SBR Latex in Construction:A Guide

SBR (Styrene Butadiene Rubber) latex is fighting against:
- polyacrylic esters (PAE) and
- styrene acrylic esters (SA)
to increase it’s market share in the polymer modified concrete industry. In this fight, we consider SBR latex the winner hands down, if we take account of both cost and performance.

In Europe we mostly use carboxylated SBRs with:

- solid contents in the region of 47-49%.

- minimum film forming temperatures round 0-3oC.

- glass transition temperatures round -5oC.


Usually they contain antifoam and antimicrobial agents.

SBR Latex modified, flexible cementitious 
coating to cover non-structural surface
 defects in new and old concrete.

MAIN ADVANTAGES OF POLYMER MODIFIED CEMENT MIXES
- Improved flexural and tensile strengths
- Better overall durability

- Reduced shrinkage

- Increased resistance to abrasion, chemicals and frost
- Improved workability for the same W/C

- Enhanced adhesion to smooth surfaces: dense concrete, steel etc.

- Suitable for potable water

- Resistant to hydrolysis.

self-leveling industrial floor materials with synthetic latex

MAIN APPLICATIONS IN EUROPE (AND GREECE)
- Amelioration of cementitious waterproofing products and tile adhesives.

- Thin, water resisting screeds, toppings, renderings, mortars etc.

- Waterproof, bonding bridges for mortars and concrete (always mixed with fresh cement and always wet on wet). Mixing proportion: 1:1,8 latex/cement by volume.

- Anticorrosion protection for reinforcements in concrete repairs (1:1 with cement by volume).

- Polymer mortars for repairs of carbonated concrete. Preventive treatments against carbonation.

SBR latex; Styrene Butadiene Latex

ACTION MECHANISMS OF SBR LATEX

1) SBR can reduce W/C for the same workability or increase workability for the same W/C. Polymer particles as well as entrained air bubbles have a ball bearing effect in the mixture. They “lubricate” the mixture particles thus reducing internal friction coefficient.

Workability improvement is further enhanced by the dispersion capabilities of the contained surfactants.

2) SBR latex due to its air entraining properties reduces bleeding considerably. This leads to an abrasion resistant surface. Though, excessive air entrainement should be avoided and most probably an antifoam agent should be used in the formula. Prolonged mixing duration entrains more air.

3) SBR latex used in cementitious waterproofing brushable products improves dramatically their water retention capability. This is a most desirable effect leading to a better hydration procedure. This water retention improvement is due to the polymer network that somehow blocks the water in the mixture.

4) SBR addition increases the water resisting properties of modified concrete and mortars.

As water evaporates, the SBR particles stick together – this is called coalescence – to form an interconnected polymer network inside the cementitious matrix. This flexible network both blocks the pores and bridges microcracks to a certain extend. Less and thinner cracks and less voids increase water impermeability.

5) SBR latex increases adhesion of aggregates to cement paste. It also enhances adhesion of cement mixes to smooth substrates: dense concrete, steel etc. This is due to the powerful bonding power of the polymer matrix.

EFFECTS OF SBR ADDITION ON PROPERTIES OF CEMENT MIXES

1. Increases tensile, flexural and impact strengths. Compressive strength remains virtually unaltered. In high dosages it could slightly decrease.

2. Overall durability increases.

3. Induced flexibility increases creep.

4. Setting times are generally reduced. Placement time also.

5. SBR addition reduces bleeding and contributes to an enhanced abrasion resistance provided that an adequate curing procedure is followed.

6. SBR latex addition increases air entrainement (despite the antifoam agent in the formula).

Types of Concrete Admixture

Chemical concrete admixtures are material in the form of powder or fluids that are added to concrete to give it certain characteristics not obtainable with plain concrete mixes. In normal use, admixture dosages are less than 5% by mass of cement and are added to the the concrete at the time of batching/mixing. The most common types of concrete admixtures are:

1. Accelerators speed up the hydration (hardening) of the concrete.

2. Retarders slow the hydration (hardening) of the concrete, and are used in large or difficult pours where partial setting before the pour is complete is undesirable.

Concrete Glue as Bonding Agent
3. Plasticizers(water-reducing admixtures) increase the workability of plastic of fresh concrete, allowing it be placed more easily with less consolidating effort. Dry sprayed concrete with setting accelerators Retarder for Concrete

Air-Entrainment

4. Air-entrainers add and distribute tiny air bubbles in the concrete, which will reduce damage during freeze-thaw cycles thereby increase the concrete's durability.

Colored Concrete: Pigment Applied

5. Pigments can be used to change the color of concrete, for aesthetics. Mainly they are ferrous oxides.

 

6. Superplasticizers (high-range water-reducing admixtures)are a class of plasticizers which have fewer deleterious effects when use to significantly increase workability. Alternatively; plasicizers can be used to reduce the water content of a concrete (and have been called water reducer due to this application) while maintaining workability. This improves its strength and durability characteristics.

7. Corrosion inhibitors are used to minimize the corrosion of steel and steel bars in concrete.

Corrosion inhibitors protect steel against corrosion by promoting a chemical reaction on the surface of the steel rebars. They interrupt the electrolytic current to produce a sharp reduction of corrosion

8. Bonding agent are used to create a bond between old and new concrete. Pumping aids improve pumpability, thicken the paste and reduce dewatering of the paste.

Thus, chemical admixture is one ingredient creating concrete that provide the differentiation of concrete types.

Above The Ground & Under Ground Rainwater Tanks

Rainwater tanks can be placed anywhere you want them to be, provided it is conducive to its working. It is of utmost importance that the inlet is right below the guttering if you want to harvest rain water from the roof. You will find many different shapes of tanks which can be placed either above the ground or under it.

Let’s find out the pros and cons of both.

While the availability of space is very important factor to decide the placement of your rainwater tank, its quite obvious that above the ground rainwater tanks occupy more space than ones installed below. Underground tanks actually save some space for you and don’t get in your way.

Underground rainwater tanks need a pump to extract because of its unusual placement which is an added expense.  A pump is not a compulsory requirement for rain water tanks installed above the ground and lets good old gravity work its magic. Detecting malfunctions and leaks is really difficult in underground rain water tanks; it is relatively easier in tanks above the ground. In underground rain water tanks weather changes are not a big problem.

Torrential rains and extreme heat and cold may have an adverse effect on tanks installed above the ground; they can catch fire or get damaged during heavy showers and strong winds. When rain water tanks are installed below the ground, roots of trees can hamper its structure and also contaminate the water, this quite naturally is not an issue with above the ground rain water tanks. You can opt for rainwater tanks that are uncovered if they are installed above the ground but not in ones installed underground. It is not safe and has the risk of soil, faeces, pesticides entering it during rains as surface run offs. Installing above the ground rain water tanks is much easier and doesn’t require excavation as in the case of rain water tanks installed below. Maintenance of poly rain water tanks above the ground is much easier as well.

Weigh out all your options before installing your rain water tank. You also have the chose the type and shape of the tank. You can choose between steel, wood, concrete, fibre glass and polyethylene (poly) water tanks. There are also many shapes you can choose from. There are round tanks that are very popular all over the world and that can hold a large capacity of water. You can also go in for the slimline tanks that are great on the side of a wall and behind the house. You also have rain water tanks that are ornate and specifically designed to add to the façade of the house and many more to chose from.

What is Seismic Body Waves

Whenever the earth is suddenly struck or disturbed  due to earthquake vibration are produced. These vibrations are setup or start from a limited area and are propagated outward in all directions. Thus an earthquake may be defined as the passage of these vibrations in the earth.

Body waves consist of two waves. These are

a) Primary waves ( P-waves)

b) Secondary Waves (S-waves)

a) Primary waves

1) Nature : These are longitudinal or compressional in nature. Therefore it is known as longitudinal waves or compressional waves.

2) Direction of Particle Vibration : The rock particles vibrates in the direction of propagation of the waves, with a push and pull effect.

3) Speed : It is the fastest waves and therefore first to be recorded at the recording station. It travels with about the same speed as sound through same rock.

4) Example : In granites, P -waves have speed of about 4.8 Km/Sec.

5) Penetration Capacity : These waves are capable of passing through solids as well as liquides.

b) Secondary Waves :

1) Nature: These are transverse or distortional in nature. Therefore it is known as transverse waves, shear waves or shake waves.

2) Direction of Particle Vibration: The rock particles vibrate at right angles to the direction of propagation like light waves.

3) Speed: These travel slower than the P-waves and are second to be recorded.

4) Example: In granites, S-waves have speed of about 3 km/sec.

5) Penetration capacity: These can pass through solids but it is in capable of passing through liquids.

What Do Stair Lifts Cost?

What do stair lifts cost? The cost of a stair lift is dependent on many factors. A stair lift is a great accessibility option for the elderly, handicapped and other mobility challenged people who have difficulty in walking and moving up and down the stairs. With a stair lift, they can enjoy moving about their multistoried apartment with minimum or completely no assistance from others.

Factors Affecting the Stair Lift Cost

The price of stair lifts may vary according to various factors. In the market, there are so many models of stair lifts available and the price depends on specific features, size, shape, level of automation, quality, and more.

There are different types of stair lifts: straight stair lifts, stair lifts for curved stairs, wheelchair platform lifts, outdoor stair lifts, Bruno stair lifts, pre-owned or used stair lifts and goods stair lifts. Stair lift prices depend on what type of stair lift you are planning to purchase.

Listed here are some of the factors that affect the stair lift cost:

1. the various functional and safety features included

2. the length of your stairs

3. whether the stair lift is battery powered (expensive) or AC operated

4. Whether it is an outdoor stair lift (expensive) or an indoor one

5. Whether it is a straight stair lift or a curved stair lift (expensive). A straight stair lift is less expensive. This type of stair lift can be purchased for around $1500. A curved stair lift could start at around $4000 and cost upwards of $10,000.

The shape of your staircase and the length of the track also affect the cost of a stair lift. The quality of stair lifts and accessories that you might choose to add will also have an effect on the cost. For instance, many people opt to add a swivel chair, folding arm rests, fold-out foot plates, or grocery baskets and this will raise the cost of stair lifts. Normally, you could say that most accessories will each add about $200 to the overall cost.

If you want one that is of a top range and a great model with lots of safety features, then obviously you have to pay a good price for that. It is important to decide which stair lift ideally fits your stair case. If you can't decide on which stair lift to choose for your stairs, you can seek assistance from a stair lift company of your choice. Make sure to choose a reliable manufacturer so that you will get a price list that includes the right price range for different types of stair lifts. Or, simply visit a dealer website or any shop to make a comparative study of the cost of stair lifts.

What is Rivet?

The components which make up the complete metal member or structure are fastened together by means of rivets, bolts, or welds. Rivets are made from rivet bar stock in a machine which forms one head and shears the rivet to the desired length. Rivet heads are usually of a rounded shape called a buttonhead. The head may be flattened when clearance is limited. When very little clearance is available, countersunk heads are used. Countersunk heads are chipped flush if no clearance is available. Information concerning conventional signs for riveting, sizes of heads, weights, lengths, and other data are given in the AISC steel construction manuals.

Steel rivets are almost always heated before driving. In the shop the rivet is heated to a minimum temperature identified by a light cherry-red color. Most shop rivets are driven by pressure-type riveters which complete the riveting operation in one stoke.

Riveting guns are portable hand tools, operated by compressed air, which drive the rivet by a rapid succession of blows.Rivets are made from steel conforming to the specifications for rivet steel, ASTM A502. this specification covers two grades of steel. Grade 1 is a carbon steel for general purposes. 
 

Grade 2 is a carbon-manganese steel for riveting high- strength alloy structural steels. Rivet heads are marked to identify the manufacturer and with a numeral 1 or 2 to identify the grade; the manufacturer may omit the numeral 1.

6053-T61 Aluminum

Rivets used in fabricating structures of aluminum alloys may be driven either hot or cold. Cold-driven rivets for structures of alloy 6061-T6 and 6062-T6 are made from alloy 6061-T6 and for structures of 6063-T5 and 6063T6 from alloy 6053-T61. cold-driven rivets for structures of alloy 2014-T6 are made from alloy 2117-T3. hot-driven rivets for the five alloys are made from alloy 6061-T43.

Economical Proportioning of Trusses

Figure below shows the common types of simple-span bridge trusses. By varying the depth of a truss throughout its length (fig. c), forces in the chord members can be more nearly equalized and the forces in the web reduced.

Trusses of economical proportions usually result if the angle between diagonals and verticals ranges from 45⁰ to 60⁰. However, if long-span trusses are made deep enough for adequate rigidity as well for economy, a suitable slope of the diagonals may produce panels too long for an economical floor system.

Some bridge trusses are shown in figures above:

a) Pratt truss through bridge

b) Pratt truss deck bridge

c) Curved-chord Pratt truss

d)

d) Warren truss with verticals

f) Subdivided Pratt truss; known as Baltimore truss

g) Petit or Pennsylvania truss

h) K truss

Baltimore truss

The subdivided panels of Baltimore and petit trusses (fig. f and g) solve this problem. Certain objections to subdivided panels were overcome with the invention of the K truss (fig. h).

Characteristic of Quicklime

The special characteristic of quicklime is its ability to slake with water. When quicklime is mixed with from two to three times its weight of water, a chemical reaction takes place. The calcium oxide combines with water to form calcium hydroxide, and sufficient heat is evolved to bring the entire mass to a boil. The resulting product is a suspension of finely divided calcium hydroxide (and magnesium hydroxide or oxide if dolomitic lime is used) in water. On cooling, the semifluid mass stiffens to a putty of such consistency that it may be shoveled or carried in a hod. This slaked quicklime putty, when cooled and preferably screened, is the material used in construction. Quicklime should always be thoroughly slaked.

The yield of putty will vary, depending on the type of quicklime, its degree of burning, and slaking conditions, and will usually be from 70 to 100 ft³of putty per ton of quicklime. The principal use of the putty is in masonry mortars, where it is particularly valuable because of the high degree of plasticity or workability it imparts to the mortar. It is used at times as an admixture in concrete to improve workability.

What is Sealed Sample for Test?

A sample shall be treated to be "sealed" if it is received in the laboratory in the following condition:

 All sealed samples should be properly wrapped, gala-sealed and signed by the person having signature in the forwarding letter.

Sample shall be packed/wrapped with cloth or paper in a manner so that contents of the pack cannot be removed/altered without tearing the seal and signature.

Sealed Soil Sample

Having sample bags printed in manner as shown in figure above(Sampling Bituminous Mixes)can be very useful for recording information until such time as you can write a sample certificate

Samples not meeting these requirements shall be considered to be "Unsealed". 

Steel and Aluminum Towers

Towers are used to support transmission lines, radio and television antennas, radar and microwave equipment, tanks, bridges, etc. freestanding towers (such as transmission towers and some radio and television towers) are usually rectangular in plan.




The tall towers used in the electronic industry are usually guyed. The plan is usually an equilateral triangle, with the legs at the vertices. Most steel-tower members are hot dipped galvanized for weather protection.

Aluminum towers are usually made of alloy 6061-T6, which is corrosion- resistant in all climates without surface protection. It can be extruded to produce optimum shapes for resisting stress and simplifying joints. Because of their lighter weight, aluminum towers can be flown by helicopter to relatively inaccessible sites.

Base Plate for Steel Column

The base of a column which is supported by a concrete footing must have a bearing plate large enough to distribute the load over an area sufficient to preclude excessive bearing stresses. The base plate may be shop-connected or shipped loose. Except where end moments are involved, the connection need only hold the parts in line if the ends of the column are finished to a plane surface, since the load is transmitted by bearing at the contact surfaces.

It may be cheaper to omit planning the ends of lightly loaded columns and to design the connection between base and shaft for the total load. The distribution of the pressure of the plate on the footing depends upon the relative stiffness of the two. Even if the distribution were known, the resulting stresses in the plate could not be determined easily since bending in two directions is involved. The usual analysis is based on two assumptions:

1. The pressure of the footing on the plate is uniformly distributed

2. Those portions of the plate which project from the column shaft act as cantilever beams. Since the sections of zero share, and consequently of maximum moment, in the bearing plates are inside the area of contact between the column shaft and plate, the length of the cantilevered portions are usually assumed to be longer than the actual projection o the plate. 


The AISC recommended analysis for H-shaped columns assumes that the maximum moments occur at sections which are 0.95d apart in one direction and 0.8b apart in the other direction, where d and b are, respectively, the depth and flange width of the shape.

Bases of columns in industrial buildings, and those in tier-building construction designed to resist wind forces, may need to be proportioned to resist end moment resulting from lateral forces.

Under-Reamed Piles: Safest Foundation Solution for Black Cotton soil

Swelling and shrinkage due to the property of volumetric changes of expansive soil like black cotton soil results movement of the ground producing cracking of the order of (sometimes) 15 to 20 cm wide and 2.5 to 4 m deep. This property is very dangerous for the structures supposed to be founded on it. Many techniques are discussed previously in various post published in this blog. Some of these are provision for reinforced concrete ties or bands all around the main walls of the building, removing entire black cotton soil where possible or commencing construction during dry seasons. 

It is found that under-reamed piles provide an ideal solution to foundation in black cotton soil or other similar types of expansive soils. The design guidelines of under-reamed pile are briefly discussed below:

Under-Reamed Pile Foundation for Black Cotton Soil

Design guidelines for Under-Reamed Pile Foundation

The diameter of the pile stem (D) varies from 20 to 50 cm. The diameter of the under-ream bulbs (D_u) is normally 2.5 times the diameter of the pile stem. It may however, vary form 2 to 3 times (D) under special circumstances. In case of double or multi-under-reamed piles, the centre to centre vertical spacing between two bulbs may vary from 1 ¼ to 1 ½ times the under-reamed diameter (D_u). The length of under-reamed piles varies from 3 to 8 meter and their centre to centre spacing should normally be not less than 2 times the under-reamed diameter.  

What is Batter Pile?

Batter pile shall be used to transfer inclined load and horizontal forces. In the preliminary design, the load on batter pile is generally considered to be axial.


The distribution of load between batter and vertical piles in a group may be determined graphically or by analytic methods. Due consideration shall be given to secondary bending as well as pile cap movement, particularly when the cap is rigid.


Free standing batter piles are subjected to bending moment due to their own weight, or external forces from other sources.


Batter pile in loose fill or consolidating deposits may become laterally loaded due to settlement of the surrounding soil. In consolidating clay, special precautions, like provision of permanent casing, shall be taken. 

Lateral Capacity of Pile

One of the most common and most widely used deep foundation is pile. It is generally much more expensive than the shallow foundation and feasible only when a firm stratum is so deep that it can not be reached economically by shallow foundation.

Lateral capacity of vertical single piles shall be the least of the values calculated on the basis of soil failure, structural capacity of pile and deflection of pile head.

Deflection calculations required horizontal subgrade modulus of surrounding soil. When considering lateral load on piles, the effect of other coexistent loads, including axial load on the pile, shall be taken into consideration for checking structural capacity of the shaft.

For estimating depth of fixity, established method of analysis shall be used, or lateral load test to at least twice the proposed design working load shall be made. The resulting allowable load shall not be more than one-half of the test load which produces a gross lateral movement of 25 mm at the ground surface.

All piles standing unbraced in air, water or soils not capable of providing lateral support shall be designed as columns in accordance with the provision of ACI code.

USC University Hospital, California: The Tested U.S. Base Isolated Building

The University of Southern California Teaching Hospital in east Los Angeles (1991) had a severe test in 1994, when the Northridge earthquake hit.

Though it was only 23 miles from the epicenter, the horizontal acceleration in the building was three or four times less than the peak acceleration outside: the building was effectively isolated from the motions that caused significant damage to buildings nearby.

During the 1994 Northridge earthquake, the isolators reduced the accelerations by 66% at the base and 40% at the roof.

BUILDING PROFILE
1.	LENGTH	92.35-m (303-ft)
2.	WIDTH	77.11-m (253-ft)
3.	BAY
	EAST-WEST(EW)	10
	NORTH-SOUTH (NS)	12
4.	IRREGULARITIES
	PLAN	Asymmetric with two wings, which are connected by a necked down region of the floor/base
	VERTICAL	The building has setbacks after the fifth floor
5.	STORY	Seven stories above the ground and a basement
6.	SUPERSTRUCTURE	Steel-braced framed building
7.	SUBSTRUCTURE	Reinforced concrete base slab

 

Fig. 1(a)

Fig. 1(b)

Fig. 1 shows the plan and elevation of the building. Metal decking and a grid of steel beams support all concrete floors. The superstructure bracing is located at the building perimeter. The steel superstructure is supported on a reinforced concrete base slab, which is integral with the reinforced concrete beams below, and drop panels below each column location.


 The isolators are connected between these drop panels and the footings below [Fig. 1(b)]. The footings also support a reinforced concrete pedestal provided for backup safety. The seismic isolation system consists of 68 lead-rubber isolators and 81 elastomeric isolators, as shown in Fig. 1. The building is located near the intersection of Highways 5 and 10.

The closest active faults to the site are the Raymond Fault and the Newport-Ingelwood Fault. The building was designed using spectrum compatible earthquakes—with the spectrum defined as 1.2 times the 0.4g ATC-3-06 or UBC spectrum.

Effects Of Using Polycarbonated Plastics

In today's world ‘plastic' is the substance that is being widely used by people for their daily course. Be it from carrying things in a polythene bag or store grains in plastic containers or storing water in PET bottles etc. Also in this fast pace life the stored food with preservatives is consumed widely all over the world which is mainly preserved in metal cans.

But these cans and the PET bottles is a poison for the person who uses it.

Now the question arises how it is harmful to the humans?

Many transparent 'plastic' bottles are made from polycarbonate, usually a polymer of ‘Bisphenol A'.

In this paper, mainly the harmful effects of Bisphenol A in the human life are discussed.
 

First synthesized in 1891, the chemical has become a key building block of plastics from polycarbonate to polyester; in the U.S. alone more than 2.3 billion pounds (1.04 million metric tons) of the stuff is manufactured annually. Bisphenol A also known as BPA, is used in the preparation of the polycarbonate plastic and epoxy resins, both of which are used in a wide variety of applications that make our lives better and safer.

Polycarbonate Plastic Sheet

POLYCARBONATE: A transparent thermoplastic material

Also it is an industrial chemical that has been present in many hard plastic bottles and metal based food and beverage cans since 1960. 

The polycarbonate plastics made using BPA are used in many food and drink packaging applications while the epoxy resins are commonly used as lacquers to coat the metal cans or bottle caps or water supply pipes.    

Harmful effects:

According to the scientists of University of Cincinnati (UC), the temperature of the liquid has a great impact on how much BPA is released. It is found by Schott Belcher and his team when the polycarbonate drinking bottle is exposed to boiling hot water, the amount of BPA released 55 times more rapidly than before exposure to hot water.

In Feb 2008, Belcher stated that, "There is a very strong suspicion in the scientific community, however, that this chemical has harmful effects on humans, as little clinical evidence related to humans have been found."

In another research carried out in the same University by A research team lead by Scott Belcher, PhD, Hong Sheng Wang, PhD, and Jo El Schultz, PhD, in the department of pharmacology and cell biophysics, found that exposure to BPA and/or estrogen causes' abnormal activity in hearts of female rats and mice. BPA, an environmental pollutant with estrogen activity, is used to make hard, clear plastic and is common in many food product containers. It has been linked to neurological defects, diabetes and breast and prostate cancer.

Polycarbonate Plastic Roof Panels

Belcher and team found that the presence of BPA in the cells caused an increased the release of calcium from sarcoplasmic reticulum – the part of cardiac muscle that stores and release the calcium ions indicating spontaneous release that's likely causing irregular heart beats and may have other harmful actions, especially following heart attack.

In female cardiac muscle cells, the blocking or genetic removal of estrogen receptor beta completely blocked the contractile effects of BPA and estrogen, while in males, blockade of the effects of estrogen receptor alpha caused the male heart to become more 'female-like' and become responsive to estrogen and BPA.

These studies enable us to identify the major cardiac risks after a long term exposure to BPA for a woman's health.

The U.S. Centers for Disease Control (CDC) found that traces of BPA appeared at levels ranging from 33 to 80 nanograms (a nanogram is one billionth of a gram) per kilogram of body weight in any given day levels 1,000 times lower than the 50 micrograms (one millionth of a gram) per kilogram of bodyweight per day considered safe by the U.S. Environmental Protection Agency (EPA) and the European Union's (E.U.) European Food Safety Authority (EFSA).

BPA once ingested is broken down to glucuronide a waste product that is easily excreted. Yet CDC found glucuronide in most urine samples collected in 2004, suggesting constant exposure to it glucuronide in most urine samples, suggesting constant exposure to it.

Chemist Steven Hentges, executive director of the polycarbonate / BPA global group of the American Chemistry Council states that, ‘there is a constant low-level exposure to the chemical presumably in our diet.'

Fred vom Saal, a reproductive biologist at the University of Missouri–Columbia, warns that babies likely face the "highest exposure" in human populations, because both baby bottles and infant formula cans likely leach BPA and according to him, "In animal studies, the levels that cause harm happen at 10 times below what is common in the U.S."

Tim A. Osswald, an expert in polymer engineering at the University of Wisconsin–Madison stated that during the manufacturing process, not all BPA gets locked into chemical bonds. That residual BPA can work itself free, especially when the plastic is heated, whether it's a Nalgene bottle in the dishwasher, a food container in the microwave, or a test tube being sterilized in an autoclave.

Bisphenol A is a known endocrine-active chemical. Low-level human exposure is widespread due to the chemical's presence in polycarbonate plastic and epoxy resins, but understanding long-term consequences of exposure will be challenging. According to Frederick vom Saal, it is a fundamental part of endocrinology, and it is beautifully demonstrated, that stimulation at the cerebellar cell surface receptor is able to cause effects at doses below a part per trillion. Not only are the doses many magnitudes lower than those considered in classic high-dose toxicity studies, but at extremely low dose bisphenol A demonstrate a response that disappears as the dose increases. As the dose increases there is always an increase in response, and hence it is challenging to study the effects of bisphenol A.

Bisphenol A at Low Nanomolar Doses Confers Chemoresistance in Estrogen Receptor Alpha Positive and Negative Breast Cancer Cells

Effects at even low BPA exposure include prostate cancer, breast cancer, early puberty onset, alterations in gender-specific behavior, decreased sperm count, affects on fertility, behavioral effects including hyperactivity, increased aggressiveness, impaired learning and other changes in behavior, and other problems. And, astonishingly, BPA is found everywhere making human exposure widespread.

Precautions:

Baby bottles and sippy cups:

AVOID bottles such as Dr. Brown's, Avent, clear Evenflo, FirstYears, Platex VentAire, Sassy and TupperCare as they are all contain bisphenol A. On the sippy cup side, avoid Nuby cups with handles coming up from the bottom of the cup, Gerber Soft Starter, and Gerber Suzy's Zoo & Sippy Snacker.

BPA-free bottles and sippies flagged as safe include: glass bottles, Born-Free, Medela breast milk storage bottles (made with polypropylene) and disposable bottle systems that have polyethylene plastic inserts.

If you must use a bottle/sippy made with BPA, you should NEVER store milk in a container in it, as the chemical could leach into the milk.

You should also discard any bottles that are scratched, appear cloudy or generally have an altered appearance from their "new" look.

Exposing to heat, harsh detergents (no dishwashers) and microwaving can cause leaching

It's in the lining of canned foods, where it appears to be the most common way to be exposed. BPA can leach into the food inside the can.

It's especially important to note that infants fed canned formula are at the greatest risk.

Not all the plastic food containers are made up using BPA, but care should be taken while using them so that other chemicals do not leach into the food products.

There are 7 different types of plastics out of which type 1, 2, 4 and 5 are safe fro storing food while type 3, 6, and 7 are not, with 7 being BPA.

  

Conclusion:

It is also important to note that the studies that found the harmful effects were government funded. The industry-funded studies did not find any threat to humans, so if you embark on your own search on bisphenol A, please make sure to note if the study was industry-funded. They have a way of hiding things to protect their bottom line. Searching for and manufacturing safer alternatives can be costly.

Hence, from the above discussion it can be concluded that human exposure to bisphenol A is very less but is increasing rapidly.

Scientists are looking for microbial ways to degrade it to simpler compounds so that the harmful effects can be avoided.

Thus, always heat food in a microwave safe container, glass is best bearing the pain of washing an extra dish is better than that of chemotherapy. It's your choice of selecting the pain you want to bear.