitrite (in conjunction with salt) are the most common agents in curing meat, because they bond to the myoglobin and act as a substitute for the oxygen, thus turning myoglobin red. More recent evidence shows that these chemicals also inhibit the growth of the bacteria that cause the disease botulism. Yet, a 2018 study by the British Meat Producers Association determined that legally permitted levels of nitrite have no effect on the growth of the "Clostridium botulinum" bacteria which causes botulism, which in line with the UK’s Advisory Committee on the Microbiological Safety of Food opinion that nitrites are not required to prevent "C. botulinum" growth and extend shelf life.