Natural fertilizers are not safer. Organic products tend to have higher levels of pathogens, such as E. coli, with the potential to make many people very ill. A study published in the Journal of Food Protection looked at 605 produce samples and found E. coli in 10% of the produce from organic farms, but only 2% of the produce of conventional farms.
A different study found Salmonella only on organic farms, and not on conventional farms. This is due to the use of manure, instead of artificial fertilizers. Conventional farms use manure as well, but they also use anti-microbial agents. Without those agents, organic foods run a high risk of containing bacteria that will make a person sick.