By 
Manufacturers have widely used sodium benzoate as a preservative in fruit juice, carbonated drinks, pickles, etc
Sodium benzoate and its close relative benzoic acid, have been used steadily for centuries to prevent growth of microorganisms in acidic foods. They occur naturally in many plants and animals.
This food additive appears to be safe for most people, though it may cause hives, asthma, or other allergic reactions in sensitive individuals.
Carcinogen creation due to Sodium Benzoate, Benzoic Acid
A reaction occurs when sodium benzoate is used in beverages that also contain ascorbic acid (vitamin C).
The two substances, in an acidic solution, can react together in the presence of light to form small amounts of benzene, a chemical that causes leukemia and other cancers. Though the amounts of benzene that forms is really small, leading to only a very small risk of cancer, the risk can be real.
In the early 1990s the FDA had urged companies not to use benzoate in products that also contain ascorbic acid, but in the 2000s companies were still using that combination. A lawsuit filed in 2006 by private attorneys ultimately forced Coca-Cola, PepsiCo, and other soft-drink makers in the U.S. to reformulate affected beverages, typically fruit-flavored products.
In India, some manufacturers like Patanjali currently use sodium benzoate as a preservative in particularly vitamin C rich products like aawla (gooseberry) juice. We think that this is irresponsible as the bottles are not opaque and frequently exposed to light in shop shelves.
Cancer chemical found in drinks in Britain
The British food standards agency watchdog conducted tests on 230 different products which revealed levels of up to eight parts per billion in some soft drinks.
The legal limit of one part per billion on the amount of benzene is allowed in drinking water, but there are no UK restrictions on the amount of the chemical permitted in soft drinks.
The soft drinks industry has known for 15 years that the preservative sodium benzoate can produce benzene if mixed with ascorbic acid or commonly known as Vitamin C.
Benzene has been linked to leukaemia and other cancers of the blood and is also found in pollutants such as car exhaust fumes.
Dozens of soft drink brands contain both sodium benzoate and ascorbic acid, which can create benzene if mixed, but the British Soft Drinks Association insists the levels produced pose no risk to health.
Sources:
Hi,
I was surfing the net, researching on the side-effects of sodium Benzoate in combination with vitamin C (especially pertaining to amla juice). I came across several articles that mention that the solution containing vitamin c and sodium benzoate will form benzene only when its ph is lower than 7 – additionally the levels of benzene formed is almost negligible between ph levels 3 and 7. Even you have stated, “The two substances, in an acidic solution, can react together in the presence of light to form small amounts of benzene…” The thing is that amla is alkaline in nature, so amla juice must have ph more than 7. So, if I understand correctly, benzene cannot be formed in amla juice containing sodium benzoate.
P.S.: I am just speculating after spending a lot of time on the internet reading on this topic. Just wanted your views. I am curious because i was fascinated by the many health benefits of amla juice, and I really want to start consuming it, if it’s safe.