Study finds microplastics in bottled, loose soybean oil sold in Dhaka

Microplastics have been found in both bottled and loose soybean oil sold in Dhaka, with loose oil containing higher levels, a recent study has found. 

Researchers from Jahangirnagar University and Bangladesh University of Professionals (BUP) found an average of 53,922 particles per litre after analysing oil collected from the capital. Loose oil contained around 24% more particles than bottled oil.

The findings were recently published in the Journal of Food Composition and Analysis.

The study identified six types of plastic polymers in the oil samples: low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), polyethylene terephthalate (PETE), polyurethane (PU) and nylon.

The researchers said the entry of such tiny plastic particles into the human body through food could become a long-term concern.

The researchers collected 60 one-litre samples. Three brands of bottled oil were bought from supermarkets in Dhaka, while loose oil was collected from Tejgaon, Uttara and Dhaka Cantonment.

Ten samples from each of the six groups were mixed to create six combined samples. Each was tested three times using microscopes and laboratory methods that identify different types of plastic.

Loose oil contained an average of 59,778 particles per litre, compared with 48,067 in bottled oil.

The loose-oil sample from Tejgaon recorded the highest level, at 70,467 particles per litre.

The researchers said nearby plastic and textile factories, airborne fibres and repeated use of plastic containers may have contributed to the higher level in loose oil.

Bottled oil may also be contaminated during processing and packaging through contact with plastic pipes, seals, filters and containers, they said.

Plastics found in the oil

Fibres made up 82.5% of the particles found in the samples, while fragments accounted for 9.6%.

Transparent particles were the most common by colour, making up 56.29% of the total.

Particles measuring between 101 and 500 micrometres formed the largest size group at 35.84%. Those measuring between 501 and 1,000 micrometres accounted for 33.2%.

Using Fourier Transform Infrared Spectroscopy, the researchers identified six plastic polymers in the oil samples: LDPE, HDPE, PP, PETE, PU and nylon.

They gave particular attention to polyurethane and nylon. The researchers said this was, to their knowledge, the first report of the two polymers in soybean oil in Bangladesh.

Polyethylene and polypropylene are widely used in bottles, caps, seals and other packaging. Polyurethane is used in adhesives and coatings, while nylon is used in filters and meshes.

They suggested the particles may have entered the oil through processing equipment, seals or filters. 

Study co-author and Jahangirnagar University environmental sciences Professor Shafi M Tareq said, "We analysed both branded, or bottled, and non-branded, or loose, oil sold in Dhaka. Our analysis found an average of several thousand microplastic particles per litre, with fibres and fragments being the most common."

Estimated exposure higher for children

The researchers also estimated human exposure to microplastics based on daily soybean oil consumption and assumed body weights of 70kg for adults and 16kg for children.

Under the study's body-weight-adjusted model, estimated daily exposure was 17.65 particles for adults and 77.21 particles for children.

The annual estimates were 6,441 particles for adults and 28,180 for children. The study estimated a child's lifetime exposure at around 20.9 lakh particles.

These figures are modelled estimates based on assumed oil consumption, body weight and life expectancy. They are not measurements of microplastics detected inside people's bodies.

Citing earlier studies, the researchers said prolonged exposure to microplastics may be associated with gastrointestinal inflammation, hormonal disruption, metabolic problems and cellular damage.

They also said particles smaller than 130 micrometres may cross the gut lining and enter body tissues. However, the soybean oil study did not directly examine health effects in humans.

"Microplastics are now considered an emerging contaminant," Professor Tareq said.

"They may create long-term risks to human health, including hormonal imbalance, metabolic problems and adverse effects on the reproductive system."

The study classified all six sample groups as having moderate contamination under its microplastic contamination factor.

However, its overall pollution-load index placed the samples in the low pollution-risk category. The index indicates relative contamination and is not an official food-safety threshold.

Public health expert and medicine specialist Dr MH Choudhury Lelin told The Business Standard that microplastics pose a multidimensional threat to human health, noting that studies have detected them in the human brain, lungs, liver, kidneys, stomach, male testicles and female ovaries, as well as in everyday products such as toothpaste.

"There is a risk of microplastics entering the body through daily-use products. Harmful chemicals can attach to these particles, potentially increasing cancer risk and damaging the liver, kidneys and other vital organs," he said.

Monitoring gaps

The researchers said Bangladesh lacked specific rules and regular monitoring for microplastics in food.

As a result, little information is available on how much microplastic enters the food chain or its possible effects, they said.

They called for stronger checks throughout soybean oil processing and packaging, the use of food-grade filters and tighter control over the storage and sale of loose oil.

"Completely eliminating plastic is not realistic at present," Professor Tareq said.

"Alongside proper plastic-waste management, reuse and recycling systems must be improved."

The researchers said microplastics in edible oil were linked not only to product quality but also to food safety and public health.

They called for possible sources of contamination to be identified and reduced during production, refining, storage, transport and sale.

The authors also said the lack of more advanced testing equipment may have limited their ability to detect the smallest or less distinct particles.

Dr Lelin also said stronger quality control and stricter monitoring at all stages of production and processing are needed to reduce contamination.

He added that while microplastics are not a new problem, growing plastic pollution and increasing research have highlighted rising human exposure and its potential health risks.