Hoá Chất Biosphenol A an toàn hay không? potx

Polycarbonate plastic possesses a unique balance of toughness, optical clarity, high heat resistance, and excellent electrical resistance and has many industrial uses including media pro

Hoá Chất Biosphenol A an toàn hay không?

Introduction

For the last 50 years, bisphenol A (BPA – CAS Nọ 80-05-7) is a

chemical used primarily to make polycarbonate plastic and epoxy resins

Polycarbonate plastic possesses a unique balance of toughness, optical

clarity, high heat resistance, and excellent electrical resistance and has many

industrial uses including media products (eg., CDs, DVDs), electronic

equipments, sport equipments, bicycle helmets, food containers, drink

containers, baby bottles, medical devices and many other products Epoxy

resins are commonly used to coat metal cans to protect the safety and

integrity of canned foods and beverages and also are used as dental sealants

Exposure to BPA

Human exposure to BPA is via the use of plastic containers, bottles,

food and beverage cans and dental sealants BPA has been found to leach

from bottle and can liners and migrates into foods and beverages

Researchers from government agencies, academia, and industry worldwide

have studied the migration potential of BPA from polycarbonate products

into foods and beverages These studies consistently show that the level of

BPA migrating into food is extremely low, generally less than 5 parts per

billion under conditions typical for uses of polycarbonate products

Although BPA may be found in canned beverages and foods, it occurs only

at extremely low levels (generally less than 37 parts per billion)

Why BPA is of concern?

In recent years, a “low dose hypothesis” has been advanced claiming

that exposure to extremely low doses of certain substances could cause

adverse health effects in humans, including disruption of normal hormonal

functions According to this "low dose hypothesis", reproductive and

developmental effects may result from exposure to low doses of BPA since

BPA was considered as having estrogenic activity in ovariectomized rats

(Dodds and Lawson, 1936) In 1970, Bitman and Cecil assayed DDT and 52

structurally related compounds (including BPA) in immature rats and the

authors reported an increase in uterine glycogen content According to some

scientists, BPA thus mimics estrogen, a hormone that controls the

development of the brain, the reproductive system and many other systems

in the developing fetus and therefore BPA is an endocrineđisrupting

chemical and may harm the fetuses, infants, children or subsequently, adults

What is an endocrine disrupting chemical?

Many chemicals are capable of disrupting the endocrine system of

animals including fish, wildlife, and human and are referred to as

endocrineđisrupting chemicals (EDCs) Indeed, our hormonal systems can

be disrupted by numerous different anthropogenic chemicals including

anti-androgens, androgens, estrogens, AhR agonists, steroid-hormone

antagonists, retinoid agonists, anti-thyroid substances, etc Many of the

associations between EDCs and human health effects remain controversial,

but others, like the effects of diethylstilbestrol (DES), the androgenic drugs

danazol and methyltestosterone, and aminoglutethimide are widely

recognized Recently, the increased availability of androgen products for

cutaneous application has increased the risk of virilization in children

through skin contact Estrogen containing shampoos and skin oils were

shown to be causative factors for pseudo-precocious puberty in girls and

gynecomastia in boys EDCs are not limited to pharmaceutical agents but

extend to industrial chemicals In fact, the effects of PCBs (polychlorinated

biphenyls) on human neurological and immune development are well

known Children exposed to PCBs in utero or in the early developmental

stages have lower birth weight, reduced IQ and cognitive abilities, reduced

sperm motility, and reduced in fertilizing capacitỵ Several phthalate esters,

used as plasticizers, are antiandrogens, which gives cause for concern

Nowadays, US scientists also express concern about the potential role of

ECBs in increasing trends in obesity and type II diabetes noted in the general

population

Is bisphenol-A an endocrineđisrupting chemical?

From previous investigations, BPA exhibits extremely weak hormonal

activity in in vitro assays and in laboratory animals at high doses In more

recent years, extensive studies were conducted to determine if BPA could

cause reproductive or developmental adverse effects In no study has BPA

been shown to be a reproductive or developmental toxicant The “lowđose

hypothesis” for BPA has been thoroughly tested by numerous investigators

and agencies and the consistent lack of lowđose effects found in these

studies raise doubt about the validity of the “lowđose hypothesis” Data from

the University of Arizona (Pritchett et al., 2002) indicated that, in humans,

BPA is rapidly metabolized to a hormonally-inactive form and excreted

rapidly from the bodỵ Collectively, the weight of evidence provided by these

studies demonstrates that BPA is not an endocrineđisrupting chemical and

there is no basis for human health concerns from exposure to low doses of

BPA

Is bisphenol-A a carcinogen?

BPA is not a carcinogen Based on lifetime exposure cancer bioassays

in laboratory animals, the US National Toxicology Program concluded that

BPA is not a carcinogen (NTP, 1982) The International Agency for

Research on Cancer (IARC) and the US EPA also conclude that BPA is not

a carcinogenic risk to humans (Haighton et al., 2002)

Bisphenol-A : Fear and perception

Depending on whom you talk to, BPA can be either a health risk or a

perfectly safe chemical A number of concerned parents and adults believe

that exposure to BPA during pregnancy raises the risk of cancer and

childhood behavioral problems such as hyperactivity, AĐ, and autism To

these individuals, BPA must be banned from the lining of milk bottles, can

foods and can beverages On the other hand, the US FDA, the US EPA, the

United Kingdom Standards Agency, the European Scientific Committee on

Foods and other government bodies worldwide continue to recognize BPA

as safe at low doses

I, personally, don’t think that BPA at doses found in can and beverage

linings is a risk to human health However, to err on the safe side, to limit

your exposure to BPA, do not microwave in polycarbonate plastic food

containers

Until the next time, stay health

Ts Bùi quốc Quang