How Much Arsenic Do We Eat? Analytical chemists make light work in tracking potentially harmful chemicals Julian Tyson Department of Chemistry UMass Amherst.

How Much Arsenic Do We Eat?

Analytical chemists make light work

in tracking potentially harmful chemicalsJulian Tyson

Department of Chemistry

UMass Amherst

Analytical chemists provide information about the chemical composition of materials. So that a decision can be taken.

Interaction of light with materials.

How do analytical chemists make light work in tracking potentially

harmful chemicals?

Light is a wave and is a form of energy. The energy of light is inversely related to its wavelength.

Short wavelength: high energy.Long wavelength: low energy

Summary of where we are now.

Color of objects is due to the absorption of light.

Absorption is due to the molecules.

The wavelengths of the light absorbed tell us something about which chemicals are present.

Amount of light absorbed depends on the number of molecules in the light beam, so

The extent of the absorption tells us something about how much of a chemical is present.

Analytical chemists use the interaction of light with with molecules that contain arsenic to measure the arsenic in relevant materials.

So how does arsenic get into relevant materials?

Arsenic occurs in nature. It is about the 40th most abundant element on the planet. Geological processes have spread it around. We’ve extracted it from ores, made useful compounds and spread them around.

Open ocean water: about 1 - 4 ppb

River and surface water: about 0.1 - 1 ppb

Realgar As4S4

Arsenic trioxide As2O3 Arsenic As

Orpiment As2S3

The arsenic in the environment story

Ground water: a major problem around the world. Especially in SE Asia (Bangladesh and West Bengal, India)

Concentrations: 0.1 – 1000 ppb.

US EPA limit is 10 ppb

Concentrations in soil are about 2 mg kg-1. But there are considerable variations and there’s a legacy of previous agricultural practice to deal with.

Amounts. Volume:

liter (L) = 0.26 gallon (US) = 1,000 milliliters (mL)1 milliliter (mL) = one-thousandth of a liter1 microliter (µL) = one-millionth of a liter

A drop (of water) is about 50 µLA bathtub contains about 230 L

Concentrations in solids: mass per mass 1 part per million (ppm) is 1 milligram in 1 kilogram i.e. 1 mg/kg or 1 microgram in 1 gram i.e. 1 µg/g

Scientist sometimes write this as 1 µg g-1

A part per billion (ppb) is 1 µg kg-1

Concentrations in liquids: mass per volume 1 part per million (ppm) is 1 milligram in 1 liter i.e. 1 mg/L or 1 microgram in 1 mL i.e. 1 µg/mL

Scientist sometimes write this as 1 µg mL-1

A part per billion (ppb) is 1 µg L-1

1000 ppb = 1 ppm

One grain weighs 65 mg(2.5 mm cube of As2O3)76% by weight is As49 mg

21 bathtubs contain 21 x 233 L = 4,900 L

1 grain in 21 bathtubs = 10 ppb

The US EPA limit for arsenic in drinking water

How to make a 10 pbb solution

Arsenic speciation

There are a lot of different arsenic compounds in the environment. Inorganic

Arsenic bonded to oxygen and/or sulfur or hydrogen.

As2O5 H3AsO4 arsenateAs2O3 H3AsO3 arseniteAsH3 arsine

Organic

Arsenic bonded to carbon and/or oxygen or hydrogen

Methylated arsenate

CH3AsO(OH)2 MMA(CH3)2As(O)OH DMA

Arsenobetaine, arsenocholine

Some formulae for the chemists in the audience.

arsenite

dimethylarsinate

arsenate monomethylarsonate

cacodylate

trimethylarsine oxide

More formulae for the chemists in the audience.

trimethylarsine oxide tetramethylarsonium

Yet more formulae for the chemists in the audience.

arsenocholine

Seafood arsenic

TETRA

arsenobetaine

Not all arsenic compounds are very toxic

Some arsenic compounds are “non-toxic.”arsenobetaine and arsenocholine and arsenosugarsseafood arsenic

OK - all chemicals are toxic: it all depends on the dose and how you interact with them.

Some arsenic compounds are toxicAcute lethal dose of As2O3 is about 100 mg for a 70-kg adult.About 2 grains or a 3 mm cube.

Some arsenic compounds are sort of non-toxicMonomethyl and dimethyl arsenates

The adverse health effect of concern is cancer.

How does arsenic get into our food? Plants take up arsenic compounds from the soil. Legacy of previous applications.

How arsenic gets into crops

How do we know whether food and drink contains potentially harmful forms of arsenic?

Ask the analytical chemists. They tell us.

• Seafood contains non-toxic forms

• Drinking water contains toxic, inorganic forms

• Food contains toxic (inorganic) and sort-of toxic forms (mono- and di- methylated).

Approach: Measure total arsenic and assume it is all toxic.

If less than guideline value: no problem

If more than guideline value: more analysis needed

How much arsenic is considered safe?

How much inorganic arsenic is considered safe?

Food: No US guideline value.Drinking water: US EPA 10 µg L-1 (ppb)

Joint FAO/WHO expert committee on food additives, seventy-second meeting, Rome, 16–25 February 2010, summary and conclusions Issued 16th March 2010 http://www.who.int/foodsafety/chem/summary72_rev.pdf

The limit for dietary inorganic arsenic exposure is:

3.0 µg per kg body weight per day

How much inorganic arsenic is considered safe?Dietary: 3.0 µg per kg body weight per day.

Developmental stage

Weight lbs1 lb = 0.45 kg

Tolerable daily

intake µg

Newborn 7 9

1-year-old 22 30

5-year-old 42 57

teenager 140 (m) 117 (f) 191 (m) 160 (f)

young adult 155 (m) 127 (f) 211 (m) 173 (f)

Adult (US average) 191 (m) 164 (f) 260 (m) 224 (f)

football player 300 409

overweight your call > 400

Acute lethal dose (adult) 100 mg

How much inorganic arsenic do we actually eat?Food: Ask the analytical chemists.

Developmental stage

Weight lbs1 lb = 0.45 kg

Tolerable daily

intake µg

Newborn 7 9

1-year-old 22 30

5-year-old 42 57

teenager 140 (m) 117 (f) 191 (m) 160 (f)

young adult 155 (m) 127 (f) 211 (m) 173 (f)

Adult (US average) 191 (m) 164 (f) 260 (m) 224 (f)

football player 300 409

overweight your call > 400

Acute lethal dose (adult) 100 mg

Food and Chemical Toxicology 37 (1999) 839-846

Examined 40 commodities expected to deliver 90% of total dietary inorganic arsenic. Took 4 samples of each. Measured total arsenic and inorganic arsenic.

A market basket survey of inorganic food in rice

Food Total arsenic µg kg-1 wet weight

Inorganic arsenicµg kg-1 wet weight

saltwater finfish 2,400 0.5

shrimp 1,900 2

tuna 512 1

rice 303 74

chicken 86 1

grape juice 58 9

beef 52 0.4

peanut butter 44 5

watermelon 40 9

flour 39 11

spinach 5 6

apple juice 8 3

Inorganic arsenic.

Environmental Health Perspectives, 2010, 118, 345-350

Probabilistic modeling of dietary arsenic exposure and dose and evaluation with 2003-2004 NHANES Data

Scientists at US EPA, National Taiwan University, and the Environmental and Occupational Health Sciences Institute

24

12

1718

13

11

5

Environmental Health Perspectives, 2010, 118, 345-350

Results: Mean total exposure from food is 0.38 µg per kg body weight per day. 14-times higher than the mean exposure from drinking water. Exposure from food is 0.05 µg per kg body weight per day i.e. 1.96 µg per day.

Approximately 10% of exposure from food is the toxic inorganic form of arsenic.

The average American weighs 40 kg i.e. 88 lbs.

Age Number Average 5th percentile

99th percentile

0 - 1 757 0.62 0.05 2.08

1 - 2 1,068 0.54 0.05 5.06

3 -5 963 0.54 0.03 5.6

6-12 2,190 0.37 0.02 4.28

13 -19 3,576 0.25 0.01 3.58

20 - 49 4,221 0.33 0.01 4.12

>50 3,804 0.32 0.01 4.91

All 16,931 0.36 0.01 4.45

Calculated exposure from food. Total arsenic: µg per kg body weight per day

Age Number Average 5th percentile

99th percentile

0 - 1 757 0.23 0.01 0.8

1 - 2 1,068 0.1 0.01 0.59

3 -5 963 0.08 0 0.4

6-12 2,190 0.04 0 0.25

13 -19 3,576 0.03 0 0.21

20 - 49 4,221 0.03 0 0.28

>50 3,804 0.03 0 0.22

All 16, 931 0.05 0 0.41

Calculated exposure from food. Inorganic arsenic: µg per kg body weight per day

Food Total arsenic µg kg-1 wet weight

Inorganic arsenicµg kg-1 wet weight

rice 303 74Total

arsenicInorganic MMA DMA I + MMA +

DMA%

missing

335 55 ND ND 55 84

218 62 ND 61 123 44

462 81 3 202 286 38

196 97 2 99 198 0

There’s a problem with the Schoof analysis of the rice.

The Schoof report: A market basket survey of inorganic food in rice

What do other researchers find about arsenic in rice?

Survey of total arsenic and arsenic speciation in US-produced rice as a reference point for evaluating change and future trends.

Heitkemper and colleagues at USFDA Cincinnati

The average total content was 210 µg kg-1.

Regardless of total content, inorganic arsenic rarely exceeded 150 µg kg-1.

Arsenic content in US rice has been relatively constant over the past 30 years.

Food Additives and Contaminants: Part B, 2009, 2, 112-120

Date Location Total Inorganic % missing*

1980-81 LA 167 105 -9

1980-81 AR 184 79 -11

1980-81 TX 445# 111 0

1980-81 CA 62 61 -33

1980-81 AVE US 202 90 -13

2001-02 AVE US 264 98 -11

#One sample had over 1000 µg kg-1 total: inorganic 150 µg kg-1

All values in µg kg-1 based on dry weight.

*The minus sign means that the sum of I + MMA + DMA > total

“In comparison with inorganic arsenic, much less is known regarding the toxicity and biotransformation pathways associated with dietary intake of DMA.

Although generally considered to be less toxic than inorganic arsenic, more information about the long-term exposure effects of DMA may be necessary to evaluate fully the risk of rice consumption, given the high DMA content that has been reported in rice.”

Heitkemper and colleagues at US FDA Cincinnati

Conclusions

What do other researchers find about arsenic in rice?

Meharg and colleagues at the University of Aberdeen

Arsenic in rice around the world. All values in µg kg-1

Location Average Total

Max total Average inorganic

Max inorganic

Bangladesh 130 330 80 210

China 140 460 160 380

Egypt 50 580 No data No data

France 280 560 No data No data

India 70 180 30 70

Italy 150 330 110 160

Japan 190 420 No data No data

Spain 200 820 No data No data

Thailand 140 390 No data No data

USA 250 660 100 150

“The modeling outlined here indicates that eating rice at typical SE Asia consumption rates, or at higher percentile consumption rates in developed countries, constitutes a significant excess cancer risk to those populations, well above the targets set by US EPA and WHO for carcinogenic sources.”

“As cancers caused by chronic exposure to arsenic sources have a latency of approx. 20 years, the data presented here suggest that long-term epidemiological studies need to be undertaken to characterize this risk.”

Meharg and colleagues at the University of Aberdeen

Conclusions

Researchers call for monitoring of arsenic levels in rice

By Elizabeth Weise, USA TODAY Dec 5, 2011

Proceedings of the National Academy of Sciences of the USA Dec 5th 2011

Rice consumption contributes to arsenic exposure in US women

Diane Gilbert-Diamond and coworkers at Dartmouth College

“Emerging data indicate that rice consumption may lead to potentially harmful arsenic exposure.”

“Although inorganic arsenic is thought to be more harmful that DMA, further epidemiological studies are needed to better understand the health risks of DMA . . . It is imperative that the health impact of arsenic exposure through rice consumption be characterized.”

www.pnas.org/cgi/doi/10/.1073/pnas1109127108

How Much Arsenic Do We Eat? The question really should be: How much inorganic

arsenic and methylated arsenic do we eat?

Answer: depends on what foods we eat. Rice has a much higher concentration than any other food.

What sort of rice, where from and how much.

White rice contains less arsenic than brown rice.

Where grown. USA, France, and Spain (max total)China, Bangladesh and Italy (max inorganic).

Bioavailable? Assume 100%.

So. What about apple juice?

88 samples purchased in Aug and Sept 2011 in CT, NJ, and NY.

There’s no federal limit for arsenic in juice. 25% of samples exceeded 5 ppb and 10% exceeded 10 ppb.

Recommended dietary limit is 3 µg per kg body weight per day.

30 - 60 µg for young children.

Need to drink 1.2 – 2.4 L

i.e. 2.5 – 5 pints per day.

Take digital picture with digital camera.