Arsenic:Science

Regulation and

Public Policy

Lecture at Harvard School of Public Health

12.30 pm, Friday May 4th 2001

by

Richard WilsonMallinckrodt Research Professor of Physics

Harvard University

ARSENIC

Metal

Molecular weight 74.92

Melting Point 8170C

Specific Gravity 5.73

Many compounds and minerals

• Arsenic has been used for over 3000 years

• As2O3 ARSENLITE

• by roasting As2S or FeAsS

• As2S3 ORPIMENT

• PbHAsO4 SHULTENITE

• KH(ASO2)2 Fowler’s Solution

• CH3AsO(ON2)2

• CH3AsO(OH)ONa

• Pesticides with various names

Non-Ferrous Smelters

Coal Burning

Cotton Gins

Cigarette smoke

Common Sources

Early Information(pre 1986)

Acutely Toxic

to Rodents and People

Used as Medicine

Fowler’s solution 1% in alcohol

Cure for Syphilis

(recent) cure for leukemia

Early Information(pre 1986) contd.

1888 Skin lesions and Cancers

1897 Lung cancer from pesticides

1920s lung cancer from smelters

1950s angiosarcoma from pesticides

BUT

no cancers in rodents

Early Misconception(pre 1986)

Rodents dont get cancer,

therefore people wont

Inhalation a special case

with non-linearity

(but Zeise and I contested that)

Preliminary warning

• TSENG et al found skin Tumors in TAIWAN

• BUT

• They appeared to follow a threshold relationship.

THE GREAT SURPRIZE

In 1986 C J Chen

And collaborators reported internal cancers in the same

area of Taiwan

IGNORED FOR 5 YEARS!

Why?

Only a Chinese study

(as bad as the Russians?)

1990 Allan Smith

1991 Byrd,Lamm Wilson

took him seriously

THE GREAT SURPRIZE

The internal cancers seemed to be linear with dose and the risk is

huge.

BUT:

An ecological study

and

Only in one location and there might be another cause

THE VINDICATION

CHILEARGENTINEINNER MONGOLIABANGLADESHWEST BENGAL

NO PREVIOUS STUDY INCONSISTENT

LOW DOSE LINARITY the regulatory default

• Crump Guess and Peto of 1975

CRITICAL ISSUES FOR LINEARITY

• The POLLUTANT ACTS

• in the same way as

• WHATEVER ELSEINFLUENCES THE

• CANCER RATE

• CANCERS CAUSED BY

• THE POLLUTANT

• ARE INDISTINGUISHABLE FROM OTHER CANCERS

e.g

ARSENIC

THE ARGUMENTS APPLY

TO

ANY CARCINOGEN

Arsenic risk

• Skin lesions may be unique

• There may be a threshold at

• 50 -150 ppb

• (Data from Taiwan and also from Inner Mongolia)

• BUT

• Internal cancers may be different

Is there a Threshold?

• For a common cancer (lung cancer) a threshold is hard to prove because at 50 ppb a 1% risk is in the background

• For a common cancer the Peto argument applies

Toxicologists like Thresholds

• Few (if any) toxicologists address the Peto argument.

• ?? Threshold for bladder cancer and not for lung cancer??

• ED01 data on 2 DAA

• linear for liver

• threshold for bladder

• anticarcarcinogen for others

• WHY IS THERE SO MUCH CANCER IF EVERYTHING HAS A THRESHOLD?

Many Legislators still want

< 1 in a million!Where does this leave regulation

of arsenic?

Limits should be 5 ppt!

(not practical)

Arsenic risk

• For internal cancers

• At 500 ppb Measured Risk

• (Chile) is 10%

• If linear,

• risk is one in a million

• at 5 parts per trillion!!

• “background” is about

• 2 parts per billion

NOTHING SAID ABOVE SAYS THAT

THE MEDICAL OUTCOME IS CANCER

it applies to all

chronic effects

Reduction in lung function caused by air pollution

Many Legislators still want

< 1 in a million!

(pessimistically calculated

using LNT)

Should arsenic be treated differently from

Trichloroethylene (TCE)

(or vice versa)?

WHY?

MY CONCLUSION (REPEAT OF 20 YEARS AGO)

IT IS NOT POSSIBLE

TO REGULATE A

ONE IN A MILLION

LIFETIME RISK CONSISTENTLY

• ATTEMPTS TO DO SO • ARE

• ARBITRARY

• and

• CAPRICIOUS

How should we dispose of ARSENIC?

1970 Spray 40,000 tons a year

on our crops and forget it!

WHY NOT TREAT IT LIKE LONG LIVED HIGH LEVEL

NUCLEAR WASTE?

Equally likely for LNT to apply

MUCH more ARSENIC

than nuclear waste

(Cohen 1977 Revs. Mod Phys)

How should we dispose of ARSENIC? (contd)

EPA says that Arsenic need not be put in a secure landfill.

BUT

If the proposed EPA regulations for Yucca Mountain are applied

No water system in USA and not much agricultural land would be in compliance.

Unreasonable consistency is the

hobgoblin of small minds(Emerson)

BUT Regulators have a duty

(rarely performed)

to explain each inconsistency

This duty is even bigger

for the

National Academy of Sciences

Can One Prove a threshold?

MAYBE

if one focusses on the right question:

Similarity to

Asbestos

Benzene

Can One Prove a threshold? (2)

MEREWEATHER”S QUESTION (1937)

Is it ASBESTOS or is it the ASBESTOSIS that is

caused by asbestos that causes the lung cancers?

If the former LNT is likely

If the latter LNT is less likely

Can One Prove a threshold? (3)

There semes to be a threshold for

SKIN LESIONS

(should be studied further)

Are lung cancers more or less likely if there are skin

lesions?

(Allan Smith may tell us)

Can One Prove a threshold? (4)

Are the lung cancers really indistinguishable from background cancers?

If NOT Peto’s argument does not apply

Try DNA matching on lung tumor samples.

Similarly for asbestos cancers, radiation leukemias etc.