Toxic mercury is received into the body through dental fillings, fish consumption, and PVC water pipes, plastic ,etc. They are largely made from a mercury-based process, making the vinyl industry one of the largest users of mercury.
Although there is a cover-up, there is enough research to connect the dots. For example, notice some associated links between neurological problems and mercury. I believe the real truth is so many times greater:
“The detailed reasons for the increased risk of PD [Parkinson’s Disease] in the amalgam filling cohort are still unknown; however, the elemental mercury (Hg) in dental amalgam might play an important role…High levels of MeHg [methylmercury] in the CNS, resulting in oxidative stress, have been found to be a major factor in neurological diseases [Nabi S. Toxic Effect of Mercury. Springer India; 2014.]…MeHg is posited as an important neurotoxicant…The patients exposed to dental amalgam filling were 1.583 times more likely to develop PD afterward compared to their non-exposed counterparts…” (Association between History of Dental Amalgam Fillings and Risk of Parkinson’s Disease: A Population-Based Retrospective Cohort Study in Taiwan)
“Sun et al.  evaluated the association between dental amalgam fillings and Alzheimer’s disease (AD) in a large scale Taiwanese population aged 65 years and older in a cross-sectional study and concluded that women’s exposure to amalgam was significantly associated with AD…” (Association between dental amalgam fillings and Alzheimer’s disease; Published online 2016 Jan 18)
“An average filling contains an estimated 800 milligrams of amalgam, with the average middle-aged adult having 8 fillings. The average North American adult has 3.2 grams or mercury (8 fillings x 800 mg per filling x 50% of total amalgam is mercury) of potential mercury vapor to go into the lungs, blood, and brain from dental fillings alone -- an average of about three-millionths of a gram a day - this does not include the amount of mercury we take in from vaccinations and from our food!... Mercury in "Silver Fillings" Causing Multiple Sclerosis (MS) and Central Nervous System Disorders… A multi-million dollar U.S. Government study conducted between 1988 and 1994 could hold the key to producing epidemiological data linking dental fillings to a myriad of illnesses. This new information, comes straight from the National Institute of Health, the NHANES III Study (National Health and Nutritional Examination Survey), a study that according to the mission statement of National Center for Health Sciences "is to provide statistical information that will guide the actions and policies to improve health of the American people. As the Nation's principal health statistics agency, NCHS leads the way with accurate, relevant, and timely data." A recent statistical analysis of this data was done to see if there were any links to dental fillings and adverse health conditions. Their initial figures revealed that while 78% of the American public have dental fillings, 95% of the people with International Classification of Disease Codes 340-349: "Disorders of the Central Nervous System", which include MS, Epilepsy, Paralysis and Migraines, have dental fillings…”
(Mercola, Learn How Mercury Is Affecting You and the Ones You Love)
I would watch what fish I consume, and evaluate mercury levels, remove mercury fillings (with a holistic dentist!), detox heavy metals, and avoid all plastic and PVC water pipes. This will be difficult, but some loved ones may be especially sensitive to mercury, lead, and other heavy metals found in plastic, PVC, CPVC, pesticides, etc.