The Causes of Autism

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Study Links Triclosan in Household Products to Autism Spectrum Disorder

Who are the splendid authors, what is the title of the study, and what year was it published?

Authors: Qionghui Wu, Ting Yang, Li Chen, Ying Dai, Hua Wei, Feiyong Jia, Yan Hao, Ling Li, Jie Zhang, Lijie Wu, Xiaoyan Ke, Mingji Yi, Qi Hong, Jinjin Chen, Shuanfeng Fang, Yichao Wang, Qi Wang, Chunhua Jin, Ronggui Hu, Jie Chen, Tingyu Li.

Title: Early life exposure to triclosan from antimicrobial daily necessities may increase the potential risk of autism spectrum disorder: A multicenter study in China. Ecotoxicology and Environmental Safety 247 (2022) 114197

Year: 2022

What is the study about?

A research study investigated whether exposure to triclosan (TCS) from antimicrobial household products during pregnancy increased the risk of autism spectrum disorder (ASD) in offspring. Triclosan (TCS) is a widely used antimicrobial chemical found in numerous products, from soaps and cosmetics to medical equipment. Its presence in the environment and food chain has raised concerns about its impact on human health, particularly on nervous system development.

(Pexels)

What previous research is there on this topic?

Previous research has shown that maternal use of antibacterial products containing TCS results in higher TCS levels in both mothers and infants. Animal studies have suggested that TCS exposure can cause neuronal oxidative damage, affect neurodevelopmental processes, and induce neuroimmune abnormalities, leading to impaired cognition, decreased social performance, and behavioral problems in children. Moreover, a positive correlation has been observed between maternal use of antibacterial daily necessities and log-transformed values of TCS concentrations in offspring. These findings highlight the need for further research into the long-term effects of TCS exposure during pregnancy on neurodevelopmental outcomes in offspring.

Brief history, from Weatherly and Gosse (2017)

The production of triclosan (TCS) in the US increased from 0.5-1 million pounds per year in 1977 to 1-10 million pounds in 1998. Estimated global production of TCS in 2011 was 14 million pounds, with a decrease to 10.5 million pounds in 2015. TCS was found in 93% of liquid, gel, or foam soaps in the late 2000s and was included in consumer products worth $886 million in total sales. TCS-containing products were sold at a high rate between 2008 and 2009, resulting in annual consumption of 132 million liters.

Other Health Effects of Relevance to this Library [not exhaustive, see Weatherly and Gosse (2017) for more information]

Four studies between 2015 and 2016 found TCS affected mitochondrial function. A 2016 study found a reduction in hormone levels after oral gavage of TCS. Another study in 2015 found an association between spontaneous abortions and high TCS in urine, while a 2017 study found an association between TCS and birth defects. A 2014 study found Triclosan was associated with food sensitization, and this association was stronger among children with eczema.

While TCS was banned by the FDA in soap products in September 2016, it remains allowed in toothpaste, hand sanitizer, and mouthwash.

What methods were used?

Participants

This research study focused on children aged 2-7 years from 13 cities in China, including 1444 children with autism spectrum disorder (ASD) and typically developing (TD) children. Participants were recruited through voluntary participation and informed consent signed by their guardians, and those with congenital or genetic diseases that affect growth or development, history of other developmental disorders or mental illnesses, and those whose parents refused to sign informed consent were excluded from the study. During the investigation, 5 milliliters of venous blood was collected from the participants at the local hospital. The children’s guardians filled out the basic questionnaire, and professional developmental pediatricians evaluated the core symptoms of children with ASD.

(Pexels)

Autism Symptoms

Autism Behavior Checklist (ABC), Childhood Autism Rating Scale (CARS), and Social Response Scale (SRS) were used to evaluate the core symptoms of children with ASD. The Children Neuropsychological and Behavior Scale-Revision 2016 was also used to assess neurodevelopmental levels

Blood Sample

The blood sample is collected from the participants and treated with a method called liquid-liquid extraction, which separates the triclosan from other substances in the blood. An internal standard called TCS-d3 is added to the sample to help with analysis. The sample is then tested using a machine called Agilent 6470 Triple Quad LC-MS/MS system, which separates and measures the amount of triclosan in the sample. This process uses mobile phases and a chromatographic column to separate and identify the chemical.

What were the findings?

Maternal Use of Antibacterial Daily Necessities

The study found that maternal use of antibacterial daily necessities during pregnancy, containing triclosan (TCS), was positively associated with the risk of autism spectrum disorder (ASD) in offspring. Children whose mothers used these products during pregnancy scored higher on the ABC social self-help subscale.

Male vs. Female Differences

In a sex-stratified analysis, the use of antibacterial products during pregnancy was positively associated with the ABC social self-help subscale score in male offspring. However, no statistical differences were found among female children.

Triclosan

Maternal use of antibacterial daily necessities was also positively associated with log-transformed values of TCS concentrations in offspring, with higher median levels of serum TCS found in children whose mothers used these products. This suggests that maternal use of antibacterial daily necessities during pregnancy may be a potential risk factor for ASD in offspring.

TCS and Autism Symptoms

The study found that higher levels of TCS were positively associated with the severity of autism core symptoms, such as social cognition, social communication, social motivation, and autism behavior mannerisms, in male children with ASD. However, there was no association between TCS levels and CNBS-R2016 scores in both boys and girls. When TCS levels were divided into four quartiles, children in the fourth quartile had higher scale scores in ABC self-help subscale, SRS social cognition subscale, SRS social communication subscale, SRS social motivation subscale, SRS autism behavior mannerisms subscale, and CARS, suggesting that children with higher TCS levels have more severe core symptoms of ASD.

(Pixabay)

TCS, Autism Symptoms, and Sex Differences

The study found that in male children with ASD, TCS concentrations were positively associated with social cognition, social communication, social motivation, autism behavior mannerisms, and total SRS scores. However, there were no statistically significant differences among female children with ASD. Additionally, there was no association between TCS levels and CNBS-R2016 scores in either boys or girls. These findings suggest that the association between TCS levels and ASD core symptoms is more pronounced in male children than in female children.

What are implications of this study?

TCS is a commonly used broad-spectrum antibacterial agent found in daily necessities. Studies have shown that exposure to TCS in pregnant women can increase TCS levels in offspring. Chemical exposure in daily products within the same household has also been positively correlated in mothers and children. The higher level of TCS in offspring whose mothers used antibacterial daily necessities during pregnancy was likely due to exposure to TCS-containing commodities in the home environment. Maternal UADN may increase the risk of ASD in offspring through excessive exposure to TCS. TCS has been associated with behavioral problems in male children, suggesting a specific sex-dependent effect. TCS exposure may also have a regulatory effect on sex hormones.

What other research within the library is this study related to?

There are other studies which have found sex differences, including the one regarding aluminium in the brain, as well as the study about phthalate exposures.

What are the limitations of this study?

It was a retrospective study, and the researchers were therefore unable to obtain biological samples of mothers during pregnancy to investigate the TCS content in antibacterial daily necessities used during pregnancy. The frequency of maternal UADN during pregnancy was not explored. The sample size was restricted to only three cities in China, with a sample loss rate of less than 10%. The questionnaires only collected general information about the child and parents, and no detailed information about when the mother used UADN during pregnancy. Lastly, the study only included children aged 2-7 years, and no follow-up assessments of TCS exposure in different age groups were conducted.

Can I read the full study somewhere?

Yessum. Click on the link.

Shh. Quiet in the hall.

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