THOOTHUKUDI: A research study has found presence of microplastics in the salt manufactured in Thoothukudi district.
The food safety officials concerned have assured they will look into the microplastic contamination seriously as periodic sample tests had also revealed the presence of extraneous matters.
Thoothukudi is the second-largest producer of salt in the country next to Gujarat, with an average estimated production of 25 lakh tonnes of salt every year. Roughly 25,000 acres of land along the coastline are brought under salt pans which employ at least 30000 labourers, with a majority being women.
The salt manufacturing process in Thoothukudi involves pumping of saline groundwater into evaporation pans which are left to crystallise under direct sunlight in strictly monitored conditions so as to obtain fine quality of sodium chloride.
Exposure of the seawater to wind without moisture and strong sunlight quickens the formation of salt crystals by increasing the evaporation rate. The salt collected from the pan is processed with the addition of iodine and also refined to achieve free-flowing texture before being packed.
The research conducted by six geologists including a foreigner Sang Yong Chung of South Korea, has been published in Elsevier's Marine Pollution Bulletin.
The researchers had collected 25 samples from different salt pans between Vembar and Tiruchendur along coastal areas. The microplastics were extracted by several methods underscored in many studies including atomic force microscopy (AFM). The presence of microplastic particles was confirmed by a micro-Fourier transform infrared spectrometer, the researchers said.
The lead author of the study S Selvam, assistant professor in VOC College, Thoothukudi told TNIE that the study had revealed the presence of microplastics such as nylon, cellulose, polyethylene and polypropylene, and some non-plastic particles in the salt. The microplastics measuring less than 100m formed the major part of the salts, accounting to 60 percent of the microplastics among the total pollutants, he said.
Selvam also observed higher levels of microplastic waste in the salt samples collected at a bridge near the Thoothukudi thermal power plant, Muthaiyapuram, near Roach park, near SPIC area, near heavy water plant area and at Mullakadu, incidentally these areas are in the periphery of Thoothukudi corporation. The domestic waste materials were found to be the main source of polyethylene and polypropylene contaminants, he said.
Selvam added that this is a baseline study since there is no previous research in the microplastic contamination of salts. The researchers could not compare the level of contaminations over the years, due to the lack of previous studies on the salt pan in Thoothukudi, he said. However, the researchers had managed to compare the polymer type of microplastic contamination with the sea salt manufactured in China and Spain, he said.
Accordingly, the total contamination of the Thoothukudi salt constitutes 41.5 percent of polyethylene, which was 12.5 percent in the salt manufactured in China and 3.3 percent in Spain. While the presence of polypropylene in Thoothukudi salt was 22.7 percent, it was 18.8 percent in China and 6.7 percent in Spain. The contaminations of cellulose and nylon respectively constituted11.2 percent and 8.7 percent in Thoothukudi salt, which was nil in China and Spain. Similarly, the presence of unidentified particles was 11.2 percent in Thoothukudi salt as against 3.8 percent in China and 1.2 percent in Spain, the comparative analysis reveals.
The researchers attributed the plastic pollution around the salt pans to improper disposal of polyethylene products in the form of tea cups, milk packet covers, medicine wrappers and plastics along the seashore. Nylon has been a chief pollutant along coastline due to discarded fish nets and nylon ropes. Whereas, the cellulose sponge clothes waste was derived from textile industries around the salt pan stations, they said.
Selvam reiterated that the main objective of the study is to highlight the microplastic contamination in salts produced in Thoothukudi salt pans, as such detailed studies on the presence of microplastic salt and its impact over human health lacks in India, Selvam added.
As minimum presence of microplastics in the edible salts could pose a threat to human health through food consumption, the researchers had recommended controlling littering plastics around salt pan areas, particularly in the periphery of urban Thoothukudi which is a major salt producer region.
When asked, officials attached to the food safety and drug administration said that no laboratory tests on salt samples had reported micro plastic contaminations before. The 229 samples lifted between the fiscal 2013-14 and 2020-21, had reported 62 samples as substandard and mis-branded, while three samples as unsafe for consumption due to high presence of insoluble matters.
According to Food Safety designated officer Dr Mariappan, the extraneous matters are the insoluble substances, which are allowed to an extent of one percent of its dry weight, as per FSSAI Act. An edible salt must contain 96 percent of Sodium Chloride (NaCL), with moisture content not exceeding 6 percent and iodine not less than 15 ppm, besides the presence of insoluble matters are permitted for one percent, he said. "We will take random samples to rule out the presence of micro plastics and ensure hygienic practice", he said.
Meanwhile, the salt producers argue that they don't use seawater directly even as the authors affirm with the fact that the microplastics are present in the salt manufactured using bore water along the coastline.
Denying the presence of microplastics, a manager of a private salt processing unit which converts crystal salt into free flow salt, told TNIE that they find only an increased amount of sand particles in the raw salts during period lab tests. These sand particles accumulate in salt pans due to continuous rainfalls, he opined.
A co-author of the research article C Singaraja, assistant professor in Presidency college, Chennai, told TNIE that the plastic wastes reaches the sea (Gulf of Mannar) through various ways in Thoothukudi, with the main source being the Puckle canal that merges with the sea at Trespuram. Since the salt finds use in food every day, the authorities should increase deployments of experts such as geologists and hydrologists to observe the factors affecting the seawater quality, and increase random sample testing, so that the microplastic contaminations could be controlled, he said.